SpringBoot 整合 MybatisPlus (项目的创建及简单的单表查询)

添加依赖

    <!--mybatis-plus的springboot支持-->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.0.5</version>
    </dependency>
    <!--mysql驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>

创建数据库和表

CREATE TABLE `user` (`id` BIGINT(20) not null AUTO_INCREMENT comment '主键ID',
    `name` VARCHAR(30) DEFAULT null comment '姓名',
    `age` int(11) DEFAULT null comment '年龄',
    `email` VARCHAR(50) DEFAULT null comment '邮箱',
    PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;
insert into user (id,name,age,email) VALUES ('1','Jone','18','test1@qq.com');

insert into user (id,name,age,email) VALUES ('2','Jack','20','test2@qq.com');

insert into user (id,name,age,email) VALUES ('3','Tom','28','test3@qq.com');

insert into user (id,name,age,email) VALUES ('4','Sandy','21','test4@qq.com');

insert into user (id,name,age,email) VALUES ('5','Billie','24','test5@qq.com');

配置 application.yml

spring:
  application:
    name: spring-boot-mybatis-plus
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/mysqlName?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL=false
    username: root
    password: root

创建pojo类

public class User {
    @TableId(value = "ID",type = IdType.AUTO)  //设置id为自增长
    private Long id;
    private String name;
    private Integer age;
    private String email;
		//( set,get,toString方法自行添加 )
}

创建 UserMapper接口

public interface UserMapper extends BaseMapper<User> {
}

注意：BaseMapper接口引入的包是

com.baomidou.mybatisplus.core.mapper.BaseMapper

编写 SpringBoot 启动类

@MapperScan("cn.mybatisplus.mapper")
@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class,args);
    }
}

@MapperScan("cn.mybatisplus.mapper"). 扫描 mapper 包

编写测试代码

@SpringBootTest
@RunWith(SpringRunner.class)
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testList(){
    List<User> users = this.userMapper.selectList(null);
    for (User user: users) {
        System.out.println(user);
    }
}
  @Test
public void testSelectById(){
    User user = this.userMapper.selectById(3L);   //根据id查数据
    System.out.println(user);
}
@Test
public void testSelectByLike(){
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.like("name","o");   //查询 name字段中包含‘o’的数据
    List<User> users = this.userMapper.selectList(wrapper);//返回值是一个list集合
    for (User u : users) {
        System.out.println(u);
    }
}
@Test
public void testSelectByLe(){
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    /**
     * eq : 等于
     * ne : 不等于
     * gt : 大于
     * ge : 大于等于
     * lt : 小于
     * le : 小于等于
     * 更多查看 https://mp.baomidou.com/guide/wrapper.html#abstractwrapper
     */
    wrapper.le("age","20");       //设置年龄小于等于20
    List<User> users = this.userMapper.selectList(wrapper);
    for (User u : users) {
        System.out.println(u);
    }
}
@Test
public void testSave() {
    User user = new User();
    user.setAge(25);
    user.setEmail("zhangsan@qq.com");
    user.setName("zhangsan");
    int count = this.userMapper.insert(user);
    System.out.println("新增数据成功  count ==> "+count);
}
@Test
public void testDelete(){
    this.userMapper.deleteById(6L);
    System.out.println("删除成功");
}
@Test
public void testUpdate(){
    User user = new User();
    user.setId(5L);
    user.setName("Lisi");
    int i = this.userMapper.updateById(user);
    System.out.println(" 有"+i+"条数据被修改");
}
}

分页查询

需要增加分页插件配置（这里就简单在启动类加 Bean）

@MapperScan("cn.itcast.mybatisplus.mapper")
@SpringBootApplication
public class MyApplication {
/*
 * 分页插件
 */
@Bean
public PaginationInterceptor paginationInterceptor(){
    return new PaginationInterceptor();
}
public static void main(String[] args) {
    SpringApplication.run(MyApplication.class,args);
}
}

测试

    @Test
    public void testSelectPage() {
        Page<User> page = new Page<>(2, 2);
        IPage<User> userIPage = this.userMapper.selectPage(page, null);
        System.out.println("总页数 ----> " + userIPage.getTotal());
        System.out.println("当前页数 ----> " + userIPage.getCurrent());
        System.out.println("当前每页显示数 ----> " + userIPage.getSize());
        List<User> records = userIPage.getRecords();
        for (User u: records) {
            System.out.println(u);
        }
    }

运行结果

总页数 ----> 5
当前页数 ----> 2
当前每页显示数 ----> 2
User(id=3, name=Tom, age=28, email=test3@qq.com)
User(id=4, name=Sandy, age=21, email=test4@qq.com)