springmvc拦截器登录验证示例

一开始,学了拦截器与过滤器,咋一看两者有点像,实际上两者有很大的不同。就用拦截器和过滤器分别做了登录验证试验,这次先说拦截器。下面是自己实践的一个实例:

在spring-mvc.xml中配置拦截器:

<mvc:interceptors>
  <mvc:interceptor> 
   <mvc:mapping path="/user/*"/> 
<!-- 定义在mvc:interceptor下面的表示是对特定的请求才进行拦截的 -->
   <bean class="com.wyb.interceptor.LoginInterceptor"/> 
  </mvc:interceptor>  
 </mvc:interceptors>

如上所示,这里配置了LoginIntercepter,为了简单起见,该过滤器只拦截了URL为"/user/*"的请求。

要拦截的请求对应控制器如下:

import java.util.ArrayList;
import java.util.List;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.wyb.domain.User;
import com.wyb.service.IUserService;
import com.wyb.service.impl.UserServiceImpl;

@Controller 
@RequestMapping("/user") 
public class UserController { 
 
   private static final Logger LOG=Logger.getLogger(UserController.class);

   @Autowired 
   private IUserService userService; 
  

 @RequestMapping("/showAllUser")
 public String showAllUser(Model m){
  List<User> userlist=new ArrayList<User>(); 
  userlist=userService.findAllUser();
  for(User user :userlist){
   System.out.println(user.getUserName());
  }  
  return "/jsp/showAllUser";
  
 }
}

这里的showAllUser()方法是为了输出所有的用户,为了表明执行了方法,将所有用户在后台打印,URL为:http://localhost:8080/TestSSM/user/showAllUser,可见该URL肯定会被LoginIntercepter拦截。

测试页面showAllUser.jsp如下:

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>show All User</title>
</head>
<body>
 this is showAllUser Page!!!
</body>
</html>

LoginIntercepter如下:

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

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

import com.wyb.domain.User;

public class LoginInterceptor implements HandlerInterceptor{

 @Override
 public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
   throws Exception {
  System.out.println("this is afterCompletion of LoginInterceptor");
  
 }

 @Override
 public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
   throws Exception {
  System.out.println("this is postHandle of LoginInterceptor");
  
 }

 @Override
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
  // TODO Auto-generated method stub
  System.out.println("this is preHandle of LoginInterceptor");
  HttpSession session=request.getSession();
  User user=(User)session.getAttribute("user");
  if(user==null){
   System.out.println("no user in LoginInterceptor!!!");
   request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);

  } 
  //返回true代表继续往下执行
  return true;
 }

}

 这里我犯了一个错误,聪明的小伙伴也许已经看出来了,如果按照上面的代码,当我们访问:http://localhost:8080/TestSSM/user/showAllUser结果如下:

咋一看,成功拦截了,输入用户名信息,正常跳转到主页,再次进入http://localhost:8080/TestSSM/user/showAllUser如下:

页面正常输出,已经记录了session,不会被再次拦截,看似成功了,可是看看后台输出:

有没有发现,我们执行了两次showAllUser()方法,可见第一次访问虽然被拦截器拦截了下来进入登录页面,但后台已经悄悄执行了showAllUser()。为什么呢?我们回头再看看LoginIntercepter.java,尤其是preHandle()方法:

@Override
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
  // TODO Auto-generated method stub
  System.out.println("this is preHandle of LoginInterceptor");
  HttpSession session=request.getSession();
  User user=(User)session.getAttribute("user");
  if(user==null){
   System.out.println("no user in LoginInterceptor!!!");
   request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);

  } 
  //返回true代表继续往下执行
  return true;
 }

在判断user为空后,虽然执行了页面跳转,但是程序还是会继续执行,最后返回true,返回true意味着,被拦截的业务逻辑可以继续往下执行,因此,虽然表面上被拦截了,但从本质上来说并没有拦截到。因此需要修改如下:

@Override
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
  // TODO Auto-generated method stub
  System.out.println("this is preHandle of LoginInterceptor");
  HttpSession session=request.getSession();
  User user=(User)session.getAttribute("user");
  if(user==null){
   System.out.println("no user in LoginInterceptor!!!");
   request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
   //本次访问被拦截,业务逻辑不继续执行
   return false;
  } 
  //返回true代表继续往下执行
  return true;
 }

user为空,跳转后,返回false,就不会执行被拦截的业务逻辑了,修改后后台输出如下:

现在后台正常输出,且session保存了user信息后,才能执行showAllUser()方法,大功告成!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持编程小技巧。

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