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Spring Framework example source code file (HandlerInterceptor.java)

This example Spring Framework source code file (HandlerInterceptor.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

actionrequest, actionresponse, exception, exception, handlerinterceptor, modelandview, object, object, renderrequest, renderrequest, renderresponse, renderresponse

The Spring Framework HandlerInterceptor.java source code

/*
 * 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.portlet;

import javax.portlet.ActionRequest;
import javax.portlet.ActionResponse;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;

/**
 * Workflow interface that allows for customized handler execution chains.
 * Applications can register any number of existing or custom interceptors
 * for certain groups of handlers, to add common pre-processing behavior
 * without needing to modify each handler implementation.
 *
 * <p>A HandlerInterceptor gets called before the appropriate
 * {@link org.springframework.web.portlet.HandlerAdapter} triggers the
 * execution of the handler itself. This mechanism can be used for a large
 * field of preprocessing aspects, e.g. for authorization checks,
 * or common handler behavior like locale or theme changes. Its main purpose
 * is to permit the factoring out of otherwise repetitive handler code.
 *
 * <p>Typically an interceptor chain is defined per
 * {@link org.springframework.web.portlet.HandlerMapping} bean, sharing its
 * granularity. To be able to apply a certain interceptor chain to a group of
 * handlers, one needs to map the desired handlers via one
 * <code>HandlerMapping bean. The interceptors themselves are defined as
 * beans in the application context, referenced by the mapping bean definition
 * via its
 * {@link org.springframework.web.portlet.handler.AbstractHandlerMapping#setInterceptors "interceptors"}
 * property (in XML: a <list> of <ref> elements).
 *
 * <p>A HandlerInterceptor is basically similar to a Servlet
 * {@link javax.servlet.Filter}, but in contrast to the latter it allows
 * custom pre-processing with the option to prohibit the execution of the handler
 * itself, and custom post-processing. <code>Filters are more powerful;
 * for example they allow for exchanging the request and response objects that
 * are handed down the chain. Note that a filter gets configured in
 * <code>web.xml, a HandlerInterceptor in the application context.
 *
 * <p>As a basic guideline, fine-grained handler-related pre-processing tasks are
 * candidates for <code>HandlerInterceptor implementations, especially
 * factored-out common handler code and authorization checks. On the other hand,
 * a <code>Filter is well-suited for request content and view content
 * handling, like multipart forms and GZIP compression. This typically shows when
 * one needs to map the filter to certain content types (e.g. images), or to all
 * requests.
 *
 * <p>Be aware that filters cannot be applied to portlet requests (they
 * only operate on servlet requests), so for portlet requests interceptors are
 * essential.
 *
 * <p>If we assume a "sunny day" request cycle (i.e. a request where nothing goes wrong
 * and all is well), the workflow of a <code>HandlerInterceptor will be as
 * follows:
 *
 * <p>Action Request:

* <ol> * <li>DispatcherPortlet maps the action request to a particular handler * and assembles a handler execution chain consisting of the handler that * is to be invoked and all of the <code>HandlerInterceptor * instances that apply to the request.</li> * <li>{@link org.springframework.web.portlet.HandlerInterceptor#preHandleAction(javax.portlet.ActionRequest, javax.portlet.ActionResponse, Object) preHandleAction(..)} * is called; if the invocation of this method returns <code>true then * this workflow continues</li> * <li>The target handler handles the action request (via * {@link org.springframework.web.portlet.HandlerAdapter#handleAction(javax.portlet.ActionRequest, javax.portlet.ActionResponse, Object) HandlerAdapter.handleAction(..)})</li> * <li>{@link org.springframework.web.portlet.HandlerInterceptor#afterActionCompletion(javax.portlet.ActionRequest, javax.portlet.ActionResponse, Object, Exception) afterActionCompletion(..)} * is called</li> * </ol> * * <p>Render Request:

