POLISH CREATION OF DATA BINDERS FOR @RequestMapping METHODS

Make it possible to hook in custom ServletRequestDataBinderFactory
by overriding RequestMappingHandlerAdapter. 

Create ExtendedServletRequestDataBinder to add URI template vars
to the binding values taking advantage of a new extension hook in
ServletRequestDataBinder to provide additional values to bind.

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExtendedServletRequestDataBinder.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2002-2011 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.servlet.mvc.method.annotation;
+
+import java.util.Map;
+
+import javax.servlet.ServletRequest;
+
+import org.springframework.beans.MutablePropertyValues;
+import org.springframework.web.bind.ServletRequestDataBinder;
+import org.springframework.web.servlet.HandlerMapping;
+
+/**
+ * Subclass of {@link ServletRequestDataBinder} that adds URI template variables
+ * to the values used for data binding.
+ *
+ * @author Rossen Stoyanchev
+ * @since 3.1
+ */
+public class ExtendedServletRequestDataBinder extends ServletRequestDataBinder {
+
+	/**
+	 * Create a new instance, with default object name.
+	 * @param target the target object to bind onto (or <code>null</code>
+	 * if the binder is just used to convert a plain parameter value)
+	 * @see #DEFAULT_OBJECT_NAME
+	 */
+	public ExtendedServletRequestDataBinder(Object target) {
+		super(target);
+	}
+
+	/**
+	 * Create a new instance.
+	 * @param target the target object to bind onto (or <code>null</code>
+	 * if the binder is just used to convert a plain parameter value)
+	 * @param objectName the name of the target object
+	 * @see #DEFAULT_OBJECT_NAME
+	 */
+	public ExtendedServletRequestDataBinder(Object target, String objectName) {
+		super(target, objectName);
+	}
+
+	/**
+	 * Add URI template variables to the property values used for data binding.
+	 */
+	@Override 
+	@SuppressWarnings("unchecked")
+	protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
+		String attr = HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE;
+		mpvs.addPropertyValues((Map<String, String>) request.getAttribute(attr));
+	}	
+
+}

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerAdapter.java

@@ -676,7 +676,7 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter i
 		return modelFactory;
 	}
 
-	private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) {
+	private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) throws Exception {
 		Class<?> handlerType = handlerMethod.getBeanType();
 		WebDataBinderFactory binderFactory = this.dataBinderFactoryCache.get(handlerType);
 		if (binderFactory == null) {
@@ -688,12 +688,25 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter i
 				binderMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
 				binderMethods.add(binderMethod);
 			}
-			binderFactory = new ServletRequestDataBinderFactory(binderMethods, this.webBindingInitializer);
+			binderFactory = createDataBinderFactory(binderMethods);
 			this.dataBinderFactoryCache.put(handlerType, binderFactory);
 		}
 		return binderFactory;
 	}
 
+	/**
+	 * Template method to create a new ServletRequestDataBinderFactory instance.
+	 * <p>The default implementation creates a ServletRequestDataBinderFactory.
+	 * This can be overridden for custom ServletRequestDataBinder subclasses.
+	 * @param binderMethods {@code @InitBinder} methods
+	 * @return the ServletRequestDataBinderFactory instance to use
+	 * @throws Exception in case of invalid state or arguments
+	 */
+	protected ServletRequestDataBinderFactory createDataBinderFactory(List<InvocableHandlerMethod> binderMethods)
+			throws Exception {
+		return new ServletRequestDataBinderFactory(binderMethods, getWebBindingInitializer());
+	}
+
 	/**
 	 * MethodFilter that matches {@link InitBinder @InitBinder} methods.
 	 */

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ServletRequestDataBinderFactory.java

@@ -17,21 +17,15 @@
 package org.springframework.web.servlet.mvc.method.annotation;
 
 import java.util.List;
-import java.util.Map;
 
-import org.springframework.beans.MutablePropertyValues;
 import org.springframework.web.bind.ServletRequestDataBinder;
-import org.springframework.web.bind.WebDataBinder;
 import org.springframework.web.bind.support.WebBindingInitializer;
 import org.springframework.web.context.request.NativeWebRequest;
-import org.springframework.web.context.request.RequestAttributes;
 import org.springframework.web.method.annotation.InitBinderDataBinderFactory;
 import org.springframework.web.method.support.InvocableHandlerMethod;
-import org.springframework.web.servlet.HandlerMapping;
 
