frameworkservlet.java

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/*
 * Copyright 2002-2007 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 java.io.IOException;
import java.security.Principal;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.util.StringUtils;
import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.ServletRequestHandledEvent;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.context.support.XmlWebApplicationContext;
import org.springframework.web.util.NestedServletException;
import org.springframework.web.util.WebUtils;

/**
 * Base servlet for Spring's web framework. Provides integration with
 * a Spring application context, in a JavaBean-based overall solution.
 *
 * <p>This class offers the following functionality:
 * <ul>
 * <li>Manages a {@link org.springframework.web.context.WebApplicationContext}
 * instance per servlet. The servlet's configuration is determined by beans
 * in the servlet's namespace.
 * <li>Publishes events on request processing, whether or not a request is
 * successfully handled.
 * </ul>
 *
 * <p>Subclasses must implement {@link #doService} to handle requests. Because this extends
 * {@link HttpServletBean} rather than HttpServlet directly, bean properties are
 * automatically mapped onto it. Subclasses can override {@link #initFrameworkServlet()}
 * for custom initialization.
 *
 * <p>Detects a "contextClass" parameter at the servlet init-param level,
 * falling back to the default context class,
 * {@link org.springframework.web.context.support.XmlWebApplicationContext},
 * if not found. Note that, with the default FrameworkServlet,
 * a custom context class needs to implement the
 * {@link org.springframework.web.context.ConfigurableWebApplicationContext} SPI.
 *
 * <p>Passes a "contextConfigLocation" servlet init-param to the context instance,
 * parsing it into potentially multiple file paths which can be separated by any
 * number of commas and spaces, like "test-servlet.xml, myServlet.xml".
 * If not explicitly specified, the context implementation is supposed to build a
 * default location from the namespace of the servlet.
 *
 * <p>Note: In case of multiple config locations, later bean definitions will
 * override ones defined in earlier loaded files, at least when using Spring's
 * default ApplicationContext implementation. This can be leveraged to
 * deliberately override certain bean definitions via an extra XML file.
 *
 * <p>The default namespace is "'servlet-name'-servlet", e.g. "test-servlet" for a
 * servlet-name "test" (leading to a "/WEB-INF/test-servlet.xml" default location
 * with XmlWebApplicationContext). The namespace can also be set explicitly via
 * the "namespace" servlet init-param.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #doService
 * @see #setContextClass
 * @see #setContextConfigLocation
 * @see #setNamespace
 */
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationListener {

	/**
	 * Suffix for WebApplicationContext namespaces. If a servlet of this class is
	 * given the name "test" in a context, the namespace used by the servlet will
	 * resolve to "test-servlet".
	 */
	public static final String DEFAULT_NAMESPACE_SUFFIX = "-servlet";

	/**
	 * Default context class for FrameworkServlet.
	 * @see org.springframework.web.context.support.XmlWebApplicationContext
	 */
	public static final Class DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;

	/**
	 * Prefix for the ServletContext attribute for the WebApplicationContext.
	 * The completion is the servlet name.
	 */
	public static final String SERVLET_CONTEXT_PREFIX = FrameworkServlet.class.getName() + ".CONTEXT.";


	/** WebApplicationContext implementation class to use */
	private Class contextClass = DEFAULT_CONTEXT_CLASS;

	/** Namespace for this servlet */
	private String namespace;

	/** Explicit context config location */
	private String contextConfigLocation;

	/** Should we publish the context as a ServletContext attribute? */
	private boolean publishContext = true;

	/** Should we publish a ServletRequestHandledEvent at the end of each request? */
	private boolean publishEvents = true;

	/** WebApplicationContext for this servlet */
	private WebApplicationContext webApplicationContext;

	/** Flag used to detect whether onRefresh has already been called */
	private boolean refreshEventReceived = false;


	/**
	 * Set a custom context class. This class must be of type
	 * {@link org.springframework.web.context.WebApplicationContext}.
	 * <p>When using the default FrameworkServlet implementation,
	 * the context class must also implement the
	 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
	 * interface.
	 * @see #createWebApplicationContext
	 */
	public void setContextClass(Class contextClass) {
		this.contextClass = contextClass;
	}

