SpringMVC框架六：拦截器

拦截器的概念就不介绍了：

SpringMVC中拦截器的执行规则：

一个小示例展示：

我搞两个拦截器：

第一个：

package org.dreamtech.springmvc.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 Interceptor1 implements HandlerInterceptor {

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("页面渲染后1");

    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("方法后1");

    }

    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("方法前1");
        return true;
    }

}

第二个：

package org.dreamtech.springmvc.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 Interceptor2 implements HandlerInterceptor {

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("页面渲染后2");

    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("方法后2");

    }

    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("方法前2");
        return true;
    }

}

然后把它配置到SpringMVC.xml中：

    <!-- 配置拦截器 -->
    <mvc:interceptors>
        <!-- 配置多个拦截器 -->
        <mvc:interceptor>
            <!-- 拦截所有 -->
            <mvc:mapping path="/**" />
            <!-- 自定义拦截器类 -->
            <bean class="org.dreamtech.springmvc.interceptor.Interceptor1" />
        </mvc:interceptor>
        <mvc:interceptor>
            <!-- 拦截所有 -->
            <mvc:mapping path="/**" />
            <!-- 自定义拦截器类 -->
            <bean class="org.dreamtech.springmvc.interceptor.Interceptor2s" />
        </mvc:interceptor>
    </mvc:interceptors>

执行之后：

然而我们如果把拦截器一的方法前不放行：

    @Override
    public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
        System.out.println("方法前1");
        return false;
    }

这时候，发现控制台只是打印了：方法前1

但是，我们如果把拦截器二的方法前不放行：

打印的却是：

到这里就可以看出SpringMVC的执行规则了：

为了方便，我借用某博主的图片:

文字解释：

preHandler按拦截器定义顺序调用，

postHandler按拦截器定义逆序调用，

afterCompletion按拦截器定义逆序调用，

postHandler在所有的拦截器返回成功时候才会调用，

afterCompletion在preHandler返回true才会调用

应用：

登录功能：只有登录才能查看其他信息

限制：在非登陆状态下无法访问该网站任何一处

随意写一个登录页面：

<body>
    <form action="${pageContext.request.contextPath }/login.action" method="post">
        用户名：<input type="text" name="username"> 
               <input type="submit" value="提交">
    </form>
</body>

只用一个拦截器：

    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <bean class="org.dreamtech.springmvc.interceptor.Interceptor2" />
        </mvc:interceptor>
    </mvc:interceptors>

拦截器：

package org.dreamtech.springmvc.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 Interceptor2 implements HandlerInterceptor {

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

    }

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

    }

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
        String requestURI = request.getRequestURI();
        /*
         * URI:/login.action
         * URL:http://xxx/xxx/login.action
         */
        if(!requestURI.contains("/login")){
            String username = (String) request.getSession().getAttribute("USER_SESSION");
            if(username==null){
                response.sendRedirect(request.getContextPath()+"/login.action");
                return false;
            }
        }
        return true;
    }

}

实现：

    @RequestMapping(value = "/login.action", method = RequestMethod.GET)
    public String login() {
        return "login";

    }

    @RequestMapping(value = "/login.action", method = RequestMethod.POST)
    public String login(String username, HttpSession httpSession) {
        httpSession.setAttribute("USER_SESSION", username);
        return "redirect:/item/itemlist.action";

    }

这里注意：我直接返回字符串：login是因为提前做了配置：

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

SpringMVC框架六：拦截器

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