[[mvc-view]]
= View Technologies
[.small]#<<web-reactive.adoc#webflux-view,Same in Spring WebFlux>>#

The use of view technologies in Spring MVC is pluggable, whether you decide to
use Thymeleaf, Groovy Markup Templates, JSPs, or other, is primarily a matter of a
configuration change. This chapter covers view technologies integrated with Spring MVC.
We assume you are already familiar with <<mvc-viewresolver>>.




[[mvc-view-thymeleaf]]
== Thymeleaf
[.small]#<<web-reactive.adoc#webflux-view-thymeleaf,Same in Spring WebFlux>>#

Thymeleaf is modern server-side Java template engine that emphasizes natural HTML
templates that can be previewed in a browser by double-clicking, which is very
helpful for independent work on UI templates, e.g. by designer, without the need for a
running server. If you're looking to replace JSPs, Thymeleaf offers one of the most
extensive set of features that will make such a transition easier. Thymeleaf is actively
developed and maintained. For a more complete introduction see the
http://www.thymeleaf.org/[Thymeleaf] project home page.

The Thymeleaf integration with Spring MVC is managed by the Thymeleaf project. The
configuration involves a few bean declarations such as
`ServletContextTemplateResolver`, `SpringTemplateEngine`, and `ThymeleafViewResolver`.
See http://www.thymeleaf.org/documentation.html[Thymeleaf+Spring] for more details.




[[mvc-view-freemarker]]
== FreeMarker
[.small]#<<web-reactive.adoc#webflux-view-freemarker,Same in Spring WebFlux>>#

http://www.freemarker.org[Apache FreeMarker] is a template engine for generating any
kind of text output from HTML to email, and others. The Spring Framework has a built-in
integration for using Spring MVC with FreeMarker templates.



[[mvc-view-freemarker-contextconfig]]
=== View config
[.small]#<<web-reactive.adoc#webflux-view-freemarker-contextconfig,Same in Spring WebFlux>>#

To configure FreeMarker as a view technology:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

		@Override
		public void configureViewResolvers(ViewResolverRegistry registry) {
			registry.freemarker();
		}

		// Configure FreeMarker...

		@Bean
		public FreeMarkerConfigurer freeMarkerConfigurer() {
			FreeMarkerConfigurer configurer = new FreeMarkerConfigurer();
			configurer.setTemplateLoaderPath("/WEB-INF/freemarker");
			return configurer;
		}
	}
----

To configure the same in XML:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<mvc:annotation-driven/>

	<mvc:view-resolvers>
		<mvc:freemarker/>
	</mvc:view-resolvers>

	<!-- Configure FreeMarker... -->
	<mvc:freemarker-configurer>
		<mvc:template-loader-path location="/WEB-INF/freemarker"/>
	</mvc:freemarker-configurer>
----

Or you can also declare the `FreeMarkerConfigurer` bean for full control over all
properties:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
		<property name="templateLoaderPath" value="/WEB-INF/freemarker/"/>
	</bean>
----

Your templates need to be stored in the directory specified by the `FreeMarkerConfigurer`
shown above. Given the above configuration if your controller returns the view name
"welcome" then the resolver will look for the `/WEB-INF/freemarker/welcome.ftl` template.


[[mvc-views-freemarker]]
=== FreeMarker config
[.small]#<<web-reactive.adoc#webflux-views-freemarker,Same in Spring WebFlux>>#

FreeMarker 'Settings' and 'SharedVariables' can be passed directly to the FreeMarker
`Configuration` object managed by Spring by setting the appropriate bean properties on
the `FreeMarkerConfigurer` bean. The `freemarkerSettings` property requires a
`java.util.Properties` object and the `freemarkerVariables` property requires a
`java.util.Map`.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
		<property name="templateLoaderPath" value="/WEB-INF/freemarker/"/>
		<property name="freemarkerVariables">
			<map>
				<entry key="xml_escape" value-ref="fmXmlEscape"/>
			</map>
		</property>
	</bean>

	<bean id="fmXmlEscape" class="freemarker.template.utility.XmlEscape"/>
----

See the FreeMarker documentation for details of settings and variables as they apply to
the `Configuration` object.



[[mvc-view-freemarker-forms]]
=== Form handling

Spring provides a tag library for use in JSP's that contains, amongst others, a
`<spring:bind/>` tag. This tag primarily enables forms to display values from form
backing objects and to show the results of failed validations from a `Validator` in the
web or business tier. Spring also has support for the same functionality in FreeMarker,
with additional convenience macros for generating form input elements themselves.


[[mvc-view-bind-macros]]
==== The bind macros

A standard set of macros are maintained within the `spring-webmvc.jar` file for both
languages, so they are always available to a suitably configured application.

Some of the macros defined in the Spring libraries are considered internal (private) but
no such scoping exists in the macro definitions making all macros visible to calling
code and user templates. The following sections concentrate only on the macros you need
to be directly calling from within your templates. If you wish to view the macro code
directly, the file is called `spring.ftl` in the package
`org.springframework.web.servlet.view.freemarker`.


[[mvc-view-simple-binding]]
==== Simple binding

In your HTML forms (vm / ftl templates) which act as a form view for a Spring MVC
controller, you can use code similar to the following to bind to field values and
display error messages for each input field in similar fashion to the JSP equivalent.
Example code is shown below for the `personForm` view configured earlier:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<!-- freemarker macros have to be imported into a namespace. We strongly
	recommend sticking to 'spring' -->
	<#import "/spring.ftl" as spring/>
	<html>
		...
		<form action="" method="POST">
			Name:
			<@spring.bind "myModelObject.name"/>
			<input type="text"
				name="${spring.status.expression}"
				value="${spring.status.value?html}"/><br>
			<#list spring.status.errorMessages as error> <b>${error}</b> <br> </#list>
			<br>
			...
			<input type="submit" value="submit"/>
		</form>
		...
	</html>
----

`<@spring.bind>` requires a 'path' argument which consists of the name of your command
object (it will be 'command' unless you changed it in your FormController properties)
followed by a period and the name of the field on the command object you wish to bind to.
Nested fields can be used too such as "command.address.street". The `bind` macro assumes
the default HTML escaping behavior specified by the ServletContext parameter
`defaultHtmlEscape` in `web.xml`.

The optional form of the macro called `<@spring.bindEscaped>` takes a second argument
and explicitly specifies whether HTML escaping should be used in the status error
messages or values. Set to true or false as required. Additional form handling macros
simplify the use of HTML escaping and these macros should be used wherever possible.
They are explained in the next section.


[[mvc-views-form-macros]]
==== Input macros

Additional convenience macros for both languages simplify both binding and form
generation (including validation error display). It is never necessary to use these
macros to generate form input fields, and they can be mixed and matched with simple HTML
or calls direct to the spring bind macros highlighted previously.

The following table of available macros show the FTL definitions and the
parameter list that each takes.

[[views-macros-defs-tbl]]
.Table of macro definitions
[cols="3,1"]
|===
| macro | FTL definition

| **message** (output a string from a resource bundle based on the code parameter)
| <@spring.message code/>

| **messageText** (output a string from a resource bundle based on the code parameter,
  falling back to the value of the default parameter)
| <@spring.messageText code, text/>

| **url** (prefix a relative URL with the application's context root)
| <@spring.url relativeUrl/>

| **formInput** (standard input field for gathering user input)
| <@spring.formInput path, attributes, fieldType/>

| **formHiddenInput *** (hidden input field for submitting non-user input)
| <@spring.formHiddenInput path, attributes/>

| **formPasswordInput** * (standard input field for gathering passwords. Note that no
  value will ever be populated in fields of this type)
| <@spring.formPasswordInput path, attributes/>

| **formTextarea** (large text field for gathering long, freeform text input)
| <@spring.formTextarea path, attributes/>

| **formSingleSelect** (drop down box of options allowing a single required value to be
  selected)
| <@spring.formSingleSelect path, options, attributes/>

| **formMultiSelect** (a list box of options allowing the user to select 0 or more values)
| <@spring.formMultiSelect path, options, attributes/>

| **formRadioButtons** (a set of radio buttons allowing a single selection to be made
  from the available choices)
| <@spring.formRadioButtons path, options separator, attributes/>

| **formCheckboxes** (a set of checkboxes allowing 0 or more values to be selected)
| <@spring.formCheckboxes path, options, separator, attributes/>

| **formCheckbox** (a single checkbox)
| <@spring.formCheckbox path, attributes/>

| **showErrors** (simplify display of validation errors for the bound field)
| <@spring.showErrors separator, classOrStyle/>
|===

* In FTL (FreeMarker), `formHiddenInput` and `formPasswordInput` are not actually required
  as you can use the normal `formInput` macro, specifying `hidden` or `password` as the
  value for the `fieldType` parameter.

