Spring Framework example source code file (FrameworkServlet.java)

This example Spring Framework source code file (FrameworkServlet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

beansexception, configurableapplicationcontext, configurablewebapplicationcontext, context, frameworkservlet, http, httpservletresponse, io, ioexception, ioexception, request, response, security, servlet, servletexception, servletexception, string, string, webapplicationcontext, webapplicationcontext

The Spring Framework FrameworkServlet.java source code

/*
 * Copyright 2002-2008 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.context.event.SourceFilteringListener;
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;

	/** Should we dispatch an HTTP OPTIONS request to {@link #doService}? */
	private boolean dispatchOptionsRequest = false;

	/** Should we dispatch an HTTP TRACE request to {@link #doService}? */
	private boolean dispatchTraceRequest = false;

	/** 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;
	}

	/**
	 * 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;
	}

	/**
	 * Set whether this servlet should dispatch an HTTP OPTIONS request to
	 * the {@link #doService} method.
	 * <p>Default is "false", applying {@link javax.servlet.http.HttpServlet}'s
	 * default behavior (i.e. enumerating all standard HTTP request methods
	 * as a response to the OPTIONS request).
	 * <p>Turn this flag on if you prefer OPTIONS requests to go through the
	 * regular dispatching chain, just like other HTTP requests. This usually
	 * means that your controllers will receive those requests; make sure
	 * that those endpoints are actually able to handle an OPTIONS request.
	 * <p>Note that HttpServlet's default OPTIONS processing will be applied
	 * in any case. Your controllers are simply available to override the
	 * default headers and optionally generate a response body.
	 */
	public void setDispatchOptionsRequest(boolean dispatchOptionsRequest) {
		this.dispatchOptionsRequest = dispatchOptionsRequest;
	}

	/**
	 * Set whether this servlet should dispatch an HTTP TRACE request to
	 * the {@link #doService} method.
	 * <p>Default is "false", applying {@link javax.servlet.http.HttpServlet}'s
	 * default behavior (i.e. reflecting the message received back to the client).
	 * <p>Turn this flag on if you prefer TRACE requests to go through the
	 * regular dispatching chain, just like other HTTP requests. This usually
	 * means that your controllers will receive those requests; make sure
	 * that those endpoints are actually able to handle a TRACE request.
	 * <p>Note that HttpServlet's default TRACE processing will be applied
	 * in any case. Your controllers are simply available to override the
	 * default headers and the default body, calling <code>response.reset()
	 * if necessary.
	 */
	public void setDispatchTraceRequest(boolean dispatchTraceRequest) {
		this.dispatchTraceRequest = dispatchTraceRequest;
	}


	/**
	 * 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 (this.publishContext) {
			// Publish the context as a servlet context attribute.
			String attrName = getServletContextAttributeName();
			getServletContext().setAttribute(attrName, wac);
			if (logger.isDebugEnabled()) {
				logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
						"' as ServletContext attribute with name [" + attrName + "]");
			}
		}

		return wac;
	}

	/**
	 * Instantiate the WebApplicationContext for this servlet, either a default
	 * {@link org.springframework.web.context.support.XmlWebApplicationContext}
	 * or a {@link #setContextClass custom context class}, if set.
	 * <p>This implementation expects custom contexts to implement the
	 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
	 * interface. Can be overridden in subclasses.
	 * <p>Do not forget to register this servlet instance as application listener on the
	 * created context (for triggering its {@link #onRefresh callback}, and to call
	 * {@link org.springframework.context.ConfigurableApplicationContext#refresh()}
	 * before returning the context instance.
	 * @param parent the parent ApplicationContext to use, or <code>null if none
	 * @return the WebApplicationContext for this servlet
	 * @throws BeansException if the context couldn't be initialized
	 * @see org.springframework.web.context.support.XmlWebApplicationContext
	 */
	protected WebApplicationContext createWebApplicationContext(WebApplicationContext parent)
			throws BeansException {

