Initial cut of Servlet 3.0 based async support

From a programming model perspective, @RequestMapping methods now
support two new return value types:

* java.util.concurrent.Callable - used by Spring MVC to obtain the
return value asynchronously in a separate thread managed transparently
by Spring MVC on behalf of the application.
* org.springframework.web.context.request.async.DeferredResult - used
by the application to produce the return value asynchronously in a
separate thread of its own choosing.

The high-level idea is that whatever value a controller normally
returns, it can now provide it asynchronously, through a Callable or
through a DeferredResult, with all remaining processing --
@ResponseBody, view resolution, etc, working just the same but
completed outside the main request thread.

From an SPI perspective, there are several new types:

* AsyncExecutionChain - the central class for managing async request
processing through a sequence of Callable instances each representing
work required to complete request processing asynchronously.
* AsyncWebRequest - provides methods for starting, completing, and
configuring async request processing.
* StandardServletAsyncWebRequest - Servlet 3 based implementation.
* AsyncExecutionChainRunnable - the Runnable used for async request
execution.

All spring-web and spring-webmvc Filter implementations have been
updated to participate in async request execution.
The open-session-in-view Filter and interceptors implementations in
spring-orm will be updated in a separate pull request.

Issue: SPR-8517

spring-webmvc/src/test/java/org/springframework/web/servlet/HandlerExecutionChainTests.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2002-2012 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;
+
+import static org.easymock.EasyMock.createMock;
+import static org.easymock.EasyMock.expect;
+import static org.easymock.EasyMock.replay;
+import static org.easymock.EasyMock.verify;
+import static org.junit.Assert.assertSame;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+/**
+ * A test fixture with HandlerExecutionChain and mock handler interceptors.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class HandlerExecutionChainTests {
+
+	private HandlerExecutionChain chain;
+
+	private Object handler;
+
+	private MockHttpServletRequest request;
+
+	private MockHttpServletResponse response;
+
+	private HandlerInterceptor interceptor1;
+
+	private HandlerInterceptor interceptor2;
+
+	private HandlerInterceptor interceptor3;
+
+	@Before
+	public void setup() {
+		this.request = new MockHttpServletRequest();
+		this.response= new MockHttpServletResponse() ;
+
+		this.handler = new Object();
+		this.chain = new HandlerExecutionChain(this.handler);
+
+		this.interceptor1 = createMock(HandlerInterceptor.class);
+		this.interceptor2 = createMock(HandlerInterceptor.class);
+		this.interceptor3 = createMock(HandlerInterceptor.class);
+
+		this.chain.addInterceptor(this.interceptor1);
+		this.chain.addInterceptor(this.interceptor2);
+		this.chain.addInterceptor(this.interceptor3);
+	}
+
+	@Test
+	public void successScenario() throws Exception {
+		ModelAndView mav = new ModelAndView();
+
+		expect(this.interceptor1.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor2.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor3.preHandle(this.request, this.response, this.handler)).andReturn(true);
+
+		this.interceptor1.postHandle(this.request, this.response, this.handler, mav);
+		this.interceptor2.postHandle(this.request, this.response, this.handler, mav);
+		this.interceptor3.postHandle(this.request, this.response, this.handler, mav);
+
+		this.interceptor3.afterCompletion(this.request, this.response, this.handler, null);
+		this.interceptor2.afterCompletion(this.request, this.response, this.handler, null);
+		this.interceptor1.afterCompletion(this.request, this.response, this.handler, null);
+
+		replay(this.interceptor1, this.interceptor2, this.interceptor3);
+
+		this.chain.applyPreHandle(request, response);
+		this.chain.applyPostHandle(request, response, mav);
+		this.chain.triggerAfterCompletion(this.request, this.response, null);
+
+		verify(this.interceptor1, this.interceptor2, this.interceptor3);
+	}
+
+	@Test
+	public void earlyExit() throws Exception {
+		expect(this.interceptor1.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor2.preHandle(this.request, this.response, this.handler)).andReturn(false);
+
+		this.interceptor1.afterCompletion(this.request, this.response, this.handler, null);
+
+		replay(this.interceptor1, this.interceptor2, this.interceptor3);
+
+		this.chain.applyPreHandle(request, response);
+
+		verify(this.interceptor1, this.interceptor2, this.interceptor3);
+	}
+
+	@Test
+	public void exceptionBeforePreHandle() throws Exception {
+		replay(this.interceptor1, this.interceptor2, this.interceptor3);
+
+		this.chain.triggerAfterCompletion(this.request, this.response, null);
+
+		verify(this.interceptor1, this.interceptor2, this.interceptor3);
+	}
+
+	@Test
+	public void exceptionDuringPreHandle() throws Exception {
+		Exception ex = new Exception("");
+
+		expect(this.interceptor1.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor2.preHandle(this.request, this.response, this.handler)).andThrow(ex);
+
+		this.interceptor1.afterCompletion(this.request, this.response, this.handler, ex);
+
+		replay(this.interceptor1, this.interceptor2, this.interceptor3);
+
+		try {
+			this.chain.applyPreHandle(request, response);
+		}
+		catch (Exception actual) {
+			assertSame(ex, actual);
+		}
+		this.chain.triggerAfterCompletion(this.request, this.response, ex);
+
+		verify(this.interceptor1, this.interceptor2, this.interceptor3);
+	}
+
+	@Test
+	public void exceptionAfterPreHandle() throws Exception {
+		Exception ex = new Exception("");
+
+		expect(this.interceptor1.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor2.preHandle(this.request, this.response, this.handler)).andReturn(true);
+		expect(this.interceptor3.preHandle(this.request, this.response, this.handler)).andReturn(true);
+
+		this.interceptor3.afterCompletion(this.request, this.response, this.handler, ex);
+		this.interceptor2.afterCompletion(this.request, this.response, this.handler, ex);
+		this.interceptor1.afterCompletion(this.request, this.response, this.handler, ex);
+
+		replay(this.interceptor1, this.interceptor2, this.interceptor3);
+
+		this.chain.applyPreHandle(request, response);
+		this.chain.triggerAfterCompletion(this.request, this.response, ex);
+
+		verify(this.interceptor1, this.interceptor2, this.interceptor3);
+	}
+
+}