The parameters to any of the above macros have consistent meanings:

* path: the name of the field to bind to (ie "command.name")
* options: a Map of all the available values that can be selected from in the input
  field. The keys to the map represent the values that will be POSTed back from the form
  and bound to the command object. Map objects stored against the keys are the labels
  displayed on the form to the user and may be different from the corresponding values
  posted back by the form. Usually such a map is supplied as reference data by the
  controller. Any Map implementation can be used depending on required behavior. For
  strictly sorted maps, a `SortedMap` such as a `TreeMap` with a suitable Comparator may
  be used and for arbitrary Maps that should return values in insertion order, use a
  `LinkedHashMap` or a `LinkedMap` from commons-collections.
* separator: where multiple options are available as discreet elements (radio buttons or
  checkboxes), the sequence of characters used to separate each one in the list (ie
  "<br>").
* attributes: an additional string of arbitrary tags or text to be included within the
  HTML tag itself. This string is echoed literally by the macro. For example, in a
  textarea field you may supply attributes as 'rows="5" cols="60"' or you could pass
  style information such as 'style="border:1px solid silver"'.
* classOrStyle: for the showErrors macro, the name of the CSS class that the span tag
  wrapping each error will use. If no information is supplied (or the value is empty)
  then the errors will be wrapped in <b></b> tags.

Examples of the macros are outlined below some in FTL and some in VTL. Where usage
differences exist between the two languages, they are explained in the notes.

[[mvc-views-form-macros-input]]
===== Input Fields

The formInput macro takes the path parameter (command.name) and an additional attributes
parameter which is empty in the example above. The macro, along with all other form
generation macros, performs an implicit spring bind on the path parameter. The binding
remains valid until a new bind occurs so the showErrors macro doesn't need to pass the
path parameter again - it simply operates on whichever field a bind was last created for.

The showErrors macro takes a separator parameter (the characters that will be used to
separate multiple errors on a given field) and also accepts a second parameter, this
time a class name or style attribute. Note that FreeMarker is able to specify default
values for the attributes parameter.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<@spring.formInput "command.name"/>
	<@spring.showErrors "<br>"/>
----

Output is shown below of the form fragment generating the name field, and displaying a
validation error after the form was submitted with no value in the field. Validation
occurs through Spring's Validation framework.

The generated HTML looks like this:

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	Name:
	<input type="text" name="name" value="">
	<br>
		<b>required</b>
	<br>
	<br>
----

The formTextarea macro works the same way as the formInput macro and accepts the same
parameter list. Commonly, the second parameter (attributes) will be used to pass style
information or rows and cols attributes for the textarea.

[[mvc-views-form-macros-select]]
===== Selection Fields

Four selection field macros can be used to generate common UI value selection inputs in
your HTML forms.

* formSingleSelect
* formMultiSelect
* formRadioButtons
* formCheckboxes

Each of the four macros accepts a Map of options containing the value for the form
field, and the label corresponding to that value. The value and the label can be the
same.

An example of radio buttons in FTL is below. The form backing object specifies a default
value of 'London' for this field and so no validation is necessary. When the form is
rendered, the entire list of cities to choose from is supplied as reference data in the
model under the name 'cityMap'.

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	...
	Town:
	<@spring.formRadioButtons "command.address.town", cityMap, ""/><br><br>
----

This renders a line of radio buttons, one for each value in `cityMap` using the
separator "". No additional attributes are supplied (the last parameter to the macro is
missing). The cityMap uses the same String for each key-value pair in the map. The map's
keys are what the form actually submits as POSTed request parameters, map values are the
labels that the user sees. In the example above, given a list of three well known cities
and a default value in the form backing object, the HTML would be

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	Town:
	<input type="radio" name="address.town" value="London">London</input>
	<input type="radio" name="address.town" value="Paris" checked="checked">Paris</input>
	<input type="radio" name="address.town" value="New York">New York</input>
----

If your application expects to handle cities by internal codes for example, the map of
codes would be created with suitable keys like the example below.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	protected Map<String, String> referenceData(HttpServletRequest request) throws Exception {
		Map<String, String> cityMap = new LinkedHashMap<>();
		cityMap.put("LDN", "London");
		cityMap.put("PRS", "Paris");
		cityMap.put("NYC", "New York");

		Map<String, String> model = new HashMap<>();
		model.put("cityMap", cityMap);
		return model;
	}
----

The code would now produce output where the radio values are the relevant codes but the
user still sees the more user friendly city names.

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	Town:
	<input type="radio" name="address.town" value="LDN">London</input>
	<input type="radio" name="address.town" value="PRS" checked="checked">Paris</input>
	<input type="radio" name="address.town" value="NYC">New York</input>
----


[[mvc-views-form-macros-html-escaping]]
==== HTML escaping

Default usage of the form macros above will result in HTML tags that are HTML 4.01
compliant and that use the default value for HTML escaping defined in your web.xml as
used by Spring's bind support. In order to make the tags XHTML compliant or to override
the default HTML escaping value, you can specify two variables in your template (or in
your model where they will be visible to your templates). The advantage of specifying
them in the templates is that they can be changed to different values later in the
template processing to provide different behavior for different fields in your form.

To switch to XHTML compliance for your tags, specify a value of `true` for a
model/context variable named xhtmlCompliant:

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	<#-- for FreeMarker -->
	<#assign xhtmlCompliant = true>
----

Any tags generated by the Spring macros will now be XHTML compliant after processing
this directive.

In similar fashion, HTML escaping can be specified per field:

[source,jsp,indent=0]
[subs="verbatim,quotes"]
----
	<#-- until this point, default HTML escaping is used -->

	<#assign htmlEscape = true>
	<#-- next field will use HTML escaping -->
	<@spring.formInput "command.name"/>

	<#assign htmlEscape = false in spring>
	<#-- all future fields will be bound with HTML escaping off -->
----




[[mvc-view-groovymarkup]]
== Groovy Markup

http://groovy-lang.org/templating.html#_the_markuptemplateengine[Groovy Markup Template Engine]
is primarily aimed at generating XML-like markup (XML, XHTML, HTML5, etc) but that can
be used to generate any text based content. The Spring Framework has a built-in
integration for using Spring MVC with Groovy Markup.

[TIP]
====
The Groovy Markup Tempalte engine requires Groovy 2.3.1+.
====



[[mvc-view-groovymarkup-configuration]]
=== Configuration

To configure the Groovy Markup Template Engine:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

		@Override
		public void configureViewResolvers(ViewResolverRegistry registry) {
			registry.groovy();
		}

		// Configure the Groovy Markup Template Engine...

