拦截器及 Spring MVC 整合

一、实验介绍

1.1 实验内容

本节课程主要利用 Spring MVC 框架实现拦截器以及 Spring MVC 框架的整合。

1.2 实验知识点

• Spring MVC 框架
• 拦截器

1.3 实验环境

• JDK1.8
• Eclipse JavaEE

二、实验步骤

2.1 拦截器实现

在项目 hrms 的目录 src/main/java 下新建包 com.shiyanlou.interceptor，并在该包下新建类 LoginInterceptor，来验证用户是否登录，代码如下：

package com.shiyanlou.interceptor;

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

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class LoginInterceptor implements HandlerInterceptor {

    // 不拦截 "/login" 请求
    private static final String[] IGNORE_URI = { "/login" };

    @Override
    public void afterCompletion(HttpServletRequest arg0,
            HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {

    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1,
            Object arg2, ModelAndView arg3) throws Exception {

    }

    // 该方法将在 Controller 处理前进行调用
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
            Object handler) throws Exception {
        // flag 表示是否登录
        boolean flag = false;
        // 获取请求的 URL
        String url = request.getServletPath();
        for (String s : IGNORE_URI) {
            if (url.contains(s)) {
                flag = true;
                break;
            }
        }
        if (!flag) {
            // 获取 Session 并判断是否登录
            String username = (String) request.getSession().getAttribute(
                    "username");
            if (username == null) {
                request.setAttribute("message", "Please log in first!");
                // 如果未登录，进行拦截，跳转到登录页面
                request.getRequestDispatcher("/login.jsp")
                        .forward(request, response);
            } else {
                flag = true;
            }
        }
        return flag;
    }

}

2.2 spring-mvc.xml 配置文件

在目录 src/main/resources 下新建 Spring MVC 配置文件 spring-mvc.xml，添加如下代码：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
      http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context-4.2.xsd
      http://www.springframework.org/schema/mvc
     http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd">

    <!-- 自动扫描该包，Spring MVC 会将包下用 @Controller 注解的类注册为 Spring 的 controller -->
    <context:component-scan base-package="com.shiyanlou.controller" />
    <!-- 设置默认配置方案 -->
    <mvc:annotation-driven />
    <!-- 静态资源访问 -->
    <mvc:resources location="/" mapping="/**" />
    <!-- 视图解析器 -->
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/" />
        <property name="suffix" value=".jsp" />
    </bean>

    <bean id="multipartResolver"
        class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="maxUploadSize" value="3500000" />
        <property name="defaultEncoding" value="UTF-8" />
    </bean>
    <!-- 配置拦截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/*" />
            <bean class="com.shiyanlou.interceptor.LoginInterceptor" />
        </mvc:interceptor>
    </mvc:interceptors>
</beans>

2.3 配置 web.xml

修改项目 hrms 的 src->main->webapp->WEB-INF 目录下的 web.xml 内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>hrms</display-name>
    <!-- 配置 Spring 核心监听器 -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- 指定 Spring 的配置文件 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mybatis.xml</param-value>
    </context-param>

    <!-- 定义 Spring MVC 前端控制器 -->
    <servlet>
        <servlet-name>springMVC</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <!-- 为 DispatcherServlet 建立映射 -->
    <servlet-mapping>
        <servlet-name>springMVC</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <listener>
        <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class>
    </listener>

    <!-- 编码过滤器 -->
    <filter>
        <filter-name>encodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>encodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!-- 设置首页 -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
</web-app>

三、实验总结

到这里我们就实现了拦截器和 Spring MVC 的整合，项目的代码全部完成，下一节我们将对实现的系统进行运行测试。