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Moved REST Etag filter to MVC chapter 

git-svn-id: https://src.springframework.org/svn/spring-framework/trunk@1390 50f2f4bb-b051-0410-bef5-90022cba6387
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Arjen Poutsma 17 years ago
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  1. 365
      spring-framework-reference/src/mvc.xml

365
spring-framework-reference/src/mvc.xml
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@ -1295,8 +1295,8 @@ public void handle(@RequestBody String body, Writer writer) throws IOException {
</section> </section>
<section id="mvc-ann-responsebody"> <section id="mvc-ann-responsebody">
<title>Mapping the response body with the @ResponseBody <title>Mapping the response body with the @ResponseBody
annotation</title> annotation</title>
<para>Similar to <interfacename>@RequestBody</interfacename>, there is <para>Similar to <interfacename>@RequestBody</interfacename>, there is
the <interfacename>@ResponseBody</interfacename> annotation. This the <interfacename>@ResponseBody</interfacename> annotation. This
@ -1550,15 +1550,15 @@ public class MyFormController {
<section id="mvc-handlermapping"> <section id="mvc-handlermapping">
<title>Handler mappings</title> <title>Handler mappings</title>
<para>In previous versions of Spring MVC, users were required to define <interfacename>HandlerMapping</interfacename>s in <para>In previous versions of Spring MVC, users were required to define
the web application context <interfacename>HandlerMapping</interfacename>s in the web application
to map incoming web requests to context to map incoming web requests to appropriate handlers. With the
appropriate handlers. With the introduction of Spring 2.5, the <classname>DispatcherServlet</classname> enables the introduction of Spring 2.5, the <classname>DispatcherServlet</classname>
<classname>DefaultAnnotationHandlerMapping</classname>, which looks for enables the <classname>DefaultAnnotationHandlerMapping</classname>, which
<interfacename>@RequestMapping</interfacename> annotations on <interfacename>@Controllers</interfacename>. looks for <interfacename>@RequestMapping</interfacename> annotations on
Typically, you do not need to override this default mapping, except when overriding the properties. <interfacename>@Controllers</interfacename>. Typically, you do not need to
These properties are: override this default mapping, except when overriding the properties.
</para> These properties are:</para>
<itemizedlist spacing="compact"> <itemizedlist spacing="compact">
<listitem> <listitem>
@ -1615,16 +1615,17 @@ public class MyFormController {
subclasses of subclasses of
<classname>org.springframework.web.servlet.handler.AbstractUrlHandlerMapping</classname></emphasis>).</para> <classname>org.springframework.web.servlet.handler.AbstractUrlHandlerMapping</classname></emphasis>).</para>
<para>The following example shows how to override the default mapping, and add an interceptor:</para> <para>The following example shows how to override the default mapping, and
add an interceptor:</para>
<programlisting language="xml"><![CDATA[<beans> <programlisting language="xml">&lt;beans&gt;
<bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"> &lt;bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"&gt;
<property name="interceptors"> &lt;property name="interceptors"&gt;
<bean class="example.MyInterceptor"/> &lt;bean class="example.MyInterceptor"/&gt;
</property> &lt;/property&gt;
</bean> &lt;/bean&gt;
<beans>]]></programlisting> &lt;beans&gt;</programlisting>
<section id="mvc-handlermapping-interceptor"> <section id="mvc-handlermapping-interceptor">
<title>Intercepting requests - the <title>Intercepting requests - the
@ -1841,10 +1842,11 @@ public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
<row> <row>
<entry><classname>ContentNegotiatingViewResolver</classname></entry> <entry><classname>ContentNegotiatingViewResolver</classname></entry>
<entry>An implementation of the <interfacename>ViewResolver</interfacename> <entry>An implementation of the
interface that that resolves a view based on the request file name or <literal>Accept</literal> header. <interfacename>ViewResolver</interfacename> interface that that
See <xref linkend="mvc-multiple-representations"/>. resolves a view based on the request file name or
</entry> <literal>Accept</literal> header. See <xref
linkend="mvc-multiple-representations" />.</entry>
</row> </row>
</tbody> </tbody>
</tgroup> </tgroup>
@ -2068,139 +2070,138 @@ public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
</section> </section>
</section> </section>
<section id="mvc-multiple-representations"> <section id="mvc-multiple-representations">
<title><classname>ContentNegotiatingViewResolver</classname></title> <title><classname>ContentNegotiatingViewResolver</classname></title>
<para>The <classname>ContentNegotiatingViewResolver</classname> <para>The <classname>ContentNegotiatingViewResolver</classname> does not
does not resolve views itself, but rather delegates to other resolve views itself, but rather delegates to other view resolvers,
view resolvers, selecting the view that resembles the representation selecting the view that resembles the representation requested by the
requested by the client. client. There are two strategies for a client to inform the server of
There are two strategies for a client to inform the server of the representation it is interested in receiving.</para>
the representation it is interested in receiving.</para>
<para>The first strategy is to use a distinct URI for each resource.