		@Bean
		public GroovyMarkupConfigurer groovyMarkupConfigurer() {
			GroovyMarkupConfigurer configurer = new GroovyMarkupConfigurer();
			configurer.setResourceLoaderPath("/WEB-INF/");
			return configurer;
		}
	}
----

To configure the same in XML:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<mvc:annotation-driven/>

	<mvc:view-resolvers>
		<mvc:groovy/>
	</mvc:view-resolvers>

	<!-- Configure the Groovy Markup Template Engine... -->
	<mvc:groovy-configurer resource-loader-path="/WEB-INF/"/>
----



[[mvc-view-groovymarkup-example]]
=== Example

Unlike traditional template engines, Groovy Markup relies on a DSL that uses a builder
syntax. Here is a sample template for an HTML page:

[source,groovy,indent=0]
[subs="verbatim,quotes"]
----
	yieldUnescaped '<!DOCTYPE html>'
	html(lang:'en') {
		head {
			meta('http-equiv':'"Content-Type" content="text/html; charset=utf-8"')
			title('My page')
		}
		body {
			p('This is an example of HTML contents')
		}
	}
----




[[mvc-view-script]]
== Script Views
[.small]#<<web-reactive.adoc#webflux-view-script,Same in Spring WebFlux>>#

The Spring Framework has a built-in integration for using Spring MVC with any
templating library that can run on top of the
https://www.jcp.org/en/jsr/detail?id=223[JSR-223] Java scripting engine. Below is a list
of templating libraries we've tested on different script engines:

[horizontal]
http://handlebarsjs.com/[Handlebars] :: http://openjdk.java.net/projects/nashorn/[Nashorn]
https://mustache.github.io/[Mustache] :: http://openjdk.java.net/projects/nashorn/[Nashorn]
http://facebook.github.io/react/[React] :: http://openjdk.java.net/projects/nashorn/[Nashorn]
http://www.embeddedjs.com/[EJS] :: http://openjdk.java.net/projects/nashorn/[Nashorn]
http://www.stuartellis.eu/articles/erb/[ERB] :: http://jruby.org[JRuby]
https://docs.python.org/2/library/string.html#template-strings[String templates] :: http://www.jython.org/[Jython]
https://github.com/sdeleuze/kotlin-script-templating[Kotlin Script templating] :: http://kotlinlang.org/[Kotlin]

[TIP]
====
The basic rule for integrating any other script engine is that it must implement the
`ScriptEngine` and `Invocable` interfaces.
====



[[mvc-view-script-dependencies]]
=== Requirements
[.small]#<<web-reactive.adoc#webflux-view-script-dependencies,Same in Spring WebFlux>>#

You need to have the script engine on your classpath:

* http://openjdk.java.net/projects/nashorn/[Nashorn] JavaScript engine is provided with
Java 8+. Using the latest update release available is highly recommended.
* http://jruby.org[JRuby] should be added as a dependency for Ruby support.
* http://www.jython.org[Jython] should be added as a dependency for Python support.
* `org.jetbrains.kotlin:kotlin-script-util` dependency and a `META-INF/services/javax.script.ScriptEngineFactory`
 file containing a `org.jetbrains.kotlin.script.jsr223.KotlinJsr223JvmLocalScriptEngineFactory`
 line should be added for Kotlin script support, see
 https://github.com/sdeleuze/kotlin-script-templating[this example] for more details.

You need to have the script templating library. One way to do that for Javascript is
through http://www.webjars.org/[WebJars].



[[mvc-view-script-integrate]]
=== Script templates
[.small]#<<web-reactive.adoc#webflux-script-integrate,Same in Spring WebFlux>>#

Declare a `ScriptTemplateConfigurer` bean in order to specify the script engine to use,
the script files to load, what function to call to render templates, and so on.
Below is an example with Mustache templates and the Nashorn JavaScript engine:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

		@Override
		public void configureViewResolvers(ViewResolverRegistry registry) {
			registry.scriptTemplate();
		}

		@Bean
		public ScriptTemplateConfigurer configurer() {
			ScriptTemplateConfigurer configurer = new ScriptTemplateConfigurer();
			configurer.setEngineName("nashorn");
			configurer.setScripts("mustache.js");
			configurer.setRenderObject("Mustache");
			configurer.setRenderFunction("render");
			return configurer;
		}
	}
----

The same in XML:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<mvc:annotation-driven/>

	<mvc:view-resolvers>
		<mvc:script-template/>
	</mvc:view-resolvers>

	<mvc:script-template-configurer engine-name="nashorn" render-object="Mustache" render-function="render">
		<mvc:script location="mustache.js"/>
	</mvc:script-template-configurer>
----

The controller would look no different:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Controller
	public class SampleController {

		@GetMapping("/sample")
		public String test(Model model) {
			model.addObject("title", "Sample title");
			model.addObject("body", "Sample body");
			return "template";
		}
	}
----

And the Mustache template is:

[source,html,indent=0]
[subs="verbatim,quotes"]
----
	<html>
		<head>
			<title>{{title}}</title>
		</head>
		<body>
			<p>{{body}}</p>
		</body>
	</html>
----

The render function is called with the following parameters:

* `String template`: the template content
* `Map model`: the view model
* `RenderingContext renderingContext`: the
  {api-spring-framework}/web/servlet/view/script/RenderingContext.html[RenderingContext]
  that gives access to the application context, the locale, the template loader and the
  url (since 5.0)

`Mustache.render()` is natively compatible with this signature, so you can call it directly.

If your templating technology requires some customization, you may provide a script that
implements a custom render function. For example, http://handlebarsjs.com[Handlerbars]
needs to compile templates before using them, and requires a
http://en.wikipedia.org/wiki/Polyfill[polyfill] in order to emulate some
browser facilities not available in the server-side script engine.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

		@Override
		public void configureViewResolvers(ViewResolverRegistry registry) {
			registry.scriptTemplate();
		}

		@Bean
		public ScriptTemplateConfigurer configurer() {
			ScriptTemplateConfigurer configurer = new ScriptTemplateConfigurer();
			configurer.setEngineName("nashorn");
			configurer.setScripts("polyfill.js", "handlebars.js", "render.js");
			configurer.setRenderFunction("render");
			configurer.setSharedEngine(false);
			return configurer;
		}
	}
----

[NOTE]
====
Setting the `sharedEngine` property to `false` is required when using non thread-safe
script engines with templating libraries not designed for concurrency, like Handlebars or
React running on Nashorn for example. In that case, Java 8u60 or greater is required due
to https://bugs.openjdk.java.net/browse/JDK-8076099[this bug].
====

`polyfill.js` only defines the `window` object needed by Handlebars to run properly:

[source,javascript,indent=0]
[subs="verbatim,quotes"]
----
	var window = {};
----

This basic `render.js` implementation compiles the template before using it. A production
ready implementation should also store and reused cached templates / pre-compiled templates.
This can be done on the script side, as well as any customization you need (managing
template engine configuration for example).

[source,javascript,indent=0]
[subs="verbatim,quotes"]
----
	function render(template, model) {
		var compiledTemplate = Handlebars.compile(template);
		return compiledTemplate(model);
	}
----

Check out the Spring Framework unit tests,
https://github.com/spring-projects/spring-framework/tree/master/spring-webmvc/src/test/java/org/springframework/web/servlet/view/script[java], and
https://github.com/spring-projects/spring-framework/tree/master/spring-webmvc/src/test/resources/org/springframework/web/servlet/view/script[resources],
for more configuration examples.




[[mvc-view-jsp]]
== JSP & JSTL

The Spring Framework has a built-in integration for using Spring MVC with JSP and JSTL.



[[mvc-view-jsp-resolver]]
=== View resolvers

When developing with JSPs you can declare a `InternalResourceViewResolver` or a
`ResourceBundleViewResolver` bean.