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet with name '" + getServletName() +
					"' will try to create custom WebApplicationContext context of class '" +
					getContextClass().getName() + "'" + ", using parent context [" + parent + "]");
		}
		if (!ConfigurableWebApplicationContext.class.isAssignableFrom(getContextClass())) {
			throw new ApplicationContextException(
					"Fatal initialization error in servlet with name '" + getServletName() +
					"': custom WebApplicationContext class [" + getContextClass().getName() +
					"] is not of type ConfigurableWebApplicationContext");
		}

		ConfigurableWebApplicationContext wac =
				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(getContextClass());
		wac.setParent(parent);
		wac.setServletContext(getServletContext());
		wac.setServletConfig(getServletConfig());
		wac.setNamespace(getNamespace());
		wac.setConfigLocation(getContextConfigLocation());
		wac.addApplicationListener(new SourceFilteringListener(wac, this));

		postProcessWebApplicationContext(wac);
		wac.refresh();

		return wac;
	}

	/**
	 * Post-process the given WebApplicationContext before it is refreshed
	 * and activated as context for this servlet.
	 * <p>The default implementation is empty. refresh() will
	 * be called automatically after this method returns.
	 * @param wac the configured WebApplicationContext (not refreshed yet)
	 * @see #createWebApplicationContext
	 * @see ConfigurableWebApplicationContext#refresh()
	 */
	protected void postProcessWebApplicationContext(ConfigurableWebApplicationContext wac) {
	}

	/**
	 * Return the ServletContext attribute name for this servlet's WebApplicationContext.
	 * <p>The default implementation returns
	 * <code>SERVLET_CONTEXT_PREFIX + servlet name.
	 * @see #SERVLET_CONTEXT_PREFIX
	 * @see #getServletName
	 */
	public String getServletContextAttributeName() {
		return SERVLET_CONTEXT_PREFIX + getServletName();
	}

	/**
	 * Return this servlet's WebApplicationContext.
	 */
	public final WebApplicationContext getWebApplicationContext() {
		return this.webApplicationContext;
	}


	/**
	 * This method will be invoked after any bean properties have been set and
	 * the WebApplicationContext has been loaded. The default implementation is empty;
	 * subclasses may override this method to perform any initialization they require.
	 * @throws ServletException in case of an initialization exception
	 * @throws BeansException if thrown by ApplicationContext methods
	 */
	protected void initFrameworkServlet() throws ServletException, BeansException {
	}

	/**
	 * Refresh this servlet's application context, as well as the
	 * dependent state of the servlet.
	 * @throws BeansException in case of errors
	 * @see #getWebApplicationContext()
	 * @see org.springframework.context.ConfigurableApplicationContext#refresh()
	 */
	public void refresh() throws BeansException {
		WebApplicationContext wac = getWebApplicationContext();
		if (!(wac instanceof ConfigurableApplicationContext)) {
			throw new IllegalStateException("WebApplicationContext does not support refresh: " + wac);
		}
		((ConfigurableApplicationContext) wac).refresh();
	}

	/**
	 * ApplicationListener endpoint that receives events from this servlet's
	 * WebApplicationContext.
	 * <p>The default implementation calls {@link #onRefresh} in case of a
	 * {@link org.springframework.context.event.ContextRefreshedEvent},
	 * triggering a refresh of this servlet's context-dependent state.
	 * @param event the incoming ApplicationContext event
	 */
	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof ContextRefreshedEvent) {
			this.refreshEventReceived = true;
			onRefresh(((ContextRefreshedEvent) event).getApplicationContext());
		}
	}

	/**
	 * Template method which can be overridden to add servlet-specific refresh work.
	 * Called after successful context refresh.
	 * <p>This implementation is empty.
	 * @param context the current WebApplicationContext
	 * @throws BeansException in case of errors
	 * @see #refresh()
	 */
	protected void onRefresh(ApplicationContext context) throws BeansException {
		// For subclasses: do nothing by default.
	}


