Allow to customize TestDispatcherServlet

This commit introduces the `DispatcherServletCustomizer` callback
interface that can be used to customize the `DispatcherServlet` that a
`MockMvc` is using.

Previously, only the `dispatchOptions` flag can be customized. This
commit allows to customize any property of `DispatcherServlet` before it
is initialized.

Issue: SPR-14277

spring-test/src/main/java/org/springframework/test/web/servlet/DispatcherServletCustomizer.java

@@ -0,0 +1,37 @@
+/*
+ * 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.
+ * 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.test.web.servlet;
+
+import org.springframework.web.servlet.DispatcherServlet;
+
+/**
+ * Strategy interface for customizing {@link DispatcherServlet} instances that are
+ * managed by {@link MockMvc}.
+ *
+ * @author Stephane Nicoll
+ * @since 4.3.4
+ */
+public interface DispatcherServletCustomizer {
+
+	/**
+	 * Customize the supplied {@link DispatcherServlet} <em>before</em> it is
+	 * initialized.
+	 * @param dispatcherServlet the dispatcher servlet to customize
+	 */
+	void customize(DispatcherServlet dispatcherServlet);
+
+}

spring-test/src/main/java/org/springframework/test/web/servlet/MockMvcBuilderSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -35,6 +35,7 @@ import org.springframework.web.context.WebApplicationContext;
  *
  * @author Rossen Stoyanchev
  * @author Rob Winch
+ * @author Stephane Nicoll
  * @since 3.2
  */
 public abstract class MockMvcBuilderSupport {
@@ -42,12 +43,16 @@ public abstract class MockMvcBuilderSupport {
 	protected final MockMvc createMockMvc(Filter[] filters, MockServletConfig servletConfig,
 			WebApplicationContext webAppContext, RequestBuilder defaultRequestBuilder,
 			List<ResultMatcher> globalResultMatchers, List<ResultHandler> globalResultHandlers,
-			Boolean dispatchOptions) {
+			List<DispatcherServletCustomizer> dispatcherServletCustomizers) {
 
 		ServletContext servletContext = webAppContext.getServletContext();
 
 		TestDispatcherServlet dispatcherServlet = new TestDispatcherServlet(webAppContext);
-		dispatcherServlet.setDispatchOptionsRequest(dispatchOptions);
+		if (dispatcherServletCustomizers != null) {
+			for (DispatcherServletCustomizer customizers : dispatcherServletCustomizers) {
+				customizers.customize(dispatcherServlet);
+			}
+		}
 		try {
 			dispatcherServlet.init(servletConfig);
 		}

spring-test/src/main/java/org/springframework/test/web/servlet/setup/AbstractMockMvcBuilder.java

@@ -22,6 +22,7 @@ import javax.servlet.Filter;
 import javax.servlet.ServletContext;
 
 import org.springframework.mock.web.MockServletConfig;
+import org.springframework.test.web.servlet.DispatcherServletCustomizer;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MockMvcBuilderSupport;
 import org.springframework.test.web.servlet.RequestBuilder;
@@ -42,6 +43,7 @@ import org.springframework.web.context.WebApplicationContext;
  * pass to the DispatcherServlet.
  *
  * @author Rossen Stoyanchev
+ * @author Stephane Nicoll
  * @since 4.0
  */
 public abstract class AbstractMockMvcBuilder<B extends AbstractMockMvcBuilder<B>>
@@ -55,7 +57,7 @@ public abstract class AbstractMockMvcBuilder<B extends AbstractMockMvcBuilder<B>
 
 	private final List<ResultHandler> globalResultHandlers = new ArrayList<>();
 
-	private Boolean dispatchOptions = Boolean.TRUE;
+	private final List<DispatcherServletCustomizer> dispatcherServletCustomizers = new ArrayList<>();
 
 	private final List<MockMvcConfigurer> configurers = new ArrayList<>(4);
 