* <ol> * <li>DispatcherPortlet maps the render request to a particular handler * and assembles a handler execution chain consisting of the handler that * is to be invoked and all of the <code>HandlerInterceptor * instances that apply to the request.</li> * <li>{@link org.springframework.web.portlet.HandlerInterceptor#preHandleRender(javax.portlet.RenderRequest, javax.portlet.RenderResponse, Object) preHandleRender(..)} * is called; if the invocation of this method returns <code>true then * this workflow continues</li> * <li>The target handler handles the render request (via * {@link org.springframework.web.portlet.HandlerAdapter#handleRender(javax.portlet.RenderRequest, javax.portlet.RenderResponse, Object) HandlerAdapter.handleRender(..)})</li> * <li>{@link org.springframework.web.portlet.HandlerInterceptor#postHandleRender(javax.portlet.RenderRequest, javax.portlet.RenderResponse, Object, ModelAndView) postHandleRender(..)} * is called</li> * <li>If the HandlerAdapter returned a ModelAndView, * then <code>DispatcherPortlet renders the view accordingly * <li>{@link org.springframework.web.portlet.HandlerInterceptor#afterRenderCompletion(javax.portlet.RenderRequest, javax.portlet.RenderResponse, Object, Exception) afterRenderCompletion(..)} * is called</li> * </ol> * * @author Juergen Hoeller * @author John A. Lewis * @since 2.0 * @see HandlerExecutionChain#getInterceptors * @see org.springframework.web.portlet.HandlerMapping * @see org.springframework.web.portlet.handler.AbstractHandlerMapping#setInterceptors * @see org.springframework.web.portlet.HandlerExecutionChain */ public interface HandlerInterceptor { /** * Intercept the execution of a handler in the action phase. * <p>Called after a HandlerMapping determines an appropriate handler object * to handle an {@link ActionRequest}, but before said HandlerAdapter actually * invokes the handler. * <p>{@link DispatcherPortlet} processes a handler in an execution chain, * consisting of any number of interceptors, with the handler itself at the end. * With this method, each interceptor can decide to abort the execution chain, * typically throwing an exception or writing a custom response. * @param request current portlet action request * @param response current portlet action response * @param handler chosen handler to execute, for type and/or instance evaluation * @return <code>true if the execution chain should proceed with the * next interceptor or the handler itself. Else, <code>DispatcherPortlet * assumes that this interceptor has already dealt with the response itself * @throws Exception in case of errors */ boolean preHandleAction(ActionRequest request, ActionResponse response, Object handler) throws Exception; /** * Callback after completion of request processing in the action phase, that is, * after rendering the view. Will be called on any outcome of handler execution, * thus allowing for proper resource cleanup. * <p>Note: Will only be called if this interceptor's * {@link #preHandleAction(javax.portlet.ActionRequest, javax.portlet.ActionResponse, Object)} * method has successfully completed and returned <code>true! * @param request current portlet action request * @param response current portlet action response * @param handler chosen handler to execute, for type and/or instance examination * @param ex exception thrown on handler execution, if any (only included as * additional context information for the case where a handler threw an exception; * request execution may have failed even when this argument is <code>null) * @throws Exception in case of errors */ void afterActionCompletion( ActionRequest request, ActionResponse response, Object handler, Exception ex) throws Exception; /** * Intercept the execution of a handler in the render phase. * <p>Called after a HandlerMapping determines an appropriate handler object * to handle a {@link RenderRequest}, but before said HandlerAdapter actually * invokes the handler. * <p>{@link DispatcherPortlet} processes a handler in an execution chain, * consisting of any number of interceptors, with the handler itself at the end. * With this method, each interceptor can decide to abort the execution chain, * typically throwing an exception or writing a custom response. * @param request current portlet render request * @param response current portlet render response * @param handler chosen handler to execute, for type and/or instance evaluation * @return <code>true if the execution chain should proceed with the * next interceptor or the handler itself. Else, <code>DispatcherPortlet * assumes that this interceptor has already dealt with the response itself * @throws Exception in case of errors */ boolean preHandleRender(RenderRequest request, RenderResponse response, Object handler) throws Exception; /** * Intercept the execution of a handler in the render phase. * <p>Called after a {@link HandlerAdapter} actually invoked the handler, but * before the <code>DispatcherPortlet renders the view. Can thus expose * additional model objects to the view via the given {@link ModelAndView}. * <p>DispatcherPortlet processes a handler in an execution chain, * consisting of any number of interceptors, with the handler itself at the end. * With this method, each interceptor can post-process an execution, getting * applied in inverse order of the execution chain. * @param request current portlet render request * @param response current portlet render response * @param handler chosen handler to execute, for type and/or instance examination * @param modelAndView the <code>ModelAndView that the handler returned * (can also be <code>null) * @throws Exception in case of errors */ void postHandleRender( RenderRequest request, RenderResponse response, Object handler, ModelAndView modelAndView) throws Exception; /** * Callback after completion of request processing, that is, after rendering * the view. Will be called on any outcome of handler execution, thus allowing * for proper resource cleanup. * <p>Note: Will only be called if this interceptor's * {@link #preHandleRender(javax.portlet.RenderRequest, javax.portlet.RenderResponse, Object)} * method has successfully completed and returned <code>true! * @param request current portlet render request * @param response current portlet render response * @param handler chosen handler to execute, for type and/or instance examination * @param ex exception thrown on handler execution, if any * @throws Exception in case of errors */ void afterRenderCompletion( RenderRequest request, RenderResponse response, Object handler, Exception ex) throws Exception; }

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