`ResourceBundleViewResolver` relies on a properties file to define the view names
mapped to a class and a URL. With a `ResourceBundleViewResolver` you
can mix different types of views using only one resolver. Here is an example:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<!-- the ResourceBundleViewResolver -->
	<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
		<property name="basename" value="views"/>
	</bean>

	# And a sample properties file is uses (views.properties in WEB-INF/classes):
	welcome.(class)=org.springframework.web.servlet.view.JstlView
	welcome.url=/WEB-INF/jsp/welcome.jsp

	productList.(class)=org.springframework.web.servlet.view.JstlView
	productList.url=/WEB-INF/jsp/productlist.jsp
----

`InternalResourceBundleViewResolver` can also be used for JSPs. As a best practice, we
strongly encourage placing your JSP files in a directory under the `'WEB-INF'`
directory so there can be no direct access by clients.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
		<property name="prefix" value="/WEB-INF/jsp/"/>
		<property name="suffix" value=".jsp"/>
	</bean>
----



[[mvc-view-jsp-jstl]]
=== JSPs versus JSTL

When using the Java Standard Tag Library you must use a special view class, the
`JstlView`, as JSTL needs some preparation before things such as the I18N features will
work.



[[mvc-view-jsp-tags]]
=== Spring's JSP tag library

Spring provides data binding of request parameters to command objects as described in
earlier chapters. To facilitate the development of JSP pages in combination with those
data binding features, Spring provides a few tags that make things even easier. All
Spring tags have__HTML escaping__ features to enable or disable escaping of characters.

The `spring.tld` tag library descriptor (TLD) is included in the `spring-webmvc.jar`.
For a comprehensive reference on individual tags, browse the
{api-spring-framework}/web/servlet/tags/package-summary.html#package.description[API reference]
or see the tag library description.


[[mvc-view-jsp-formtaglib]]
=== Spring's form tag library

As of version 2.0, Spring provides a comprehensive set of data binding-aware tags for
handling form elements when using JSP and Spring Web MVC. Each tag provides support for
the set of attributes of its corresponding HTML tag counterpart, making the tags
familiar and intuitive to use. The tag-generated HTML is HTML 4.01/XHTML 1.0 compliant.

Unlike other form/input tag libraries, Spring's form tag library is integrated with
Spring Web MVC, giving the tags access to the command object and reference data your
controller deals with. As you will see in the following examples, the form tags make
JSPs easier to develop, read and maintain.

Let's go through the form tags and look at an example of how each tag is used. We have
included generated HTML snippets where certain tags require further commentary.


[[mvc-view-jsp-formtaglib-configuration]]
==== Configuration

The form tag library comes bundled in `spring-webmvc.jar`. The library descriptor is
called `spring-form.tld`.

To use the tags from this library, add the following directive to the top of your JSP
page:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
----

where `form` is the tag name prefix you want to use for the tags from this library.


[[mvc-view-jsp-formtaglib-formtag]]
==== The form tag

This tag renders an HTML 'form' tag and exposes a binding path to inner tags for
binding. It puts the command object in the `PageContext` so that the command object can
be accessed by inner tags. __All the other tags in this library are nested tags of the
`form` tag__.

Let's assume we have a domain object called `User`. It is a JavaBean with properties
such as `firstName` and `lastName`. We will use it as the form backing object of our
form controller which returns `form.jsp`. Below is an example of what `form.jsp` would
look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form>
		<table>
			<tr>
				<td>First Name:</td>
				<td><form:input path="firstName"/></td>
			</tr>
			<tr>
				<td>Last Name:</td>
				<td><form:input path="lastName"/></td>
			</tr>
			<tr>
				<td colspan="2">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form:form>
----

The `firstName` and `lastName` values are retrieved from the command object placed in
the `PageContext` by the page controller. Keep reading to see more complex examples of
how inner tags are used with the `form` tag.

The generated HTML looks like a standard form:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form method="POST">
		<table>
			<tr>
				<td>First Name:</td>
				<td><input name="firstName" type="text" value="Harry"/></td>
			</tr>
			<tr>
				<td>Last Name:</td>
				<td><input name="lastName" type="text" value="Potter"/></td>
			</tr>
			<tr>
				<td colspan="2">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form>
----

The preceding JSP assumes that the variable name of the form backing object is
`'command'`. If you have put the form backing object into the model under another name
(definitely a best practice), then you can bind the form to the named variable like so:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form modelAttribute="user">
		<table>
			<tr>
				<td>First Name:</td>
				<td><form:input path="firstName"/></td>
			</tr>
			<tr>
				<td>Last Name:</td>
				<td><form:input path="lastName"/></td>
			</tr>
			<tr>
				<td colspan="2">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form:form>
----


[[mvc-view-jsp-formtaglib-inputtag]]
==== The input tag

This tag renders an HTML 'input' tag using the bound value and type='text' by default.
For an example of this tag, see <<mvc-view-jsp-formtaglib-formtag>>. Starting with Spring
3.1 you can use other types such HTML5-specific types like 'email', 'tel', 'date', and
others.


[[mvc-view-jsp-formtaglib-checkboxtag]]
==== The checkbox tag

This tag renders an HTML 'input' tag with type 'checkbox'.

Let's assume our `User` has preferences such as newsletter subscription and a list of
hobbies. Below is an example of the `Preferences` class:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	public class Preferences {

		private boolean receiveNewsletter;
		private String[] interests;
		private String favouriteWord;

		public boolean isReceiveNewsletter() {
			return receiveNewsletter;
		}

		public void setReceiveNewsletter(boolean receiveNewsletter) {
			this.receiveNewsletter = receiveNewsletter;
		}

		public String[] getInterests() {
			return interests;
		}

		public void setInterests(String[] interests) {
			this.interests = interests;
		}

		public String getFavouriteWord() {
			return favouriteWord;
		}

		public void setFavouriteWord(String favouriteWord) {
			this.favouriteWord = favouriteWord;
		}
	}
----

The `form.jsp` would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form>
		<table>
			<tr>
				<td>Subscribe to newsletter?:</td>
				<%-- Approach 1: Property is of type java.lang.Boolean --%>
				<td><form:checkbox path="preferences.receiveNewsletter"/></td>
			</tr>

			<tr>
				<td>Interests:</td>
				<%-- Approach 2: Property is of an array or of type java.util.Collection --%>
				<td>
					Quidditch: <form:checkbox path="preferences.interests" value="Quidditch"/>
					Herbology: <form:checkbox path="preferences.interests" value="Herbology"/>
					Defence Against the Dark Arts: <form:checkbox path="preferences.interests" value="Defence Against the Dark Arts"/>
				</td>
			</tr>

			<tr>
				<td>Favourite Word:</td>
				<%-- Approach 3: Property is of type java.lang.Object --%>
				<td>
					Magic: <form:checkbox path="preferences.favouriteWord" value="Magic"/>
				</td>
			</tr>
		</table>
	</form:form>
----

There are 3 approaches to the `checkbox` tag which should meet all your checkbox needs.

* Approach One - When the bound value is of type `java.lang.Boolean`, the
  `input(checkbox)` is marked as 'checked' if the bound value is `true`. The `value`
  attribute corresponds to the resolved value of the `setValue(Object)` value property.
* Approach Two - When the bound value is of type `array` or `java.util.Collection`, the
  `input(checkbox)` is marked as 'checked' if the configured `setValue(Object)` value is
  present in the bound `Collection`.
* Approach Three - For any other bound value type, the `input(checkbox)` is marked as
  'checked' if the configured `setValue(Object)` is equal to the bound value.

Note that regardless of the approach, the same HTML structure is generated. Below is an
HTML snippet of some checkboxes:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Interests:</td>
		<td>
			Quidditch: <input name="preferences.interests" type="checkbox" value="Quidditch"/>
			<input type="hidden" value="1" name="_preferences.interests"/>
			Herbology: <input name="preferences.interests" type="checkbox" value="Herbology"/>
			<input type="hidden" value="1" name="_preferences.interests"/>
			Defence Against the Dark Arts: <input name="preferences.interests" type="checkbox" value="Defence Against the Dark Arts"/>
			<input type="hidden" value="1" name="_preferences.interests"/>
		</td>
	</tr>
----

What you might not expect to see is the additional hidden field after each checkbox.
When a checkbox in an HTML page is __not__ checked, its value will not be sent to the
server as part of the HTTP request parameters once the form is submitted, so we need a
workaround for this quirk in HTML in order for Spring form data binding to work. The
`checkbox` tag follows the existing Spring convention of including a hidden parameter
prefixed by an underscore ("_") for each checkbox. By doing this, you are effectively
telling Spring that "__the checkbox was visible in the form and I want my object to
which the form data will be bound to reflect the state of the checkbox no matter what__".