<para>The first strategy is to use a distinct URI for each resource. This is typically done by using a different file extension in the URI.
This is typically done by using a different file extension in the URI. For example the URI<literal>
For example the URI<literal> http://www.example.com/users/fred.pdf</literal> requests a PDF
http://www.example.com/users/fred.pdf</literal> requests a PDF representation of the user fred while
representation of the user fred while <literal>http://www.example.com/users/fred.xml</literal> requests an XML
<literal>http://www.example.com/users/fred.xml</literal> requests an XML representation.</para>
representation.</para>
<para>The second strategy is for the client to use the same URI to
<para>The second strategy is for the client to use the same URI to locate the resource but set the <literal>Accept</literal> HTTP request
locate the resource but set the <literal>Accept</literal> HTTP request header to list the <ulink
header to list the <ulink url="http://en.wikipedia.org/wiki/Internet_media_type">media
url="http://en.wikipedia.org/wiki/Internet_media_type">media types</ulink> that it understands. For example, a HTTP request for
types</ulink> that it understands. For example, a HTTP request for <literal>http://www.example.com/users/fred</literal> with an
<literal>http://www.example.com/users/fred</literal> with an <literal>Accept</literal> header set to <literal>application/pdf
<literal>Accept</literal> header set to <literal>application/pdf </literal>requests a PDF representation of the user fred while
</literal>requests a PDF representation of the user fred while <literal>http://www.example.com/users/fred</literal> with an
<literal>http://www.example.com/users/fred</literal> with an <literal>Accept</literal> header set to <literal>text/xml</literal>
<literal>Accept</literal> header set to <literal>text/xml</literal> requests an XML representation. This strategy is known as <ulink
requests an XML representation. This strategy is known as <ulink url="http://en.wikipedia.org/wiki/Content_negotiation">content
url="http://en.wikipedia.org/wiki/Content_negotiation">content negotiation</ulink>.</para>
negotiation</ulink>.</para>
<note>
<note> <para>One issue with the Accept header is that is impossible to change
<para>One issue with the Accept header is that is impossible to change it in a web browser, in HTML. For instance, in Firefox, it's fixed
it in a web browser, in HTML. For instance, in Firefox, it's fixed to</para>
to</para>
<programlisting>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
<programlisting>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
</programlisting> </programlisting>
<para>For this reason it is common to see the use of a distinct URI <para>For this reason it is common to see the use of a distinct URI
for each representation.</para> for each representation.</para>
</note> </note>
<para>To support multiple representations of a resource Spring provides <para>To support multiple representations of a resource Spring provides
the <classname>ContentNegotiatingViewResolver</classname> to resolve a the <classname>ContentNegotiatingViewResolver</classname> to resolve a
view based on the file extension or <literal>Accept</literal> header of view based on the file extension or <literal>Accept</literal> header of
the HTTP request. <classname>ContentNegotiatingViewResolver</classname> the HTTP request. <classname>ContentNegotiatingViewResolver</classname>
does not perform the view resolution itself, but instead delegates to a does not perform the view resolution itself, but instead delegates to a
list of view resolvers set using the bean property list of view resolvers set using the bean property
<literal>ViewResolvers</literal>.</para> <literal>ViewResolvers</literal>.</para>
<para>The <classname>ContentNegotiatingViewResolver</classname> selects <para>The <classname>ContentNegotiatingViewResolver</classname> selects
an appropriate <classname>View</classname> to handle the request by an appropriate <classname>View</classname> to handle the request by
comparing the request media type(s) with the media type (a.k.a. comparing the request media type(s) with the media type (a.k.a.
