Mybatis-Plus分页查询

Posted 2021-10-25 为BUG消得人憔悴

Mybatis-Plus分页查询

1、导入依赖

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.0.5</version>
</dependency>

2、编写配置文件.YML

spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/mybatis
    driver-class-name: com.mysql.jdbc.Driver
#配置日志
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

3、编写持久类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class user implements Serializable {
    @TableId(type = IdType.AUTO)
    private Long id;
    private String name;
    private Integer age;
    private String email;

    @Version//乐观锁注解
    private Integer version;

    @TableField(fill = FieldFill.INSERT)
    private Date createTime;

    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
}

4、编写mapper类

@Repository
public interface mapper extends BaseMapper <user> {

}

5、编写config配置类

//扫描mapper包
@MapperScan("com.xys.Mapper")
@EnableTransactionManagement
@Configuration//配置类
public class MybatisConfig {

    //注册乐观锁插件
    @Bean
    public OptimisticLockerInterceptor optimisticLockerInterceptor(){
        return new OptimisticLockerInterceptor();
    }

    //分页插件
    @Bean
    public PaginationInterceptor paginationInterceptor(){
        return new PaginationInterceptor();
    }
}

6、编写handle类

@Slf4j
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    //插入时的填充策略
    @Override
    public void insertFill(MetaObject metaObject) {
        log.info("start insert info....");
        this.setFieldValByName("createTime",new Date(),metaObject);
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }

    //更新时的填充策略
    @Override
    public void updateFill(MetaObject metaObject) {
        log.info("start update info....");
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }
}

7、分页查询

分页在网站使用的十分之多!

1、原始的limit进行分页

2、pageHelper第三方插件

3、MP其实也内置了分页插件!

//测试分页查询
@Test
void testPage(){
    Page<user> page=new Page<>(1,5);
    mapper.selectPage(page,null);
    page.getRecords().forEach(System.out::println);
}