[[mvc-view-jsp-formtaglib-checkboxestag]]
==== The checkboxes tag

This tag renders multiple HTML 'input' tags with type 'checkbox'.

Building on the example from the previous `checkbox` tag section. Sometimes you prefer
not to have to list all the possible hobbies in your JSP page. You would rather provide
a list at runtime of the available options and pass that in to the tag. That is the
purpose of the `checkboxes` tag. You pass in an `Array`, a `List` or a `Map` containing
the available options in the "items" property. Typically the bound property is a
collection so it can hold multiple values selected by the user. Below is an example of
the JSP using this tag:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form>
		<table>
			<tr>
				<td>Interests:</td>
				<td>
					<%-- Property is of an array or of type java.util.Collection --%>
					<form:checkboxes path="preferences.interests" items="${interestList}"/>
				</td>
			</tr>
		</table>
	</form:form>
----

This example assumes that the "interestList" is a `List` available as a model attribute
containing strings of the values to be selected from. In the case where you use a Map,
the map entry key will be used as the value and the map entry's value will be used as
the label to be displayed. You can also use a custom object where you can provide the
property names for the value using "itemValue" and the label using "itemLabel".


[[mvc-view-jsp-formtaglib-radiobuttontag]]
==== The radiobutton tag

This tag renders an HTML 'input' tag with type 'radio'.

A typical usage pattern will involve multiple tag instances bound to the same property
but with different values.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Sex:</td>
		<td>
			Male: <form:radiobutton path="sex" value="M"/> <br/>
			Female: <form:radiobutton path="sex" value="F"/>
		</td>
	</tr>
----


[[mvc-view-jsp-formtaglib-radiobuttonstag]]
==== The radiobuttons tag

This tag renders multiple HTML 'input' tags with type 'radio'.

Just like the `checkboxes` tag above, you might want to pass in the available options as
a runtime variable. For this usage you would use the `radiobuttons` tag. You pass in an
`Array`, a `List` or a `Map` containing the available options in the "items" property.
In the case where you use a Map, the map entry key will be used as the value and the map
entry's value will be used as the label to be displayed. You can also use a custom
object where you can provide the property names for the value using "itemValue" and the
label using "itemLabel".

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Sex:</td>
		<td><form:radiobuttons path="sex" items="${sexOptions}"/></td>
	</tr>
----


[[mvc-view-jsp-formtaglib-passwordtag]]
==== The password tag

This tag renders an HTML 'input' tag with type 'password' using the bound value.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Password:</td>
		<td>
			<form:password path="password"/>
		</td>
	</tr>
----

Please note that by default, the password value is __not__ shown. If you do want the
password value to be shown, then set the value of the `'showPassword'` attribute to
true, like so.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Password:</td>
		<td>
			<form:password path="password" value="^76525bvHGq" showPassword="true"/>
		</td>
	</tr>
----


[[mvc-view-jsp-formtaglib-selecttag]]
==== The select tag

This tag renders an HTML 'select' element. It supports data binding to the selected
option as well as the use of nested `option` and `options` tags.

Let's assume a `User` has a list of skills.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Skills:</td>
		<td><form:select path="skills" items="${skills}"/></td>
	</tr>
----

If the `User's` skill were in Herbology, the HTML source of the 'Skills' row would look
like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Skills:</td>
		<td>
			<select name="skills" multiple="true">
				<option value="Potions">Potions</option>
				<option value="Herbology" selected="selected">Herbology</option>
				<option value="Quidditch">Quidditch</option>
			</select>
		</td>
	</tr>
----


[[mvc-view-jsp-formtaglib-optiontag]]
==== The option tag

This tag renders an HTML 'option'. It sets 'selected' as appropriate based on the bound
value.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>House:</td>
		<td>
			<form:select path="house">
				<form:option value="Gryffindor"/>
				<form:option value="Hufflepuff"/>
				<form:option value="Ravenclaw"/>
				<form:option value="Slytherin"/>
			</form:select>
		</td>
	</tr>
----

If the `User's` house was in Gryffindor, the HTML source of the 'House' row would look
like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>House:</td>
		<td>
			<select name="house">
				<option value="Gryffindor" selected="selected">Gryffindor</option>
				<option value="Hufflepuff">Hufflepuff</option>
				<option value="Ravenclaw">Ravenclaw</option>
				<option value="Slytherin">Slytherin</option>
			</select>
		</td>
	</tr>
----


[[mvc-view-jsp-formtaglib-optionstag]]
==== The options tag

This tag renders a list of HTML 'option' tags. It sets the 'selected' attribute as
appropriate based on the bound value.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Country:</td>
		<td>
			<form:select path="country">
				<form:option value="-" label="--Please Select"/>
				<form:options items="${countryList}" itemValue="code" itemLabel="name"/>
			</form:select>
		</td>
	</tr>
----

If the `User` lived in the UK, the HTML source of the 'Country' row would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Country:</td>
		<td>
			<select name="country">
				<option value="-">--Please Select</option>
				<option value="AT">Austria</option>
				<option value="UK" selected="selected">United Kingdom</option>
				<option value="US">United States</option>
			</select>
		</td>
	</tr>
----

As the example shows, the combined usage of an `option` tag with the `options` tag
generates the same standard HTML, but allows you to explicitly specify a value in the
JSP that is for display only (where it belongs) such as the default string in the
example: "-- Please Select".

The `items` attribute is typically populated with a collection or array of item objects.
`itemValue` and `itemLabel` simply refer to bean properties of those item objects, if
specified; otherwise, the item objects themselves will be stringified. Alternatively,
you may specify a `Map` of items, in which case the map keys are interpreted as option
values and the map values correspond to option labels. If `itemValue` and/or `itemLabel`
happen to be specified as well, the item value property will apply to the map key and
the item label property will apply to the map value.


[[mvc-view-jsp-formtaglib-textareatag]]
==== The textarea tag

This tag renders an HTML 'textarea'.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<tr>
		<td>Notes:</td>
		<td><form:textarea path="notes" rows="3" cols="20"/></td>
		<td><form:errors path="notes"/></td>
	</tr>
----


[[mvc-view-jsp-formtaglib-hiddeninputtag]]
==== The hidden tag

This tag renders an HTML 'input' tag with type 'hidden' using the bound value. To submit
an unbound hidden value, use the HTML `input` tag with type 'hidden'.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:hidden path="house"/>

----

If we choose to submit the 'house' value as a hidden one, the HTML would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<input name="house" type="hidden" value="Gryffindor"/>

----


[[mvc-view-jsp-formtaglib-errorstag]]
==== The errors tag

This tag renders field errors in an HTML 'span' tag. It provides access to the errors
created in your controller or those that were created by any validators associated with
your controller.

Let's assume we want to display all error messages for the `firstName` and `lastName`
fields once we submit the form. We have a validator for instances of the `User` class
called `UserValidator`.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	public class UserValidator implements Validator {

		public boolean supports(Class candidate) {
			return User.class.isAssignableFrom(candidate);
		}

		public void validate(Object obj, Errors errors) {
			ValidationUtils.rejectIfEmptyOrWhitespace(errors, "firstName", "required", "Field is required.");
			ValidationUtils.rejectIfEmptyOrWhitespace(errors, "lastName", "required", "Field is required.");
		}
	}
----

The `form.jsp` would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form>
		<table>
			<tr>
				<td>First Name:</td>
				<td><form:input path="firstName"/></td>
				<%-- Show errors for firstName field --%>
				<td><form:errors path="firstName"/></td>
			</tr>

			<tr>
				<td>Last Name:</td>
				<td><form:input path="lastName"/></td>
				<%-- Show errors for lastName field --%>
				<td><form:errors path="lastName"/></td>
			</tr>
			<tr>
				<td colspan="3">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form:form>
----

If we submit a form with empty values in the `firstName` and `lastName` fields, this is
what the HTML would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form method="POST">
		<table>
			<tr>
				<td>First Name:</td>
				<td><input name="firstName" type="text" value=""/></td>
				<%-- Associated errors to firstName field displayed --%>
				<td><span name="firstName.errors">Field is required.</span></td>
			</tr>

			<tr>
				<td>Last Name:</td>
				<td><input name="lastName" type="text" value=""/></td>
				<%-- Associated errors to lastName field displayed --%>
				<td><span name="lastName.errors">Field is required.</span></td>
			</tr>
			<tr>
				<td colspan="3">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form>
----

What if we want to display the entire list of errors for a given page? The example below
shows that the `errors` tag also supports some basic wildcarding functionality.