	/**
	 * Delegate GET requests to processRequest/doService.
	 * <p>Will also be invoked by HttpServlet's default implementation of doHead,
	 * with a <code>NoBodyResponse that just captures the content length.
	 * @see #doService
	 * @see #doHead
	 */
	protected final void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate POST requests to {@link #processRequest}.
	 * @see #doService
	 */
	protected final void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate PUT requests to {@link #processRequest}.
	 * @see #doService
	 */
	protected final void doPut(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate DELETE requests to {@link #processRequest}.
	 * @see #doService
	 */
	protected final void doDelete(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate OPTIONS requests to {@link #processRequest}, if desired.
	 * <p>Applies HttpServlet's standard OPTIONS processing first.
	 * @see #doService
	 */
	protected void doOptions(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		super.doOptions(request, response);
		if (this.dispatchOptionsRequest) {
			processRequest(request, response);
		}
	}

	/**
	 * Delegate TRACE requests to {@link #processRequest}, if desired.
	 * <p>Applies HttpServlet's standard TRACE processing first.
	 * @see #doService
	 */
	protected void doTrace(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		super.doTrace(request, response);
		if (this.dispatchTraceRequest) {
			processRequest(request, response);
		}
	}


	/**
	 * Process this request, publishing an event regardless of the outcome.
	 * <p>The actual event handling is performed by the abstract
	 * {@link #doService} template method.
	 */
	protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		long startTime = System.currentTimeMillis();
		Throwable failureCause = null;

		try {
			doService(request, response);
		}
		catch (ServletException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (IOException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (Throwable ex) {
			failureCause = ex;
			throw new NestedServletException("Request processing failed", ex);
		}

		finally {
			if (failureCause != null) {
				logger.debug("Could not complete request", failureCause);
			}
			else {
				logger.debug("Successfully completed request");
			}
			if (this.publishEvents) {
				// Whether or not we succeeded, publish an event.
				long processingTime = System.currentTimeMillis() - startTime;
				this.webApplicationContext.publishEvent(
						new ServletRequestHandledEvent(this,
								request.getRequestURI(), request.getRemoteAddr(),
								request.getMethod(), getServletConfig().getServletName(),
								WebUtils.getSessionId(request), getUsernameForRequest(request),
								processingTime, failureCause));
			}
		}
	}

	/**
	 * Determine the username for the given request.
	 * <p>The default implementation takes the name of the UserPrincipal, if any.
	 * Can be overridden in subclasses.
	 * @param request current HTTP request
	 * @return the username, or <code>null if none found
	 * @see javax.servlet.http.HttpServletRequest#getUserPrincipal()
	 */
	protected String getUsernameForRequest(HttpServletRequest request) {
		Principal userPrincipal = request.getUserPrincipal();
		return (userPrincipal != null ? userPrincipal.getName() : null);
	}

	/**
	 * Subclasses must implement this method to do the work of request handling,
	 * receiving a centralized callback for GET, POST, PUT and DELETE.
	 * <p>The contract is essentially the same as that for the commonly overridden
	 * <code>doGet or doPost methods of HttpServlet.
	 * <p>This class intercepts calls to ensure that exception handling and
	 * event publication takes place.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws Exception in case of any kind of processing failure
	 * @see javax.servlet.http.HttpServlet#doGet
	 * @see javax.servlet.http.HttpServlet#doPost
	 */
	protected abstract void doService(HttpServletRequest request, HttpServletResponse response)
	    throws Exception;


	/**
	 * Close the WebApplicationContext of this servlet.
	 * @see org.springframework.context.ConfigurableApplicationContext#close()
	 */
	public void destroy() {
		getServletContext().log("Destroying Spring FrameworkServlet '" + getServletName() + "'");
		if (this.webApplicationContext instanceof ConfigurableApplicationContext) {
			((ConfigurableApplicationContext) this.webApplicationContext).close();
		}
	}

}