Mybatis-Plus学习1-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_41444888/article/details/131423299

文章展示了如何在Java项目中使用MyBatis-Plus和Lombok进行数据库的增删改查操作。通过添加mybatis-plus-boot-starter和lombok的依赖，利用Lombok的注解简化实体类的构建，然后定义UserMapper接口继承BaseMapper，实现对User表的操作。在测试类中，演示了insert、deleteByMap、updateById和selectList等方法的使用。

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mybatis-plus需要两个依赖，一个lombok，一个mybatis-plus

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.1</version>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

package com.learn.mybatisplus.pojo;
import lombok.*;

//lombok快速创建实体类
//@Data=无参构造+getter+setter+hash+toString
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@EqualsAndHashCode

@Data
@TableName("user")
public class User {

    private long id;

    private Integer age;

    private String name;

    private String email;

}

mapper继承BaseMapper即可

basemapper中封装了很多方法，如userMapper.selectList

// 标识为持久层组件
@Repository
public interface UserMapper extends BaseMapper<User> {

}

@SpringBootTest
public class MyBatisPlusTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelctList() {
        // 通过条件构造器查询一个List集合，若没有条件则设置wrapper条件为null
        List<User> list = userMapper.selectList(null);
        list.forEach(System.out::println);
    }
}

//配置文件中配置在日志中输出mybatis-plus生成的sql
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

通过userMapper的方法实现增删改查

    @Test
    public void testInsert() {
        User user = new User();
        user.setAge(24);
        user.setEmail("wxs@qq.cn");
        user.setName("王xs");
        int result = userMapper.insert(user);
        System.out.println("result = " + result);
        System.out.println("id = " + user.getId());
    }


    @Test
    public void testDelete() {
        //int result = userMapper.deleteById(1674710493506195458L);
        //System.out.println("result = " + result);

        Map<String, Object> map = new HashMap<>();
        map.put("name", "张三");
        map.put("age",23);
        int result = userMapper.deleteByMap(map);
        //执行的sql：DELETE FROM user WHERE name = ? AND age = ?
        System.out.println(result);

        //通过idList批量删除
        List<Long> list = Arrays.asList(1L, 2L, 3L);
        int result = userMapper.deleteBatchIds(list);
        System.out.println("result = " + result);


    @Test
    public void testUpdate() {
        User user = new User();
        user.setId(4L);
        user.setName("李四");
        user.setEmail("lisi@qq.com");
        int result = userMapper.updateById(user);
        //执行的sql：UPDATE user SET name=?, email=? WHERE id=?
        System.out.println(result);
    }

    @Test
    public void testSelect() {
        User user = userMapper.selectById(1L);
        System.out.println(user);

        List<Long> list = Arrays.asList(1L, 2L, 3L);
        List<User> users = userMapper.selectBatchIds(list);
        users.forEach(System.out::println);

        Map<String, Object> map = new HashMap<>();
        map.put("name", "Jack");
        map.put("age", 20);
        List<User> users = userMapper.selectByMap(map);
        users.forEach(System.out::println);

        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }