创建实体类和数据库建立映射关系

package com.xbb.mybatisplus.tutorial.entity;

public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + ", email=" + email + "]";
    }
    
}

建立Mapper接口用于访问数据库

package com.xbb.mybatisplus.tutorial.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.xbb.mybatisplus.tutorial.entity.User;

public interface UserMapper extends BaseMapper<User> {

    
    
}

在src/test/java下创建com.xbb.mybatisplus.tutorial.MybatisPlusTest

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package com.xbb.mybatisplus.tutorial;

import java.util.List;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.xbb.mybatisplus.tutorial.entity.User;
import com.xbb.mybatisplus.tutorial.mapper.UserMapper;

@SpringBootTest
class MybatisPlusTest {

    @Autowired
    private UserMapper userMapper;

    /**
     * 保存
     */
    @Test
    public void save() {
        User user = new User();
        user.setId(6l);
        user.setAge(18);
        user.setEmail("zhubajie@163.com");
        user.setName("zhubajie");
        userMapper.insert(user);
    }
    
    /**
     * 全表字段更新
     */
    @Test
    public void update() {
        User user = new User();
        user.setId(6l);
        user.setAge(19);
        user.setEmail("sunwukong@163.com");
        user.setName("sunwukong");
        userMapper.updateById(user);
    }
    
    /**
     * 只更新特定字段
     */
    @Test
    public void updateSelected() {
        User user = new User();
        user.setId(6l);
        user.setAge(25);
        userMapper.updateById(user);
    }

    /**
     * 删除
     */
    @Test
    public void delete() {
        userMapper.deleteById(6l);
    }
    
    /**
     * 查询
     */
    @Test
    public void selectList() {
        QueryWrapper<User> qw = new QueryWrapper<>();
        List<User> selectList = userMapper.selectList(qw);
        selectList.forEach(user->{
            System.out.println(user);
        });
    }
    
    /**
     * 等值条件查询
     */
    @Test
    public void listByEq() {
        QueryWrapper<User> qw = new QueryWrapper<>();
        qw.eq("name", "Jone");
        List<User> selectList = userMapper.selectList(qw);
        selectList.forEach(user->{
            System.out.println(user);
        });
    }
    
    /**
     * 通过id查找某一条记录
     */
    @Test
    public void listById() {
        User user = userMapper.selectById(3l);
        System.out.println(user);
    }
    
    /**
     * 分页查询
     */
    @Test
    public void page() {
        QueryWrapper<User> qw = new QueryWrapper<>();
        Page<User> page = new Page<>();
        page.setSize(2l);
        page.setCurrent(1l);
        Page<User>  pageResult = userMapper.selectPage(page, qw);
        System.out.println("总页数:" + pageResult.getPages());
        System.out.println("每页显示的最大记录数:"+pageResult.getSize());
        System.out.println("当前页码:" + pageResult.getCurrent());
        System.out.println("符合条件的总记录数:" + pageResult.getTotal());
        pageResult.getRecords().forEach(user -> {
            System.out.println(user);
        });
    }
    
}