<literal>Content-Type</literal>) supported by the <literal>Content-Type</literal>) supported by the
<classname>View</classname> associated with each of its <classname>View</classname> associated with each of its
<classname>ViewResolvers</classname>. The first <classname>ViewResolvers</classname>. The first
<classname>View</classname> in the list that has a compatible <classname>View</classname> in the list that has a compatible
<literal>Content-Type</literal> is used to return the representation to <literal>Content-Type</literal> is used to return the representation to
the client. The <literal>Accept</literal> header may include wild cards, the client. The <literal>Accept</literal> header may include wild cards,
for example 'text/*', in which case a <classname>View</classname> whose for example 'text/*', in which case a <classname>View</classname> whose
Context-Type was 'text/xml' is a compatible match.</para> Context-Type was 'text/xml' is a compatible match.</para>
<para>To support the resolution of a view based on a file extension, <para>To support the resolution of a view based on a file extension,
<classname>ContentNegotiatingViewResolver</classname>'s bean property <classname>ContentNegotiatingViewResolver</classname>'s bean property
<literal>MediaTypes</literal> is used to specify a mapping of file <literal>MediaTypes</literal> is used to specify a mapping of file
extensions to media types. For more information on the algorithm to extensions to media types. For more information on the algorithm to
determine the request media type, refer to the API documentation for determine the request media type, refer to the API documentation for
<classname>ContentNegotiatingViewResolver</classname>..</para> <classname>ContentNegotiatingViewResolver</classname>..</para>
<para>Here is an example configuration of a <para>Here is an example configuration of a
<classname>ContentNegotiatingViewResolver</classname></para> <classname>ContentNegotiatingViewResolver</classname></para>
<programlisting language="xml"><![CDATA[<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver"> <programlisting language="xml">&lt;bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver"&gt;
<property name="mediaTypes"> &lt;property name="mediaTypes"&gt;
<map> &lt;map&gt;
<entry key="atom" value="application/atom+xml"/> &lt;entry key="atom" value="application/atom+xml"/&gt;
<entry key="html" value="text/html"/> &lt;entry key="html" value="text/html"/&gt;
</map> &lt;/map&gt;
</property> &lt;/property&gt;
<property name="viewResolvers"> &lt;property name="viewResolvers"&gt;
<list> &lt;list&gt;
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/> &lt;bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/&gt;
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> &lt;bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"&gt;
<property name="prefix" value="/WEB-INF/jsp/"/> &lt;property name="prefix" value="/WEB-INF/jsp/"/&gt;
<property name="suffix" value=".jsp"/> &lt;property name="suffix" value=".jsp"/&gt;
</bean> &lt;/bean&gt;
</list> &lt;/list&gt;
</property> &lt;/property&gt;
</bean> &lt;/bean&gt;
<bean id="content" class="com.springsource.samples.rest.SampleContentAtomView"/>]]></programlisting> &lt;bean id="content" class="com.springsource.samples.rest.SampleContentAtomView"/&gt;</programlisting>
<para>The <classname>InternalResourceViewResolver</classname> handles <para>The <classname>InternalResourceViewResolver</classname> handles
the translation of view names and JSP pages while the the translation of view names and JSP pages while the
<classname>BeanNameViewResolver</classname> returns a view based on the <classname>BeanNameViewResolver</classname> returns a view based on the
name of a bean. (See "<link name of a bean. (See "<link
linkend="mvc-viewresolver-resolver">Resolving views - the ViewResolver linkend="mvc-viewresolver-resolver">Resolving views - the ViewResolver
interface</link>" for more details on how Spring looks up and interface</link>" for more details on how Spring looks up and
instantiates a view.) In this example, the <literal>content</literal> instantiates a view.) In this example, the <literal>content</literal>
bean is a class that inherits from bean is a class that inherits from
<classname>AbstractAtomFeedView</classname> which returns an Atom RSS <classname>AbstractAtomFeedView</classname> which returns an Atom RSS
feed. For more information on creating an Atom Feed representation see feed. For more information on creating an Atom Feed representation see
the section 'Atom Views'.</para> the section 'Atom Views'.</para>
<para>In this configuration, if a request is made with a .html extension <para>In this configuration, if a request is made with a .html extension
the view resolver will look for a view that matches the text/html media the view resolver will look for a view that matches the text/html media
type. The <classname>InternalResourceViewResolver</classname> provides type. The <classname>InternalResourceViewResolver</classname> provides
the matching view for text/html. If the request is made with the file the matching view for text/html. If the request is made with the file
extension .atom, the view resolver will look for a view that matches the extension .atom, the view resolver will look for a view that matches the
application/atom+xml media type. This view is provided by the application/atom+xml media type. This view is provided by the
<classname>BeanNameViewResolver</classname> that maps to the <classname>BeanNameViewResolver</classname> that maps to the
<classname>SampleContentAtomView</classname> if the view name returned <classname>SampleContentAtomView</classname> if the view name returned
