DelegatingFilterProxy looks at "registered" WebApplicationContexts

Previously when users registered an additional Filter in the
DispatcherServlet the DelegatingFilterProxy would not find it unless
the context attribute was set. The value for which was difficult to
remember and added quite a bit of additional "if" statements to setting
up Spring Security successfully.

This change allows registering additional known WebApplicationContext
instances. The DispatcherServlet uses this mechanism to register its
context. With that change DelegatingFilterProxy searches for the first
registered WebApplicationContext that contains the bean name.

This change also sets up the ability for Spring Security to lookup
Beans defined in the child context within the Tag libs.

Issue: SPR-13191

Author: Rob Winch

spring-web/src/main/java/org/springframework/web/context/support/WebApplicationContextUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -17,9 +17,12 @@
 package org.springframework.web.context.support;
 
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import javax.faces.context.ExternalContext;
 import javax.faces.context.FacesContext;
@@ -55,6 +58,7 @@
  * This helper class is just the most generic way to access the root context.
  *
  * @author Juergen Hoeller
+ * @author Rob Winch
  * @see org.springframework.web.context.ContextLoader
  * @see org.springframework.web.servlet.FrameworkServlet
  * @see org.springframework.web.servlet.DispatcherServlet
@@ -63,6 +67,13 @@
  */
 public abstract class WebApplicationContextUtils {
 
+	/**
+	 * The attribute that all attribute names for all registered WebApplicationContext is
+	 * stored. This only includes WebApplicationContext that are stored using
+	 * registerWebApplicationContext
+	 */
+	private static final String APPLICATION_CONTEXT_ATTRIBUTES_ATTRIBUTE = WebApplicationContextUtils.class.getName().concat(".APPLICATION_CONTEXT_ATTRIBUTES_ATTRIBUTE");
+
 	private static final boolean jsfPresent =
 			ClassUtils.isPresent("javax.faces.context.FacesContext", RequestContextHolder.class.getClassLoader());
 
@@ -125,6 +136,63 @@ public static WebApplicationContext getWebApplicationContext(ServletContext sc,
 		return (WebApplicationContext) attr;
 	}
 
+	/**
+	 * Register a custom {@link WebApplicationContext} for this web app.
+	 * @param sc ServletContext to find the web application context for
+	 * @param attrName the name of the ServletContext attribute to use
+	 * @param context the desired WebApplicationContext to store
+	 * @since 4.2
+	 */
+	public static void registerWebApplicationContext(ServletContext sc, String attrName, WebApplicationContext context) {
+		Assert.notNull(sc, "ServletContext must not be null");
+		Assert.notNull(attrName, "attrName must not be null");
+		Assert.notNull(context, "WebApplicationContext must not be null");
+
+		sc.setAttribute(attrName, context);
+
+		@SuppressWarnings("unchecked")
+		LinkedHashSet<String> attrNames = (LinkedHashSet<String>) sc.getAttribute(APPLICATION_CONTEXT_ATTRIBUTES_ATTRIBUTE);
+		if (attrNames == null) {
+			attrNames = new LinkedHashSet<String>();
+		}
+
+		attrNames.add(attrName);
+		sc.setAttribute(APPLICATION_CONTEXT_ATTRIBUTES_ATTRIBUTE, attrNames);
+	}
+
+	/**
+	 * Gets all the known {@link WebApplicationContext} for this web app. The order is the
+	 * root context (if specified) followed by any context registered using
+	 * registerWebApplicationContext in the order they were registered.
+	 *
+	 * @param sc ServletContext to find the web application context for. Cannot be null.
+	 * @return the known {@link WebApplicationContext} for this web app. Cannot be null,
+	 * but may be empty.
+	 * @since 4.2
+	 */
+	public static List<WebApplicationContext> getRegisteredWebApplicationContexts(ServletContext sc) {
+		Assert.notNull(sc, "ServletContext must not be null");
+
+		List<WebApplicationContext> result = new ArrayList<WebApplicationContext>();
+
+		WebApplicationContext root = getWebApplicationContext(sc);
+		if (root != null) {
+			result.add(root);
+		}
+
+		@SuppressWarnings("unchecked")
+		LinkedHashSet<String> attrNames = (LinkedHashSet<String>) sc.getAttribute(APPLICATION_CONTEXT_ATTRIBUTES_ATTRIBUTE);
+		if (attrNames == null) {
+			return result;
+		}
+
+		for (String attrName : attrNames) {
+			WebApplicationContext context = getWebApplicationContext(sc, attrName);
+			result.add(context);
+		}
+
+		return result;
+	}
 
