基于SSM框架的 增 删 改 查

    **此篇代码是在SSM框架的下编写的增加，删除，修改，查询等操作，流程思路如下：**

** **1，在controller层创建UserController类；在service层创建Userservice接口，再创建一个实现类的包（impl）在包内创建一个UserServiceImpl的实现类，再在持久成（Dao层）创建UserDao接口；在resources中创建一个路径和UserDao接口一样的UserDao.xml文件，创建好的包结构如下：

     **2，开始代码编写（首先要清楚Controller层是实现后端与前端页面的跳转，Controller调用service层，service层调用Dao层，UserDao.xml文件实现sql语句的编写）**

（1），UserController中代码

package com.sm.controller;

import com.sm.domain.User;
import com.sm.service.UserService;
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.RequestParam;
import org.springframework.web.servlet.ModelAndView;
import java.util.List;

@Controller
public class UserController {
    @Autowired
    private UserService userService;
    @RequestMapping("/findAll")
    public String findAll(Model model){
        List<User> users = userService.findAll();
        System.out.println(users);
        model.addAttribute("users",users);
        return "list";
    }

//   增加数据 先跳转页面再保存数据
    @RequestMapping("/addjsp")
    public String addjsp(){
        return "add";
    }
    @RequestMapping("/saveUser")
    public String saveUser(User user){
        userService.saveUser(user);
        return "redirect:/findAll";
    }

//    修改数据 先用id查询
    @RequestMapping("/findUser")
    public ModelAndView findUser(Integer id){
//       转发到页面
        ModelAndView mv=new ModelAndView();
        User user=userService.findUser(id);
        mv.addObject(user);
        mv.setViewName("update");
        return mv;
    }
//    修改保存
    @RequestMapping("/updateUser")
    public String updateUser(User user){
        userService.updateUser(user);
        return "redirect:/findAll";
    }
//    按照id删除数据
    @RequestMapping("/delUser")
    public String delUser(Integer id){
        System.out.println(id);
        userService.delUser(id);
        return "redirect:/findAll";
    }

//    分页查询
    @RequestMapping("/findAllByPage")
   public ModelAndView findAllByPage(@RequestParam(name = "page",required = true,defaultValue = "1") Integer page,
                                    @RequestParam(name = "size",required = true,defaultValue = "3") Integer size){
       ModelAndView mv=new ModelAndView();
       List<User> users=userService.findAllByPage(page,size);
      //把查询到的数据交给分页模型处理
        PageInfo  pageInfo =new PageInfo(users);
       mv.addObject("pageInfo",pageInfo);
       mv.setViewName("list");
       return  mv;
    }
}

（2）UserService接口代码

package com.sm.service;

import com.sm.domain.User;
import java.util.List;

public interface UserService {
    List<User>findAll();
    void saveUser(User user);
    void delUser(Integer id);
    User findUser(Integer id);
    void updateUser(User user);
}

（3）UserServiceImpl类代码

package com.sm.service.impl;

import com.sm.dao.UserDao;
import com.sm.domain.User;
import com.sm.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service("userService")
public class UserServiceImpl implements UserService {
    @Autowired
    private UserDao userDao;
    @Override
    public List<User> findAll() {
        return userDao.findAll();
    }
    @Override
    public void saveUser(User user) {
        userDao.saveUser(user);
    }
    @Override
    public void delUser(Integer id) {
        userDao.delUser(id);
    }
    @Override
    public User findUser(Integer id) {
        return userDao.findUser(id);
    }
    @Override
    public void updateUser(User user) {
        userDao.updateUser(user);
    }

}

（4）UserDao代码

package com.sm.dao;

import com.sm.domain.User;
import org.springframework.stereotype.Component;
import java.util.List;

@Component
public interface UserDao {
    List<User> findAll();
    void saveUser(User user);
    void delUser(Integer id);
    void updateUser(User user);
    User findUser(Integer id);
}

当然不要忘了实体类（User）的创建

（5）UserDao.xml文件

<?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.sm.dao.UserDao">

<!--数据库总属性和User中属性不同时可以用 -->
<!--    <resultMap id="userMap" type="user">-->
<!--        <id  column="u_id" property="id"></id>-->
<!--        <result column="u_name" property="username"></result>-->
<!--        <result column="u_gender" property="usergender"></result>-->
<!--        <result column="u_address" property="useraddress"></result>-->
<!--    </resultMap>-->


    <select id="findAll" resultType="User">
        select * from user
    </select>


    <insert id="saveUser" parameterType="User">
        insert into user (username,usergender,useraddress)values (#{username},#{usergender},#{useraddress})
    </insert>


    <select id="findUser" parameterType="int" resultType="user">
        select * from user where id=#{id}
    </select>
    <update id="updateUser" parameterType="User">
        update user set username=#{username},usergender=#{usergender},useraddress=#{useraddress} where id=#{id}
    </update>


    <delete id="delUser" parameterType="int">
        delete from user where id=#{id}
    </delete>
</mapper>

3，前端页面

（1）index.jsp页面主要是用于跳转到主页面中主要代码

<a href="findAll">查询用户</a>

（2）核心页面

<table  class="table table-hover">
    <h3><a href="/addjsp"><button type="button" class="btn btn-warning">添加用户</button></a></h3>
<%--    表格设计--%>
    <tr>
        <th>id</th>
        <th>name</th>
        <th>gender</th>
        <th>address</th>
    </tr>

<%--    获取值--%>
    <c:forEach items="${users}" var="user">
        <tr>
            <td>${user.id}</td>
            <td>${user.username}</td>
            <td>${user.usergender}</td>
            <td>${user.useraddress}</td>
            <td>
                <button type="button" class="btn btn-warning" onclick="updateUser('${user.id}')">编辑</button>
                <button type="button" class="btn btn-danger" onclick="delUser('${user.id}')" >删除</button>
            </td>
        </tr>
    </c:forEach>
    <tr>
        <td>
            <button type="button" class="btn btn-danger" >全删除</button>
        </td>
    </tr>
</table>
<script>
    <%--    删除的方法--%>
        function delUser(id){
            var flag=confirm("确定删除？");
            if(flag){
                location.href="delUser?id="+id;
            }
        }
        function  updateUser(id) {
            location.href="findUser?id="+id;
        }

</script>

最终页面展示：