is 'content'. Alternatively, client requests could be made without a is 'content'. Alternatively, client requests could be made without a
file extension and setting the Accept header to the preferred media-type file extension and setting the Accept header to the preferred media-type
and the same resolution of request to views would occur.</para> and the same resolution of request to views would occur.</para>
<note> <note>
<para>If <classname>ContentNegotiatingViewResolver</classname>'s list <para>If <classname>ContentNegotiatingViewResolver</classname>'s list
of ViewResolvers is not configured explicitly, then it will of ViewResolvers is not configured explicitly, then it will
automatically use any ViewResolvers defined in the application automatically use any ViewResolvers defined in the application
context.</para> context.</para>
</note> </note>
<para>The corresponding controller code that returns an Atom RSS feed <para>The corresponding controller code that returns an Atom RSS feed
for a URI of the form <literal>http://localhost/content.atom</literal> for a URI of the form <literal>http://localhost/content.atom</literal>
or <literal>http://localhost/content</literal> with an or <literal>http://localhost/content</literal> with an
<literal>Accept</literal> header of application/atom+xml is shown <literal>Accept</literal> header of application/atom+xml is shown
below</para> below</para>
<programlisting language="java">@Controller <programlisting language="java">@Controller
public class ContentController { public class ContentController {
private List&lt;SampleContent&gt; contentList = new ArrayList&lt;SampleContent&gt;(); private List&lt;SampleContent&gt; contentList = new ArrayList&lt;SampleContent&gt;();
@ -2214,9 +2215,7 @@ public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
} }
}</programlisting> }</programlisting>
</section>
</section>
</section> </section>
<section id="mvc-localeresolver"> <section id="mvc-localeresolver">
@ -2813,9 +2812,11 @@ public class FileUploadBean {
<section id="mvc-ann-exceptionhandler"> <section id="mvc-ann-exceptionhandler">
<title><interfacename>@ExceptionResolver</interfacename></title> <title><interfacename>@ExceptionResolver</interfacename></title>
<para>As an alternative to implementing the <interfacename>HandlerExceptionResolver</interfacename>, you <para>As an alternative to implementing the
can use the <interfacename>@ExceptionHandler</interfacename>. The <classname>@ExceptionHandler</classname> method annotation is <interfacename>HandlerExceptionResolver</interfacename>, you can use the
used within a controller to specify which method will be invoked when an <interfacename>@ExceptionHandler</interfacename>. The
<classname>@ExceptionHandler</classname> method annotation is used
within a controller to specify which method will be invoked when an
exception of a specific type is thrown during the execution of exception of a specific type is thrown during the execution of
controller methods. For example</para> controller methods. For example</para>
@ -2851,7 +2852,6 @@ public class SimpleController {
<classname>ModelAndView</classname> object. Please refer to the API <classname>ModelAndView</classname> object. Please refer to the API
documentation for more details.</para> documentation for more details.</para>
</section> </section>
</section> </section>
<section id="mvc-coc"> <section id="mvc-coc">
@ -3189,6 +3189,49 @@ public class SimpleController {
</section> </section>
</section> </section>
<section id="mvc-etag">
<title>ETag support</title>
<para>An <ulink url="http://en.wikipedia.org/wiki/HTTP_ETag">ETag</ulink>
(entity tag) is an HTTP response header returned by an HTTP/1.1 compliant
web server used to determine change in content at a given URL. It can be
considered to be the more sophisticated successor to the
<literal>Last-Modified</literal> header. When a server returns a
representation with an ETag header, the client can use this header in
subsequent GETs, in an <literal>If-None-Match</literal> header. If the
content has not changed, the server will return <literal>304: Not
Modified</literal>.</para>
<para>Support for ETags is provided by the servlet filter
<classname>ShallowEtagHeaderFilter</classname>. Since it is a plain
Servlet Filter, and thus can be used in combination with any web
framework. The <classname>ShallowEtagHeaderFilter</classname> filter
creates so-called shallow ETags (as opposed to deep ETags, more about that
later). The way it works is quite simple: the filter simply caches the
content of the rendered JSP (or other content), generates an MD5 hash over
that, and returns that as an ETag header in the response. The next time a
client sends a request for the same resource, it uses that hash as the
<literal>If-None-Match</literal> value. The filter notices this, renders
the view again, and compares the two hashes. If they are equal, a
<literal>304</literal> is returned. It is important to note that this
filter will not save processing power, as the view is still rendered. The
only thing it saves is bandwidth, as the rendered response is not sent
back over the wire.</para>
<para>You configure the <classname>ShallowEtagHeaderFilter</classname> in
<filename>web.xml</filename>:</para>
<programlisting language="xml">&lt;filter&gt;
&lt;filter-name&gt;etagFilter&lt;/filter-name&gt;
&lt;filter-class&gt;org.springframework.web.filter.ShallowEtagHeaderFilter&lt;/filter-class&gt;
&lt;/filter&gt;
&lt;filter-mapping&gt;
&lt;filter-name&gt;etagFilter&lt;/filter-name&gt;
&lt;servlet-name&gt;petclinic&lt;/servlet-name&gt;
&lt;/filter-mapping&gt;</programlisting>
</section>
<section id="mvc-resources"> <section id="mvc-resources">
<title>Further Resources</title> <title>Further Resources</title>

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