* `path="{asterisk}"` - displays all errors
* `path="lastName"` - displays all errors associated with the `lastName` field
* if `path` is omitted - object errors only are displayed

The example below will display a list of errors at the top of the page, followed by
field-specific errors next to the fields:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form>
		<form:errors path="*" cssClass="errorBox"/>
		<table>
			<tr>
				<td>First Name:</td>
				<td><form:input path="firstName"/></td>
				<td><form:errors path="firstName"/></td>
			</tr>
			<tr>
				<td>Last Name:</td>
				<td><form:input path="lastName"/></td>
				<td><form:errors path="lastName"/></td>
			</tr>
			<tr>
				<td colspan="3">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form:form>
----

The HTML would look like:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form method="POST">
		<span name="*.errors" class="errorBox">Field is required.<br/>Field is required.</span>
		<table>
			<tr>
				<td>First Name:</td>
				<td><input name="firstName" type="text" value=""/></td>
				<td><span name="firstName.errors">Field is required.</span></td>
			</tr>

			<tr>
				<td>Last Name:</td>
				<td><input name="lastName" type="text" value=""/></td>
				<td><span name="lastName.errors">Field is required.</span></td>
			</tr>
			<tr>
				<td colspan="3">
					<input type="submit" value="Save Changes"/>
				</td>
			</tr>
		</table>
	</form>
----

The `spring-form.tld` tag library descriptor (TLD) is included in the `spring-webmvc.jar`.
For a comprehensive reference on individual tags, browse the
{api-spring-framework}/web/servlet/tags/form/package-summary.html#package.description[API reference]
or see the tag library description.


[[mvc-rest-method-conversion]]
==== HTTP method conversion

A key principle of REST is the use of the Uniform Interface. This means that all
resources (URLs) can be manipulated using the same four HTTP methods: GET, PUT, POST,
and DELETE. For each method, the HTTP specification defines the exact semantics. For
instance, a GET should always be a safe operation, meaning that is has no side effects,
and a PUT or DELETE should be idempotent, meaning that you can repeat these operations
over and over again, but the end result should be the same. While HTTP defines these
four methods, HTML only supports two: GET and POST. Fortunately, there are two possible
workarounds: you can either use JavaScript to do your PUT or DELETE, or simply do a POST
with the 'real' method as an additional parameter (modeled as a hidden input field in an
HTML form). This latter trick is what Spring's `HiddenHttpMethodFilter` does. This
filter is a plain Servlet Filter and therefore it can be used in combination with any
web framework (not just Spring MVC). Simply add this filter to your web.xml, and a POST
with a hidden _method parameter will be converted into the corresponding HTTP method
request.

To support HTTP method conversion the Spring MVC form tag was updated to support setting
the HTTP method. For example, the following snippet taken from the updated Petclinic
sample

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<form:form method="delete">
		<p class="submit"><input type="submit" value="Delete Pet"/></p>
	</form:form>
----

This will actually perform an HTTP POST, with the 'real' DELETE method hidden behind a
request parameter, to be picked up by the `HiddenHttpMethodFilter`, as defined in
web.xml:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	<filter>
		<filter-name>httpMethodFilter</filter-name>
		<filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
	</filter>

	<filter-mapping>
		<filter-name>httpMethodFilter</filter-name>
		<servlet-name>petclinic</servlet-name>
	</filter-mapping>
----

The corresponding `@Controller` method is shown below:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@RequestMapping(method = RequestMethod.DELETE)
	public String deletePet(@PathVariable int ownerId, @PathVariable int petId) {
		this.clinic.deletePet(petId);
		return "redirect:/owners/" + ownerId;
	}
----


[[mvc-view-jsp-formtaglib-html5]]
==== HTML5 tags

Starting with Spring 3, the Spring form tag library allows entering dynamic attributes,
which means you can enter any HTML5 specific attributes.

In Spring 3.1, the form input tag supports entering a type attribute other than 'text'.
This is intended to allow rendering new HTML5 specific input types such as 'email',
'date', 'range', and others. Note that entering type='text' is not required since 'text'
is the default type.




[[mvc-view-tiles]]
== Tiles

It is possible to integrate Tiles - just as any other view technology - in web
applications using Spring. The following describes in a broad way how to do this.

[NOTE]
====
This section focuses on Spring's support for Tiles v3 in the
`org.springframework.web.servlet.view.tiles3` package.
====



[[mvc-view-tiles-dependencies]]
=== Dependencies

To be able to use Tiles, you have to add a dependency on Tiles version 3.0.1 or higher
and http://tiles.apache.org/framework/dependency-management.html[its transitive dependencies]
to your project.



[[mvc-view-tiles-integrate]]
=== Configuration

To be able to use Tiles, you have to configure it using files containing definitions
(for basic information on definitions and other Tiles concepts, please have a look at
http://tiles.apache.org[]). In Spring this is done using the `TilesConfigurer`. Have a
look at the following piece of example ApplicationContext configuration:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
		<property name="definitions">
			<list>
				<value>/WEB-INF/defs/general.xml</value>
				<value>/WEB-INF/defs/widgets.xml</value>
				<value>/WEB-INF/defs/administrator.xml</value>
				<value>/WEB-INF/defs/customer.xml</value>
				<value>/WEB-INF/defs/templates.xml</value>
			</list>
		</property>
	</bean>
----

As you can see, there are five files containing definitions, which are all located in
the `'WEB-INF/defs'` directory. At initialization of the `WebApplicationContext`, the
files will be loaded and the definitions factory will be initialized. After that has
been done, the Tiles includes in the definition files can be used as views within your
Spring web application. To be able to use the views you have to have a `ViewResolver`
just as with any other view technology used with Spring. Below you can find two
possibilities, the `UrlBasedViewResolver` and the `ResourceBundleViewResolver`.

You can specify locale specific Tiles definitions by adding an underscore and then
the locale. For example:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
		<property name="definitions">
			<list>
				<value>/WEB-INF/defs/tiles.xml</value>
				<value>/WEB-INF/defs/tiles_fr_FR.xml</value>
			</list>
		</property>
	</bean>
----

With this configuration, `tiles_fr_FR.xml` will be used for requests with the `fr_FR` locale,
and `tiles.xml` will be used by default.

[NOTE]
====
Since underscores are used to indicate locales, it is recommended to avoid using
them otherwise in the file names for Tiles definitions.
====


[[mvc-view-tiles-url]]
==== UrlBasedViewResolver

The `UrlBasedViewResolver` instantiates the given `viewClass` for each view it has to
resolve.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.tiles3.TilesView"/>
	</bean>
----


[[mvc-view-tiles-resource]]
==== ResourceBundleViewResolver

The `ResourceBundleViewResolver` has to be provided with a property file containing
view names and view classes the resolver can use:

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
		<property name="basename" value="views"/>
	</bean>
----

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	...
	welcomeView.(class)=org.springframework.web.servlet.view.tiles3.TilesView
	welcomeView.url=welcome (this is the name of a Tiles definition)

	vetsView.(class)=org.springframework.web.servlet.view.tiles3.TilesView
	vetsView.url=vetsView (again, this is the name of a Tiles definition)

	findOwnersForm.(class)=org.springframework.web.servlet.view.JstlView
	findOwnersForm.url=/WEB-INF/jsp/findOwners.jsp
	...
----

As you can see, when using the `ResourceBundleViewResolver`, you can easily mix
different view technologies.