 /**
- * Creates a WebDataBinder of type {@link ServletRequestDataBinder} that can 
- * also use URI template variables values for data binding purposes.
+ * Creates a {@code ServletRequestDataBinder}.
  *
  * @author Rossen Stoyanchev
  * @since 3.1
@@ -43,45 +37,16 @@ public class ServletRequestDataBinderFactory extends InitBinderDataBinderFactory
 	 * @param binderMethods one or more {@code @InitBinder} methods
 	 * @param initializer provides global data binder initialization
 	 */
-	public ServletRequestDataBinderFactory(List<InvocableHandlerMethod> binderMethods, 
-										   WebBindingInitializer initializer) {
+	public ServletRequestDataBinderFactory(List<InvocableHandlerMethod> binderMethods, WebBindingInitializer initializer) {
 		super(binderMethods, initializer);
 	}
-	
-	/**
-	 * Create a WebDataBinder of type {@link ServletRequestDataBinder} that can 
-	 * also use URI template variables values for data binding purposes.
-	 */
-	@Override
-	protected WebDataBinder createBinderInstance(Object target, String objectName, final NativeWebRequest request) {
-		return new ServletRequestDataBinder(target, objectName) {
-			@Override
-			protected void doBind(MutablePropertyValues mpvs) {
-				mergeUriTemplateVariables(mpvs, request);
-				super.doBind(mpvs);
-			}
-		};
-	}
 
 	/**
-	 * Merge URI variable values into the given PropertyValues.
-	 * @param mpvs the PropertyValues to add to
-	 * @param request the current request
+	 * Returns an instance of {@link ExtendedServletRequestDataBinder}.
 	 */
-	@SuppressWarnings("unchecked")
-	protected final void mergeUriTemplateVariables(MutablePropertyValues mpvs, NativeWebRequest request) {
-
-		Map<String, String> uriTemplateVars = 
-			(Map<String, String>) request.getAttribute(
-					HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);
-		
-		if (uriTemplateVars != null){
-			for (String variableName : uriTemplateVars.keySet()) {
-				if (!mpvs.contains(variableName)) {
-					mpvs.addPropertyValue(variableName, uriTemplateVars.get(variableName));
-				}
-			}
-		}
+	@Override
+	protected ServletRequestDataBinder createBinderInstance(Object target, String objectName, NativeWebRequest request) {
+		return new ExtendedServletRequestDataBinder(target, objectName);
 	}
 
 }

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ExtendedServletRequestDataBinderTests.java

@@ -21,42 +21,26 @@ import static org.junit.Assert.assertEquals;
 import java.util.HashMap;
 import java.util.Map;
 
-import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.springframework.beans.TestBean;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.web.bind.ServletRequestDataBinder;
 import org.springframework.web.bind.WebDataBinder;
-import org.springframework.web.context.request.NativeWebRequest;
-import org.springframework.web.context.request.RequestContextHolder;
-import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.servlet.HandlerMapping;
 
 /**
- * Test fixture with {@link ServletRequestDataBinderFactory}.
+ * Test fixture for {@link ExtendedServletRequestDataBinder}.
  *
  * @author Rossen Stoyanchev
  */
-public class ServletRequestDataBinderFactoryTests {
+public class ExtendedServletRequestDataBinderTests {
 
-	private ServletRequestDataBinderFactory binderFactory;
-	
 	private MockHttpServletRequest request;
 	
-	private NativeWebRequest webRequest;
-
 	@Before
 	public void setup() {
-		binderFactory = new ServletRequestDataBinderFactory(null, null);
-		request = new MockHttpServletRequest();
-		webRequest = new ServletWebRequest(request);
-		RequestContextHolder.setRequestAttributes(webRequest);
-	}
-	
-	@After
-	public void teardown() {
-		RequestContextHolder.resetRequestAttributes();
+		this.request = new MockHttpServletRequest();
 	}
 	
 	@Test
@@ -67,7 +51,7 @@ public class ServletRequestDataBinderFactoryTests {
 		request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, uriTemplateVars);
 		
 		TestBean target = new TestBean();
-		WebDataBinder binder = binderFactory.createBinder(webRequest, target, "");
+		WebDataBinder binder = new ExtendedServletRequestDataBinder(target, "");
 		((ServletRequestDataBinder) binder).bind(request);
 
 		assertEquals("nameValue", target.getName());
@@ -75,7 +59,7 @@ public class ServletRequestDataBinderFactoryTests {
 	}
 
 	@Test
-	public void requestParamsOverrideUriTemplateVars() throws Exception {
+	public void uriTemplateVarAndRequestParam() throws Exception {
 		request.addParameter("age", "35");
 		
 		Map<String, String> uriTemplateVars = new HashMap<String, String>();
@@ -84,17 +68,17 @@ public class ServletRequestDataBinderFactoryTests {
 		request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, uriTemplateVars);
 		
 		TestBean target = new TestBean();
-		WebDataBinder binder = binderFactory.createBinder(webRequest, target, "");
+		WebDataBinder binder = new ExtendedServletRequestDataBinder(target, "");
 		((ServletRequestDataBinder) binder).bind(request);
 
 		assertEquals("nameValue", target.getName());
-		assertEquals(35, target.getAge());
+		assertEquals(25, target.getAge());
 	}
 
