springmvc+jsp 拦截器下如何设置欢迎页面

0.需求

如何让用户在浏览器地址栏键入[http://XXX.XXX.XX.XX:端口号/应用名/]以后自动跳转到系统的登录界面

1.web.xml

1.1 注意welcome-file-list的配置，将welcome-file赋值为"/"

1.2 springmvc 的 dispatcherServlet的url-pattern是"/"

<?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_2_5.xsd"
    id="WebApp_ID" version="2.5">
    <display-name>leslie</display-name>
    <welcome-file-list>
        <welcome-file>/</welcome-file>
    </welcome-file-list>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mybatis.xml,/WEB-INF/leslie-dispatcher-servlet.xml,/WEB-INF/applicationContext-timertask.xml
    </param-value>
    </context-param>
    <!-- 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>
    </filter>
    <filter-mapping>
        <filter-name>encodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <!-- Spring监听器 -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!-- 防止Spring内存溢出监听器 -->
    <listener>
        <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class>
    </listener>

    <servlet>
        <servlet-name>leslie-dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>leslie-dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <context-param>
        <param-name>logbackConfigLocation</param-name>
        <param-value>classpath:logback.xml</param-value>
    </context-param>
    <listener>
        <listener-class>ch.qos.logback.ext.spring.web.LogbackConfigListener</listener-class>
    </listener>

    <context-param>
        <param-name>spring.profiles.active</param-name>
        <param-value>dev</param-value>
    </context-param>
    <context-param>
        <param-name>spring.profiles.default</param-name>
        <param-value>dev</param-value>
    </context-param>
    <context-param>
        <param-name>spring.liveBeansView.mbeanDomain</param-name>
        <param-value>dev</param-value>
    </context-param>

</web-app>

2.dispatcherServlet配置文件

2.1 注意我配置了一个判断用户是否登录的拦截器

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/task
        http://www.springframework.org/schema/task/spring-task-3.0.xsd">

    <context:component-scan base-package="com.leslie" />

    <mvc:annotation-driven />

    <!--url拦截器，对指定的Url进行拦截，判断Session中是否存在用户信息，防止用户通过直接输入url的方式越级访问 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <bean class="com.leslie.interceptor.UserLoginInterceptor" />
        </mvc:interceptor>
    </mvc:interceptors>

    <!--国际化property文件 -->
    <!-- <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
        <property name="basenames"> <list> <value>classpath:/messages/messages</value>
        </list> </property> <property name="useCodeAsDefaultMessage" value="true"
        /> </bean> -->

    <!--避免IE执行AJAX时，返回JSON出现下载文件 -->
    <bean id="mappingJacksonHttpMessageConverter"
        class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
        <property name="supportedMediaTypes">
            <list>
                <value>text/html;charset=UTF-8</value>
            </list>
        </property>
    </bean>

    <!-- 启动SpringMVC的注解功能，完成请求和注解POJO的映射 -->
    <bean
        class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="messageConverters">
            <list>
                <ref bean="mappingJacksonHttpMessageConverter" /> <!-- JSON转换器 -->
            </list>
        </property>
    </bean>
    <!-- 定义跳转的文件的前后缀 ，视图模式配置 -->
    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>

    <!-- 配置文件上传，如果没有使用文件上传可以不用配置，当然如果不配，那么配置文件中也不必引入上传组件包 -->
    <bean id="multipartResolver"
        class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- 默认编码 -->
        <property name="defaultEncoding" value="utf-8" />
        <!-- 文件大小最大值 -->
        <property name="maxUploadSize" value="10485760000" />
        <!-- 内存中的最大值 -->
        <property name="maxInMemorySize" value="40960" />
    </bean>

</beans>

2.2 拦截器的实现代码

2.2.1 字符串数组IGNORE_URI定义了拦截器不拦截的uri，包括用户登录界面以及check用户登录信息两个逻辑是不拦截的。

preHandle方法在执行controller之前被执行，主要的逻辑是首先看当前url是不是在IGNORE_URI中定义的，

如果是就放行，返回true。如果不是，就从session里取用户登录信息，如果取到了用户对象则视为用户已经登录，那么放行，返回true。否则，视为用户未登录，不放行，返回false。

2.2.2 我们的目的是让拦截器为"/"放行，但我们不能将"/"配置到IGNORE_URI里，因为"/"表示任意的url-pattern，这样拦截器势必会对所有的url放行，失去了

拦截的意义。所以就有了requestUrl.endsWith(applicationName)这个逻辑，也就是手动判断当前url是不是[http://XXX.XXX.XX.XX:端口号/应用名/]风格的，如果是就放行。

package com.leslie.interceptor;

import java.io.File;

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

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import com.leslie.controller.SJLoginController;
import com.leslie.model.User;

/**
 * 登录拦截器
 *
 *
 */
@Interceptor
public class UserLoginInterceptor extends HandlerInterceptorAdapter {
    private static final String[] IGNORE_URI = { "/loginPage", "/checkLogin", "/hello" };

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        String applicationName = "/"
                + request.getContextPath().split("/")[request.getContextPath().split("/").length - 1] + "/";
        String requestUrl = request.getRequestURL().toString();
        if (requestUrl.endsWith(applicationName)) {
            return true;
        }
        boolean flag = false;
        String url = request.getRequestURL().toString();
        for (String s : IGNORE_URI) {
            if (url.contains(s)) {
                flag = true;
                break;
            }
        }
        if (!flag) {
            User user = SJLoginController.getLoginUser(request);
            if (user != null) {
                // List<String> urls =
                // SJLoginController.getUserRoleUrls(request);
                // if(urls.contains(url)){
                // flag = true;
                // }
                flag = true;
            }
        }
        return flag;
    }

}

3.为欢迎页面单独分配一个controller

3.1 使用forward将页面跳转到兄弟controller，在这里是用户登录controller的打开登录页面url

package com.leslie.util;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class SJWelcomeController {
    @RequestMapping("/")
    public String welcome(){
        return "forward:/login/loginPage";
    }
}