Note that the `TilesView` class supports JSTL (the JSP Standard Tag Library) out of the
box.


[[mvc-view-tiles-preparer]]
==== SimpleSpringPreparerFactory and SpringBeanPreparerFactory

As an advanced feature, Spring also supports two special Tiles `PreparerFactory`
implementations. Check out the Tiles documentation for details on how to use
`ViewPreparer` references in your Tiles definition files.

Specify `SimpleSpringPreparerFactory` to autowire ViewPreparer instances based on
specified preparer classes, applying Spring's container callbacks as well as applying
configured Spring BeanPostProcessors. If Spring's context-wide annotation-config has
been activated, annotations in ViewPreparer classes will be automatically detected and
applied. Note that this expects preparer __classes__ in the Tiles definition files, just
like the default `PreparerFactory` does.

Specify `SpringBeanPreparerFactory` to operate on specified preparer __names__ instead
of classes, obtaining the corresponding Spring bean from the DispatcherServlet's
application context. The full bean creation process will be in the control of the Spring
application context in this case, allowing for the use of explicit dependency injection
configuration, scoped beans etc. Note that you need to define one Spring bean definition
per preparer name (as used in your Tiles definitions).

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
		<property name="definitions">
			<list>
				<value>/WEB-INF/defs/general.xml</value>
				<value>/WEB-INF/defs/widgets.xml</value>
				<value>/WEB-INF/defs/administrator.xml</value>
				<value>/WEB-INF/defs/customer.xml</value>
				<value>/WEB-INF/defs/templates.xml</value>
			</list>
		</property>

		<!-- resolving preparer names as Spring bean definition names -->
		<property name="preparerFactoryClass"
				value="org.springframework.web.servlet.view.tiles3.SpringBeanPreparerFactory"/>

	</bean>
----




[[mvc-view-feeds]]
== RSS, Atom

Both `AbstractAtomFeedView` and `AbstractRssFeedView` inherit from the base class
`AbstractFeedView` and are used to provide Atom and RSS Feed views respectfully. They
are based on java.net's https://rome.dev.java.net[ROME] project and are located in the
package `org.springframework.web.servlet.view.feed`.

`AbstractAtomFeedView` requires you to implement the `buildFeedEntries()` method and
optionally override the `buildFeedMetadata()` method (the default implementation is
empty), as shown below.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	public class SampleContentAtomView extends AbstractAtomFeedView {

		@Override
		protected void buildFeedMetadata(Map<String, Object> model,
				Feed feed, HttpServletRequest request) {
			// implementation omitted
		}

		@Override
		protected List<Entry> buildFeedEntries(Map<String, Object> model,
				HttpServletRequest request, HttpServletResponse response) throws Exception {
			// implementation omitted
		}

	}
----

Similar requirements apply for implementing `AbstractRssFeedView`, as shown below.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	public class SampleContentAtomView extends AbstractRssFeedView {

		@Override
		protected void buildFeedMetadata(Map<String, Object> model,
				Channel feed, HttpServletRequest request) {
			// implementation omitted
		}

		@Override
		protected List<Item> buildFeedItems(Map<String, Object> model,
				HttpServletRequest request, HttpServletResponse response) throws Exception {
			// implementation omitted
		}

	}
----

The `buildFeedItems()` and `buildFeedEntires()` methods pass in the HTTP request in case
you need to access the Locale. The HTTP response is passed in only for the setting of
cookies or other HTTP headers. The feed will automatically be written to the response
object after the method returns.

For an example of creating an Atom view please refer to Alef Arendsen's Spring Team Blog
https://spring.io/blog/2009/03/16/adding-an-atom-view-to-an-application-using-spring-s-rest-support[entry].




[[mvc-view-document]]
== PDF, Excel



[[mvc-view-document-intro]]
=== Introduction

Returning an HTML page isn't always the best way for the user to view the model output,
and Spring makes it simple to generate a PDF document or an Excel spreadsheet
dynamically from the model data. The document is the view and will be streamed from the
server with the correct content type to (hopefully) enable the client PC to run their
spreadsheet or PDF viewer application in response.

In order to use Excel views, you need to add the Apache POI library to your classpath,
and for PDF generation preferably the OpenPDF library.

[NOTE]
====
Use the latest versions of the underlying document generation libraries if possible.
In particular, we strongly recommend OpenPDF (e.g. OpenPDF 1.0.5) instead of the
outdated original iText 2.1.7 since it is actively maintained and fixes an important
vulnerability for untrusted PDF content.
====



[[mvc-view-document-config]]
=== Configuration

Document based views are handled in an almost identical fashion to XSLT views, and the
following sections build upon the previous one by demonstrating how the same controller
used in the XSLT example is invoked to render the same model as both a PDF document and
an Excel spreadsheet (which can also be viewed or manipulated in Open Office).



[[mvc-view-document-configviews]]
=== View definition

First, let's amend the views.properties file (or xml equivalent) and add a simple view
definition for both document types. The entire file now looks like this with the XSLT
view shown from earlier:

[literal]
[subs="verbatim,quotes"]
----
home.(class)=xslt.HomePage
home.stylesheetLocation=/WEB-INF/xsl/home.xslt
home.root=words

xl.(class)=excel.HomePage

pdf.(class)=pdf.HomePage
----

__If you want to start with a template spreadsheet or a fillable PDF form to add your
model data to, specify the location as the 'url' property in the view definition__



[[mvc-view-document-configcontroller]]
=== Controller

The controller code we'll use remains exactly the same from the XSLT example earlier
other than to change the name of the view to use. Of course, you could be clever and
have this selected based on a URL parameter or some other logic - proof that Spring
really is very good at decoupling the views from the controllers!



[[mvc-view-document-configsubclasses]]
=== Excel views

Exactly as we did for the XSLT example, we'll subclass suitable abstract classes in
order to implement custom behavior in generating our output documents. For Excel, this
involves writing a subclass of
`org.springframework.web.servlet.view.document.AbstractExcelView` (for Excel files
generated by POI) or `org.springframework.web.servlet.view.document.AbstractJExcelView`
(for JExcelApi-generated Excel files) and implementing the `buildExcelDocument()` method.

Here's the complete listing for our POI Excel view which displays the word list from the
model map in consecutive rows of the first column of a new spreadsheet:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	package excel;

	// imports omitted for brevity

	public class HomePage extends AbstractExcelView {

		protected void buildExcelDocument(Map model, HSSFWorkbook wb, HttpServletRequest req,
				HttpServletResponse resp) throws Exception {

			HSSFSheet sheet;
			HSSFRow sheetRow;
			HSSFCell cell;

			// Go to the first sheet
			// getSheetAt: only if wb is created from an existing document
			// sheet = wb.getSheetAt(0);
			sheet = wb.createSheet("Spring");
			sheet.setDefaultColumnWidth((short) 12);

			// write a text at A1
			cell = getCell(sheet, 0, 0);
			setText(cell, "Spring-Excel test");

			List words = (List) model.get("wordList");
			for (int i=0; i < words.size(); i++) {
				cell = getCell(sheet, 2+i, 0);
				setText(cell, (String) words.get(i));
			}
		}

	}
----

And the following is a view generating the same Excel file, now using JExcelApi:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	package excel;

	// imports omitted for brevity

	public class HomePage extends AbstractJExcelView {

		protected void buildExcelDocument(Map model, WritableWorkbook wb,
				HttpServletRequest request, HttpServletResponse response) throws Exception {

			WritableSheet sheet = wb.createSheet("Spring", 0);

			sheet.addCell(new Label(0, 0, "Spring-Excel test"));

			List words = (List) model.get("wordList");
			for (int i = 0; i < words.size(); i++) {
				sheet.addCell(new Label(2+i, 0, (String) words.get(i)));
			}
		}
	}
----

Note the differences between the APIs. We've found that the JExcelApi is somewhat more
intuitive, and furthermore, JExcelApi has slightly better image-handling capabilities.
There have been memory problems with large Excel files when using JExcelApi however.

