一、实体层

User.java

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Long id;
    private String userName;
    private String passwd;
    private String createDate;
}

Pager.java

package demo.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Pager {
    private Object data; //用于响应的数据
    private int pageTotle; //总条数
}

二、创建UserMapper.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="demo.dao.UserMapper">

</mapper>

三、通过ResultMap建立User实体和t_user表的映射关系

<?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="demo.dao.UserMapper">

<!-- 建立映射，将数据库中t_user表和java实体User建立关联 -->
<resultMap id="userResult" type="User">
    <result column="id" property="id"/>
    <result column="user_name" property="userName"/>
    <result column="passwd" property="passwd"/>
    <result column="create_date" property="createDate"/>
</resultMap>

</mapper>

四、在UserMapper中添加查询所有用户的方法

UserMapper.java

public interface UserMapper {
    public List<User> selectAll(int pageIndex, int pageSize);
}

UserMapper.xml (在UserMapper.xml中维护sql代码)

  <sql id="sql_temp">
        select id, user_name, passwd, create_date from t_useråå
    </sql>

    <select id="selectAll" resultMap="userResult">
        <include refid="sql_temp"></include> limit #{pageIndex}, #{pageSize}
    </select>

五、在IUserService中添加业务方法

IUserService接口

public interface IUserService {
   public Pager queryUserList(int pageIndex, int pageSize);
}

UserServiceImpl实现类 (注意: 在类前面加注解@Service 进行定位)

package demo.service.impl;

import demo.dao.UserMapper;
import demo.entity.User;
import demo.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service  //定位 UserServiceImpl
public class UserServiceImpl implements IUserService {

    @Autowired(required = false)
    private UserMapper userMapper;

    @Override
    public Pager queryUserList(int pageIndex, int pageSize) {
        List<User> list = userMapper.selectAll((pageIndex-1)*pageSize, pageSize);
        int count = userMapper.selectCount();
        return new Pager(list, count);
    }
}

五、在UserController中测试

package demo.controller;

import demo.dao.UserMapper;
import demo.entity.User;
import demo.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {

    //第1步: 创建IUserService对象
    @Autowired
    private IUserService userService;

    //第2步: 调用IUserService的方法
    @RequestMapping("/list")
    @CrossOrigin(origins = "*") //允许所有跨源请求
    public Pager findUserList(int pageIndex, int pageSize){
        return userService.queryUserList(pageIndex, pageSize);
    }

}

六、运行效果