@@ -104,11 +106,16 @@ public abstract class AbstractMockMvcBuilder<B extends AbstractMockMvcBuilder<B>
 	}
 
 	@SuppressWarnings("unchecked")
-	public final <T extends B> T dispatchOptions(boolean dispatchOptions) {
+	public final <T extends B> T addDispatcherServletCustomizer(DispatcherServletCustomizer customizer) {
-		this.dispatchOptions = dispatchOptions;
+		this.dispatcherServletCustomizers.add(customizer);
 		return (T) this;
 	}
 
+	public final <T extends B> T dispatchOptions(boolean dispatchOptions) {
+		return addDispatcherServletCustomizer(
+				dispatcherServlet -> dispatcherServlet.setDispatchOptionsRequest(dispatchOptions));
+	}
+
 	@SuppressWarnings("unchecked")
 	public final <T extends B> T apply(MockMvcConfigurer configurer) {
 		configurer.afterConfigurerAdded(this);
@@ -144,7 +151,7 @@ public abstract class AbstractMockMvcBuilder<B extends AbstractMockMvcBuilder<B>
 		Filter[] filterArray = this.filters.toArray(new Filter[this.filters.size()]);
 
 		return super.createMockMvc(filterArray, mockServletConfig, wac, this.defaultRequestBuilder,
-				this.globalResultMatchers, this.globalResultHandlers, this.dispatchOptions);
+				this.globalResultMatchers, this.globalResultHandlers, this.dispatcherServletCustomizers);
 	}
 
 	/**

spring-test/src/test/java/org/springframework/test/web/servlet/setup/DefaultMockMvcBuilderTests.java

@@ -20,11 +20,14 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.context.support.StaticApplicationContext;
 import org.springframework.mock.web.MockServletContext;
+import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.context.support.StaticWebApplicationContext;
 import org.springframework.web.context.support.WebApplicationContextUtils;
+import org.springframework.web.servlet.DispatcherServlet;
 
 import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
@@ -36,6 +39,7 @@ import static org.springframework.test.web.servlet.setup.MockMvcBuilders.*;
  * @author Rob Winch
  * @author Sebastien Deleuze
  * @author Sam Brannen
+ * @author Stephane Nicoll
  */
 public class DefaultMockMvcBuilderTests {
 
@@ -124,4 +128,32 @@ public class DefaultMockMvcBuilderTests {
 		assertSame(root, WebApplicationContextUtils.getRequiredWebApplicationContext(this.servletContext));
 	}
 
+	/**
+	 * See /SPR-14277
+	 */
+	@Test
+	public void dispatcherServletCustomizer() {
+		StubWebApplicationContext root = new StubWebApplicationContext(this.servletContext);
+		DefaultMockMvcBuilder builder = webAppContextSetup(root);
+		builder.addDispatcherServletCustomizer(ds -> ds.setContextId("test-id"));
+		builder.dispatchOptions(true);
+		MockMvc mvc = builder.build();
+		DispatcherServlet ds = (DispatcherServlet) new DirectFieldAccessor(mvc)
+				.getPropertyValue("servlet");
+		assertEquals("test-id", ds.getContextId());
+	}
+
+	@Test
+	public void dispatcherServletCustomizerProcessedInOrder() {
+		StubWebApplicationContext root = new StubWebApplicationContext(this.servletContext);
+		DefaultMockMvcBuilder builder = webAppContextSetup(root);
+		builder.addDispatcherServletCustomizer(ds -> ds.setContextId("test-id"));
+		builder.addDispatcherServletCustomizer(ds -> ds.setContextId("override-id"));
+		builder.dispatchOptions(true);
+		MockMvc mvc = builder.build();
+		DispatcherServlet ds = (DispatcherServlet) new DirectFieldAccessor(mvc)
+				.getPropertyValue("servlet");
+		assertEquals("override-id", ds.getContextId());
+	}
+
 }