If you now amend the controller such that it returns `xl` as the name of the view (
`return new ModelAndView("xl", map);`) and run your application again, you should find
that the Excel spreadsheet is created and downloaded automatically when you request the
same page as before.



[[mvc-view-document-configsubclasspdf]]
=== PDF views

The PDF version of the word list is even simpler. This time, the class extends
`org.springframework.web.servlet.view.document.AbstractPdfView` and implements the
`buildPdfDocument()` method as follows:

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	package pdf;

	// imports omitted for brevity

	public class PDFPage extends AbstractPdfView {

		protected void buildPdfDocument(Map model, Document doc, PdfWriter writer,
			HttpServletRequest req, HttpServletResponse resp) throws Exception {
			List words = (List) model.get("wordList");
			for (int i=0; i<words.size(); i++) {
				doc.add( new Paragraph((String) words.get(i)));
			}
		}

	}
----

Once again, amend the controller to return the `pdf` view with `return new
ModelAndView("pdf", map);`, and reload the URL in your application. This time a PDF
document should appear listing each of the words in the model map.




[[mvc-view-jackson]]
== Jackson
[.small]#<<web-reactive.adoc#webflux-view-httpmessagewriter,Same in Spring WebFlux>>#



[[mvc-view-json-mapping]]
=== JSON
[.small]#<<web-reactive.adoc#webflux-view-httpmessagewriter,Same in Spring WebFlux>>#

The `MappingJackson2JsonView` uses the Jackson library's `ObjectMapper` to render the response
content as JSON. By default, the entire contents of the model map (with the exception of
framework-specific classes) will be encoded as JSON. For cases where the contents of the
map need to be filtered, users may specify a specific set of model attributes to encode
via the `RenderedAttributes` property. The `extractValueFromSingleKeyModel` property may
also be used to have the value in single-key models extracted and serialized directly
rather than as a map of model attributes.

JSON mapping can be customized as needed through the use of Jackson's provided
annotations. When further control is needed, a custom `ObjectMapper` can be injected
through the `ObjectMapper` property for cases where custom JSON
serializers/deserializers need to be provided for specific types.

As of Spring Framework 5.0.7, http://en.wikipedia.org/wiki/JSONP[JSONP] support is
deprecated and requires to customize the JSONP query parameter
name(s) through the `jsonpParameterNames` property. This support will be removed as of
Spring Framework 5.1, <<mvc-cors,CORS>> should be used instead.



[[mvc-view-xml-mapping]]
=== XML
[.small]#<<web-reactive.adoc#webflux-view-httpmessagewriter,Same in Spring WebFlux>>#

The `MappingJackson2XmlView` uses the
https://github.com/FasterXML/jackson-dataformat-xml[Jackson XML extension]'s `XmlMapper`
to render the response content as XML. If the model contains multiples entries, the
object to be serialized should be set explicitly using the `modelKey` bean property.
If the model contains a single entry, it will be serialized automatically.

XML mapping can be customized as needed through the use of JAXB or Jackson's provided
annotations. When further control is needed, a custom `XmlMapper` can be injected
through the `ObjectMapper` property for cases where custom XML
serializers/deserializers need to be provided for specific types.




[[mvc-view-xml-marshalling]]
== XML

The `MarshallingView` uses an XML `Marshaller` defined in the `org.springframework.oxm`
package to render the response content as XML. The object to be marshalled can be set
explicitly using ``MarhsallingView``'s `modelKey` bean property. Alternatively, the view
will iterate over all model properties and marshal the first type that is supported
by the `Marshaller`. For more information on the functionality in the
`org.springframework.oxm` package refer to the chapter <<oxm,Marshalling XML using O/X
Mappers>>.




[[mvc-view-xslt]]
== XSLT

XSLT is a transformation language for XML and is popular as a view technology within web
applications. XSLT can be a good choice as a view technology if your application
naturally deals with XML, or if your model can easily be converted to XML. The following
section shows how to produce an XML document as model data and have it transformed with
XSLT in a Spring Web MVC application.

This example is a trivial Spring application that creates a list of words in the
`Controller` and adds them to the model map. The map is returned along with the view
name of our XSLT view. See <<mvc-controller>> for details of Spring Web MVC's
`Controller` interface. The XSLT Controller will turn the list of words into a simple XML
document ready for transformation.



[[mvc-view-xslt-beandefs]]
=== Beans

Configuration is standard for a simple Spring application.
The MVC configuration has to define a `XsltViewResolver` bean and
regular MVC annotation configuration.

[source,java,indent=0]
[subs="verbatim,quotes"]
----
@EnableWebMvc
@ComponentScan
@Configuration
public class WebConfig implements WebMvcConfigurer {

	@Bean
	public XsltViewResolver xsltViewResolver() {
		XsltViewResolver viewResolver = new XsltViewResolver();
		viewResolver.setPrefix("/WEB-INF/xsl/");
		viewResolver.setSuffix(".xslt");
		return viewResolver;
	}

}
----

And we need a Controller that encapsulates our word generation logic.



[[mvc-view-xslt-controllercode]]
=== Controller

The controller logic is encapsulated in a `@Controller` class, with the
handler method being defined like so...

[source,java,indent=0]
[subs="verbatim,quotes"]
----
	@Controller
	public class XsltController {

		@RequestMapping("/")
		public String home(Model model) throws Exception {

			Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
			Element root = document.createElement("wordList");

			List<String> words = Arrays.asList("Hello", "Spring", "Framework");
			for (String word : words) {
				Element wordNode = document.createElement("word");
				Text textNode = document.createTextNode(word);
				wordNode.appendChild(textNode);
				root.appendChild(wordNode);
			}

			model.addAttribute("wordList", root);
			return "home";
		}

	}
----

So far we've only created a DOM document and added it to the Model map. Note that you
can also load an XML file as a `Resource` and use it instead of a custom DOM document.

Of course, there are software packages available that will automatically 'domify'
an object graph, but within Spring, you have complete flexibility to create the DOM
from your model in any way you choose. This prevents the transformation of XML playing
too great a part in the structure of your model data which is a danger when using tools
to manage the domification process.

Next, `XsltViewResolver` will resolve the "home" XSLT template file and merge the
DOM document into it to generate our view.



[[mvc-view-xslt-transforming]]
=== Transformation

Finally, the `XsltViewResolver` will resolve the "home" XSLT template file and merge the
DOM document into it to generate our view. As shown in the `XsltViewResolver`
configuration, XSLT templates live in the war file in the `'WEB-INF/xsl'` directory
and end with a `"xslt"` file extension.

[source,xml,indent=0]
[subs="verbatim,quotes"]
----
	<?xml version="1.0" encoding="utf-8"?>
	<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

		<xsl:output method="html" omit-xml-declaration="yes"/>

		<xsl:template match="/">
			<html>
				<head><title>Hello!</title></head>
				<body>
					<h1>My First Words</h1>
					<ul>
						<xsl:apply-templates/>
					</ul>
				</body>
			</html>
		</xsl:template>

		<xsl:template match="word">
			<li><xsl:value-of select="."/></li>
		</xsl:template>

	</xsl:stylesheet>
----

This is rendered as:

[source,html,indent=0]
[subs="verbatim,quotes"]
----
<html>
	<head>
		<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
		<title>Hello!</title>
	</head>
	<body>
		<h1>My First Words</h1>
		<ul>
			<li>Hello</li>
			<li>Spring</li>
			<li>Framework</li>
		</ul>
	</body>
</html>
----