 	@Test
 	public void noUriTemplateVars() throws Exception {
 		TestBean target = new TestBean();
-		WebDataBinder binder = binderFactory.createBinder(webRequest, target, "");
+		WebDataBinder binder = new ExtendedServletRequestDataBinder(target, "");
 		((ServletRequestDataBinder) binder).bind(request);
 
 		assertEquals(null, target.getName());

org.springframework.web/src/main/java/org/springframework/web/bind/ServletRequestDataBinder.java

@@ -108,9 +108,20 @@ public class ServletRequestDataBinder extends WebDataBinder {
 		if (multipartRequest != null) {
 			bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
 		}
+		addBindValues(mpvs, request);
 		doBind(mpvs);
 	}
 
+	/**
+	 * Extension point that subclasses can use to add extra bind values for a
+	 * request. Invoked before {@link #doBind(MutablePropertyValues)}.
+	 * The default implementation is empty. 
+	 * @param mpvs the property values that will be used for data binding
+	 * @param request the current request
+	 */
+	protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
+	}
+
 	/**
 	 * Treats errors as fatal.
 	 * <p>Use this method only if it's an error if the input isn't valid.

org.springframework.web/src/main/java/org/springframework/web/bind/support/DefaultDataBinderFactory.java

@@ -41,10 +41,12 @@ public class DefaultDataBinderFactory implements WebDataBinderFactory {
 	/**
 	 * Create a new {@link WebDataBinder} for the given target object and 
 	 * initialize it through a {@link WebBindingInitializer}. 
+	 * @throws Exception in case of invalid state or arguments
 	 */
-	public final WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName) throws Exception {
+	public final WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName)
+			throws Exception {
 		WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest);
-		if (initializer != null) {
+		if (this.initializer != null) {
 			this.initializer.initBinder(dataBinder, webRequest);
 		}
 		initBinder(dataBinder, webRequest);
@@ -52,13 +54,15 @@ public class DefaultDataBinderFactory implements WebDataBinderFactory {
 	}
 
 	/**
-	 * Extension point to create the WebDataBinder instance, which is
-	 * {@link WebRequestDataBinder} by default.
+	 * Extension point to create the WebDataBinder instance.
+	 * By default this is {@code WebRequestDataBinder}.
 	 * @param target the binding target or {@code null} for type conversion only
 	 * @param objectName the binding target object name 
 	 * @param webRequest the current request
+	 * @throws Exception in case of invalid state or arguments
 	 */
-	protected WebDataBinder createBinderInstance(Object target, String objectName, NativeWebRequest webRequest) {
+	protected WebDataBinder createBinderInstance(Object target, String objectName, NativeWebRequest webRequest)
+			throws Exception {
 		return new WebRequestDataBinder(target, objectName);
 	}
 

org.springframework.web/src/main/java/org/springframework/web/method/annotation/InitBinderDataBinderFactory.java

@@ -58,12 +58,11 @@ public class InitBinderDataBinderFactory extends DefaultDataBinderFactory {
 	@Override
 	public void initBinder(WebDataBinder binder, NativeWebRequest request) throws Exception {
 		for (InvocableHandlerMethod binderMethod : this.binderMethods) {
-			if (!invokeInitBinderMethod(binderMethod, binder)) {
-				continue;
-			}
-			Object returnValue = binderMethod.invokeForRequest(request, null, binder);
-			if (returnValue != null) {
-				throw new IllegalStateException("@InitBinder methods should return void: " + binderMethod);
+			if (isBinderMethodApplicable(binderMethod, binder)) {
+				Object returnValue = binderMethod.invokeForRequest(request, null, binder);
+				if (returnValue != null) {
+					throw new IllegalStateException("@InitBinder methods should return void: " + binderMethod);
+				}
 			}
 		}
 	}
@@ -74,8 +73,8 @@ public class InitBinderDataBinderFactory extends DefaultDataBinderFactory {
 	 * <p>The default implementation checks if target object name is included
 	 * in the attribute names specified in the {@code @InitBinder} annotation.
 	 */
-	protected boolean invokeInitBinderMethod(HandlerMethod binderMethod, WebDataBinder binder) {
-		InitBinder annot = binderMethod.getMethodAnnotation(InitBinder.class);
+	protected boolean isBinderMethodApplicable(HandlerMethod initBinderMethod, WebDataBinder binder) {
+		InitBinder annot = initBinderMethod.getMethodAnnotation(InitBinder.class);
 		Collection<String> names = Arrays.asList(annot.value());
 		return (names.size() == 0 || names.contains(binder.getObjectName()));
 	}