SSM練習(三)：實現登錄功能

1. 登錄頁面

        大家可以在網上下載一個網站模板。例如百度一下bootstrap網站後臺模板，下載複製到自己的webapp目錄下。將登錄表單提交到userCheck，調用Controller層的方法來判斷用戶是否登錄。

<form action="/userCheck" method="get">

2. 登錄攔截器

        登錄攔截器的功能是實現將所有訪問該web應用下的資源的請求重定向到登錄頁面。 

2.1 寫一個登錄攔截器

        實現了HandlerInterceptor方法

package com.cnpc.web;

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

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


public class LoginInterceptor implements HandlerInterceptor{
   /**
    * 在請求之前執行
    * @param httpServletRequest
    * @param httpServletResponse
    * @param o
    * @return
    * @throws Exception
    */
   public boolean preHandle(HttpServletRequest httpServletRequest,
                      HttpServletResponse httpServletResponse,
                      Object o) throws Exception {
      String url=httpServletRequest.getRequestURL().toString();
      Object user=httpServletRequest.getSession().getAttribute("user");
      if (user!=null){
         return true;
      }
      if(httpServletRequest.getRequestURI().contains("login") || httpServletRequest.getRequestURI().contains("userCheck")
      || httpServletRequest.getRequestURI().contains("test")

      ) {
         return true;
      }

      httpServletResponse.sendRedirect(httpServletRequest.getContextPath()+"/pages/samples/login.jsp");
      return false;
   }

   
   public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse,
                     Object o, ModelAndView modelAndView) throws Exception {

   }

   public void afterCompletion(HttpServletRequest httpServletRequest,
                        HttpServletResponse httpServletResponse,
                        Object o, Exception e) throws Exception {

   }
}

2.2 在spring-web.xml中配置登錄攔截器

<mvc:interceptors>
    <mvc:interceptor>
        <!--<mvc:mapping path="/**"/>
            該路徑及其子路徑  -->
        <mvc:mapping path="/**"/>
        <mvc:exclude-mapping path="/**/*.css"/>
        <mvc:exclude-mapping path="/**/*.js"/>
        <mvc:exclude-mapping path="/**/*.png"/>
        <mvc:exclude-mapping path="/**/*.gif"/>
        <mvc:exclude-mapping path="/**/*.jpg"/>
        <mvc:exclude-mapping path="/**/*.jpeg"/>
        <mvc:exclude-mapping path="/pages/samples/login.html"/>
    </mvc:interceptor>
</mvc:interceptors>

2.3 小結

    問題1：無限重定向

        是否配置了<mvc:exclude-mapping path="/pages/samples/login.html"/>，該配置表示不攔截登錄的頁面。登錄攔截器的執行是這樣的，先檢查request域中是否存在用戶，存在就放行，不存在則攔截，重定向至登錄界面，如果不配置exclude-mapping的話，就會一直：檢查用戶不存在，跳轉至登錄，登錄又被攔截繼續檢查用戶，如此往復。

    問題2：用Postman等工具測試接口的時候，被攔截返回登錄頁面的html源碼

        這個問題也可以通過配置exclude-mapping來解決，我是這樣解決的，通過request.getUrl()獲取請求的url，我進行測試的時候url一般會包含一個test，然後在登錄攔截器的preHandle裏面：

if(httpServletRequest.getRequestURI().contains("test")

) {
   return true;
}

        這樣表示包含了test的請求就不會攔截了。

3. web層之UserController

3.1 UserController

@Controller
public class UserController {

    @Autowired
    private UserService userService;
    @RequestMapping("/login")
    public String login(){
        return "redirect:/pages/samples/login.jsp";
    }
    @RequestMapping("/userCheck")
    public String checkUser(String username, String password, HttpSession session){
        System.out.println("用戶:"+username+" "+password);
        String loginstate= userService.checkUserState(username,password);
        if (loginstate.equals("userNameNotExist")){
            return "redirect:login.action";
        }else if(loginstate.equals("passwordWrong")){
            return "redirect:login.action";
        }else {
            User user=new User();
            user.setUsername(username);
            user.setPassword(password);
            session.setAttribute("user",user);
            String url=userService.getUrlByName(username);
            return "redirect:"+url;
        }
    }
}

表單提交請求的URL是userCheck,通過調用userService裏的checkUserState檢查用戶是否存在，存在就往session中存入User對象，然後重定向到首頁。

4.Service層之UserService

自己添加一個字符串，再生成MD5碼，做一個簡單的加密，存入數據庫中。
@Service
public class UserServiceImpl implements UserService {

    private static final String sort="encryption:fantast1cyue";
    @Autowired
    private UserDao userDao;
    public String checkUserState(String username, String password) {

        User user = userDao.getUserByName(username);
        String passstr=password+sort;
        String md5 = DigestUtils.md5DigestAsHex(passstr.getBytes());
        if (user==null){
            return "userNameNotExist";
        }else if (!md5.equals(user.getPassword())){
            return "passwordWrong";
        }else {
            return "success";
        }
    }

    public  String getUrlByName(String username){
        String s = userDao.getUrlByName(username);
        return s;
    }
}

5.Dao層之UserDao

public interface UserDao {
     User getUserByName(String username);

     String getUrlByName(String username);
}

5.1 Mapper之UserDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.cnpc.dao.UserDao">
    <!--查詢用戶-->
    <select id="getUserByName"  resultType="com.cnpc.bean.User">
        select username,password from user where username = #{username}
    </select>

    <select id="getUrlByName" resultType="java.lang.String">
        select url from user where username = #{username}
    </select>

</mapper>