	/**
	 * Return the custom context class.
	 */
	public Class getContextClass() {
		return this.contextClass;
	}

	/**
	 * Set a custom namespace for this servlet,
	 * to be used for building a default context config location.
	 */
	public void setNamespace(String namespace) {
		this.namespace = namespace;
	}

	/**
	 * Return the namespace for this servlet, falling back to default scheme if
	 * no custom namespace was set: e.g. "test-servlet" for a servlet named "test".
	 */
	public String getNamespace() {
		return (this.namespace != null) ? this.namespace : getServletName() + DEFAULT_NAMESPACE_SUFFIX;
	}

	/**
	 * Set the context config location explicitly, instead of relying on the default
	 * location built from the namespace. This location string can consist of
	 * multiple locations separated by any number of commas and spaces.
	 */
	public void setContextConfigLocation(String contextConfigLocation) {
		this.contextConfigLocation = contextConfigLocation;
	}

	/**
	 * Return the explicit context config location, if any.
	 */
	public String getContextConfigLocation() {
		return this.contextConfigLocation;
	}

	/**
	 * Set whether to publish this servlet's context as a ServletContext attribute,
	 * available to all objects in the web container. Default is "true".
	 * <p>This is especially handy during testing, although it is debatable whether
	 * it's good practice to let other application objects access the context this way.
	 */
	public void setPublishContext(boolean publishContext) {
		this.publishContext = publishContext;
	}

	/**
	 * Return whether to publish this servlet's context as a ServletContext attribute.
	 */
	public boolean isPublishContext() {
		return this.publishContext;
	}

	/**
	 * Set whether this servlet should publish a ServletRequestHandledEvent at the end
	 * of each request. Default is "true"; can be turned off for a slight performance
	 * improvement, provided that no ApplicationListeners rely on such events.
	 * @see org.springframework.web.context.support.ServletRequestHandledEvent
	 */
	public void setPublishEvents(boolean publishEvents) {
		this.publishEvents = publishEvents;
	}

	/**
	 * Return whether this servlet should publish a ServletRequestHandledEvent
	 * at the end of each request.
	 */
	public boolean isPublishEvents() {
		return this.publishEvents;
	}


	/**
	 * Overridden method of {@link HttpServletBean}, invoked after any bean properties
	 * have been set. Creates this servlet's WebApplicationContext.
	 */
	protected final void initServletBean() throws ServletException, BeansException {
		getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
		if (logger.isInfoEnabled()) {
			logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
		}
		long startTime = System.currentTimeMillis();

		try {
			this.webApplicationContext = initWebApplicationContext();
			initFrameworkServlet();
		}
		catch (ServletException ex) {
			logger.error("Context initialization failed", ex);
			throw ex;
		}
		catch (BeansException ex) {
			logger.error("Context initialization failed", ex);
			throw ex;
		}

		if (logger.isInfoEnabled()) {
			long elapsedTime = System.currentTimeMillis() - startTime;
			logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
					elapsedTime + " ms");
		}
	}

	/**
	 * Initialize and publish the WebApplicationContext for this servlet.
	 * <p>Delegates to {@link #createWebApplicationContext} for actual creation
	 * of the context. Can be overridden in subclasses.
	 * @return the WebApplicationContext instance
	 * @throws BeansException if the context couldn't be initialized
	 * @see #setContextClass
	 * @see #setContextConfigLocation
	 */
	protected WebApplicationContext initWebApplicationContext() throws BeansException {
		WebApplicationContext parent = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = createWebApplicationContext(parent);

		if (!this.refreshEventReceived) {
			// Apparently not a ConfigurableApplicationContext with refresh support:
			// triggering initial onRefresh manually here.
			onRefresh(wac);
		}

		if (isPublishContext()) {
			// Publish the context as a servlet context attribute.
			String attrName = getServletContextAttributeName();
			getServletContext().setAttribute(attrName, wac);