 	/**
 	 * Register web-specific scopes ("request", "session", "globalSession")

spring-web/src/main/java/org/springframework/web/filter/DelegatingFilterProxy.java

@@ -17,6 +17,7 @@
 package org.springframework.web.filter;
 
 import java.io.IOException;
+import java.util.List;
 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
@@ -66,6 +67,7 @@
  * @author Juergen Hoeller
  * @author Sam Brannen
  * @author Chris Beams
+ * @author Rob Winch
  * @since 1.2
  * @see #setTargetBeanName
  * @see #setTargetFilterLifecycle
@@ -275,7 +277,9 @@ public void destroy() {
 	 * Otherwise, attempt to retrieve a {@code WebApplicationContext} from the
 	 * {@code ServletContext} attribute with the {@linkplain #setContextAttribute
 	 * configured name} if set. Otherwise look up a {@code WebApplicationContext} under
-	 * the well-known "root" application context attribute. The
+	 * the well-known "root" application context attribute. If no "root" application
+	 * context exists or the bean name is undefined in the "root", then the first "registered"
+	 * application context that contains the bean name is used. The
 	 * {@code WebApplicationContext} must have already been loaded and stored in the
 	 * {@code ServletContext} before this filter gets initialized (or invoked).
 	 * <p>Subclasses may override this method to provide a different
@@ -301,9 +305,14 @@ protected WebApplicationContext findWebApplicationContext() {
 		if (attrName != null) {
 			return WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
 		}
-		else {
-			return WebApplicationContextUtils.getWebApplicationContext(getServletContext());
+
+		List<WebApplicationContext> registered = WebApplicationContextUtils.getRegisteredWebApplicationContexts(getServletContext());
+		for (WebApplicationContext context : registered) {
+			if (context.containsBean(targetBeanName)) {
+				return context;
+			}
 		}
+		return null;
 	}
 
 	/**

spring-web/src/test/java/org/springframework/web/context/support/WebApplicationContextUtilsTests.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2002-2015 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.context.support;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+import static org.junit.Assert.*;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.mock.web.test.MockServletContext;
+import org.springframework.web.context.WebApplicationContext;
+
+/**
+ * @author Rob Winch
+ */
+public class WebApplicationContextUtilsTests {
+	private MockServletContext sc;
+
+	private String attrName;
+	private String attrName2;
+
+	private AnnotationConfigWebApplicationContext rootContext;
+	private AnnotationConfigWebApplicationContext context;
+	private AnnotationConfigWebApplicationContext context2;
+
+	@Before
+	public void setup() {
+		sc = new MockServletContext();
+		attrName = "attrName";
+		attrName2 = "attrName2";
+		rootContext = new AnnotationConfigWebApplicationContext();
+		context = new AnnotationConfigWebApplicationContext();
+		context2 = new AnnotationConfigWebApplicationContext();
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void registerWebApplicationContextNullSc() {
+		WebApplicationContextUtils.registerWebApplicationContext(null, attrName, context);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void registerWebApplicationContextNullAttrName() {
+		WebApplicationContextUtils.registerWebApplicationContext(sc, null, context);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void registerWebApplicationContextNullContext() {
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, null);
+	}
+
+	@Test
+	public void registerWebApplicationContextNoRoot() {
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, context);
+
+		assertEquals(Arrays.asList(context),
+				WebApplicationContextUtils.getRegisteredWebApplicationContexts(sc));
+	}
+
+	@Test
+	public void registerWebApplicationContextWithRoot() {
+		sc.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, rootContext);
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, context);
+
+		assertEquals(Arrays.asList(rootContext, context),
+				WebApplicationContextUtils.getRegisteredWebApplicationContexts(sc));
+	}
+
+	@Test
+	public void registerWebApplicationContextMultiChild() {
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, context);
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName2, context2);
+		sc.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, rootContext);
+
+		assertEquals(Arrays.asList(rootContext, context, context2),
+				WebApplicationContextUtils.getRegisteredWebApplicationContexts(sc));
+	}
+
+	@Test
+	public void registerWebApplicationContextMultiWithSameAttr() {
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, context);
+		WebApplicationContextUtils.registerWebApplicationContext(sc, attrName, context2);
+
+		assertEquals(Arrays.asList(context2),
+				WebApplicationContextUtils.getRegisteredWebApplicationContexts(sc));
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void getRegisteredWebApplicationContextNull() {
+		WebApplicationContextUtils.getRegisteredWebApplicationContexts(null);
+	}
+
+	@Test
+	public void getRegisteredWebApplicationContext() {
+		assertEquals(Collections.emptyList(),
+				WebApplicationContextUtils.getRegisteredWebApplicationContexts(sc));
+	}
+}