Allow binding=false on @ModelAttribute

Issue: SPR-13402

spring-web/src/main/java/org/springframework/web/bind/annotation/ModelAttribute.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -22,6 +22,7 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.core.annotation.AliasFor;
 import org.springframework.ui.Model;
 
 /**
@@ -49,6 +50,7 @@ import org.springframework.ui.Model;
  * access to a {@link Model} argument.
  *
  * @author Juergen Hoeller
+ * @author Rossen Stoyanchev
  * @since 2.5
  */
 @Target({ElementType.PARAMETER, ElementType.METHOD})
@@ -56,6 +58,12 @@ import org.springframework.ui.Model;
 @Documented
 public @interface ModelAttribute {
 
+	/**
+	 * Alias for {@link #name}.
+	 */
+	@AliasFor("name")
+	String value() default "";
+
 	/**
 	 * The name of the model attribute to bind to.
 	 * <p>The default model attribute name is inferred from the declared
@@ -63,7 +71,19 @@ public @interface ModelAttribute {
 	 * based on the non-qualified class name:
 	 * e.g. "orderAddress" for class "mypackage.OrderAddress",
 	 * or "orderAddressList" for "List&lt;mypackage.OrderAddress&gt;".
+	 * @since 4.3
 	 */
-	String value() default "";
+	@AliasFor("value")
+	String name() default "";
+
+	/**
+	 * Allows declaring data binding disabled directly on an
+	 * {@code @ModelAttribute} method parameter or on the attribute returned from
+	 * an {@code @ModelAttribute} method, both of which would prevent data
+	 * binding for that attribute.
+	 * <p>By default this is set to "true" in which case data binding applies.
+	 * Set this to "false" to disable data binding.
+	 */
+	boolean binding() default true;
 
 }

spring-web/src/main/java/org/springframework/web/method/annotation/ModelAttributeMethodProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -101,9 +101,18 @@ public class ModelAttributeMethodProcessor
 		Object attribute = (mavContainer.containsAttribute(name) ? mavContainer.getModel().get(name) :
 				createAttribute(name, parameter, binderFactory, webRequest));
 
+		if (!mavContainer.isBindingDisabled(name)) {
+			ModelAttribute annotation = parameter.getParameterAnnotation(ModelAttribute.class);
+			if (annotation != null && !annotation.binding()) {
+				mavContainer.setBindingDisabled(name);
+			}
+		}
+
 		WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
 		if (binder.getTarget() != null) {
-			bindRequestParameters(binder, webRequest);
+			if (!mavContainer.isBindingDisabled(name)) {
+				bindRequestParameters(binder, webRequest);
+			}
 			validateIfApplicable(binder, parameter);
 			if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
 				throw new BindException(binder.getBindingResult());

spring-web/src/main/java/org/springframework/web/method/annotation/ModelFactory.java

@@ -132,9 +132,11 @@ public final class ModelFactory {
 
 		while (!this.modelMethods.isEmpty()) {
 			InvocableHandlerMethod modelMethod = getNextModelMethod(container).getHandlerMethod();
-			ModelAttribute annot = modelMethod.getMethodAnnotation(ModelAttribute.class);
-			String modelName = annot.value();
-			if (container.containsAttribute(modelName)) {
+			ModelAttribute annotation = modelMethod.getMethodAnnotation(ModelAttribute.class);
+			if (container.containsAttribute(annotation.name())) {
+				if (!annotation.binding()) {
+					container.setBindingDisabled(annotation.name());
+				}
 				continue;
 			}
 
@@ -142,6 +144,9 @@ public final class ModelFactory {
 
 			if (!modelMethod.isVoid()){
 				String returnValueName = getNameForReturnValue(returnValue, modelMethod.getReturnType());
+				if (!annotation.binding()) {
+					container.setBindingDisabled(returnValueName);
+				}
 				if (!container.containsAttribute(returnValueName)) {
 					container.addAttribute(returnValueName, returnValue);
 				}

spring-web/src/main/java/org/springframework/web/method/support/ModelAndViewContainer.java

@@ -16,7 +16,9 @@
 
 package org.springframework.web.method.support;
 
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.ui.Model;
@@ -55,6 +57,9 @@ public class ModelAndViewContainer {
 
 	private boolean redirectModelScenario = false;
 
+	/* Names of attributes with binding disabled */
+	private final Set<String> bindingDisabledAttributes = new HashSet<String>(4);
+
 	private HttpStatus status;
 
 	private final SessionStatus sessionStatus = new SimpleSessionStatus();
@@ -133,6 +138,23 @@ public class ModelAndViewContainer {
 		}
 	}
 
+	/**
+	 * Register an attribute for which data binding should not occur, for example
+	 * corresponding to an {@code @ModelAttribute(binding=false)} declaration.
+	 * @param attributeName the name of the attribute
+	 * @since 4.3
+	 */
+	public void setBindingDisabled(String attributeName) {
+		this.bindingDisabledAttributes.add(attributeName);
+	}
+
+	/**
+	 * Whether binding is disabled for the given model attribute.
+	 */
+	public boolean isBindingDisabled(String name) {
+		return this.bindingDisabledAttributes.contains(name);
+	}
+
 	/**
 	 * Whether to use the default model or the redirect model.
 	 */