【Java Web开发学习】Spring MVC 拦截器HandlerInterceptor

【Java Web开发学习】Spring MVC 拦截器HandlerInterceptor

转载：https://www.cnblogs.com/yangchongxing/p/9324119.html

目录

1、拦截器接口代码
2、拦截器方法调用顺序
3、自定义拦截器实现
4、拦截器配置

正文

1、拦截器接口代码

/*
 * Copyright 2002-2016 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 javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.method.HandlerMethod;

/**
 * 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 preprocessing behavior
 * without needing to modify each handler implementation.
 *
 * <p>A HandlerInterceptor gets called before the appropriate 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 allow for factoring out repetitive handler code.
 *
 * <p>In an asynchronous processing scenario, the handler may be executed in a
 * separate thread while the main thread exits without rendering or invoking the
 * {@code postHandle} and {@code afterCompletion} callbacks. When concurrent
 * handler execution completes, the request is dispatched back in order to
 * proceed with rendering the model and all methods of this contract are invoked
 * again. For further options and details see
 * {@code org.springframework.web.servlet.AsyncHandlerInterceptor}
 *
 * <p>Typically an interceptor chain is defined per 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
 * HandlerMapping bean. The interceptors themselves are defined as beans
 * in the application context, referenced by the mapping bean definition
 * via its "interceptors" property (in XML: a &lt;list&gt; of &lt;ref&gt;).
 *
 * <p>HandlerInterceptor is basically similar to a Servlet Filter, but in
 * contrast to the latter it just allows custom pre-processing with the option
 * of prohibiting the execution of the handler itself, and custom post-processing.
 * 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 web.xml, a HandlerInterceptor in the application context.
 *
 * <p>As a basic guideline, fine-grained handler-related preprocessing tasks are
 * candidates for HandlerInterceptor implementations, especially factored-out
 * common handler code and authorization checks. On the other hand, a 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.
 *
 * @author Juergen Hoeller
 * @since 20.06.2003
 * @see HandlerExecutionChain#getInterceptors
 * @see org.springframework.web.servlet.handler.HandlerInterceptorAdapter
 * @see org.springframework.web.servlet.handler.AbstractHandlerMapping#setInterceptors
 * @see org.springframework.web.servlet.handler.UserRoleAuthorizationInterceptor
 * @see org.springframework.web.servlet.i18n.LocaleChangeInterceptor
 * @see org.springframework.web.servlet.theme.ThemeChangeInterceptor
 * @see javax.servlet.Filter
 */
public interface HandlerInterceptor {

    /**
     * Intercept the execution of a handler. Called after HandlerMapping determined
     * an appropriate handler object, but before HandlerAdapter invokes the handler.
     * <p>DispatcherServlet 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 sending a HTTP error or writing a custom response.
     * <p><strong>Note:</strong> special considerations apply for asynchronous
     * request processing. For more details see
     * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.
     * @param request current HTTP request
     * @param response current HTTP 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, DispatcherServlet assumes
     * that this interceptor has already dealt with the response itself.
     * @throws Exception in case of errors
     */
    boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception;

    /**
     * Intercept the execution of a handler. Called after HandlerAdapter actually
     * invoked the handler, but before the DispatcherServlet renders the view.
     * Can expose additional model objects to the view via the given ModelAndView.
     * <p>DispatcherServlet 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.
     * <p><strong>Note:</strong> special considerations apply for asynchronous
     * request processing. For more details see
     * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handler handler (or {@link HandlerMethod}) that started asynchronous
     * execution, 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 postHandle(
            HttpServletRequest request, HttpServletResponse 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 allows
     * for proper resource cleanup.
     * <p>Note: Will only be called if this interceptor's {@code preHandle}
     * method has successfully completed and returned {@code true}!
     * <p>As with the {@code postHandle} method, the method will be invoked on each
     * interceptor in the chain in reverse order, so the first interceptor will be
     * the last to be invoked.
     * <p><strong>Note:</strong> special considerations apply for asynchronous
     * request processing. For more details see
     * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handler handler (or {@link HandlerMethod}) that started asynchronous
     * execution, for type and/or instance examination
     * @param ex exception thrown on handler execution, if any
     * @throws Exception in case of errors
     */
    void afterCompletion(
            HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception;

}

2、拦截器方法调用顺序

preHandle：在Controller方法调用之前执行，主要进行初始化操作。返回值：true表示继续流程，false表示流程中断。
postHandle：在Controller方法调用之后渲染视图之前执行。
afterCompletion：整个请求处理完毕，视图渲染完成后执行。

3、自定义拦截器实现

Spring提供了适配器HandlerInterceptorAdapter，我们只要实现适配器中需要的方法即可

public class AuthenticationInterceptor extends HandlerInterceptorAdapter {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object object) throws Exception {
        System.out.println(">>> preHandle");
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println(">>> postHandle");
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println(">>> afterCompletion");
    }
}

4、拦截器配置

基于ant的通配符拦截所有/**。

基于code-base

@Configuration
@EnableWebMvc //启用spirng mvc java配置，相当于<mvc:annotation-driven/>
@ComponentScan(
        basePackages = {"cn.ycx.web.controller"},
        // 仅仅扫描
        includeFilters = {@Filter( type=FilterType.ANNOTATION, value={org.springframework.stereotype.Controller.class} )}
        )
public class ServletConfig extends WebMvcConfigurerAdapter {
    /**
     * 自定义拦截器
     * @return
     */
    @Bean
    public AuthenticationInterceptor handlerInterceptor() {
        return new AuthenticationInterceptor();
    }
    /**
     * 添加拦截器
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(handlerInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns(new String[] {
                        "/",
                        "/login",
                        "/resource/**"
                });
    }
}

基于xml-base

<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/**"/>
        <bean class="cn.ycx.web.interceptor.AuthenticationInterceptor" ></bean>
    </mvc:interceptor>
</mvc:interceptors>