mybatis-plus improves efficiency of CRUD operations

1. Auto-fill at code level

1. Add @TableField annotation to the entity class

The premise is that there are corresponding fields in your database, and there is no automatic filling setting, and then add @TableField annotations to the attributes that need to be filled

package com.hzxy.mybatisplus.model;


import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    
    

    private Long id;
    private String name;
    private Integer age;
    private String email;

    //  字段添加填充
    @TableField(fill = FieldFill.INSERT)
    private Date CreateTime;

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

2. Write a custom processor

We need to write a custom processor to handle the filling content

package com.hzxy.mybatisplus.handler;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;

import java.util.Date;

@Slf4j
@Component      //把处理器加到IOC容器中
public class MyMetaObjectHandler implements MetaObjectHandler {
    
    

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

3. Testing

    @Test
    public void testInsert(){
    
    
        User user = new User();
        user.setName("Ye");
        user.setAge(18);
        user.setEmail("[email protected]");
        int result = userMapper.insert(user);
        System.out.println(result);
        System.out.println(user);
    }

    @Test
    public void testUpdate(){
    
    
        User user = new User();
        user.setId(1364545190177611777L);
        user.setName("Ye");
        user.setAge(20);
        user.setEmail("[email protected]");
        int result = userMapper.updateById(user);
        System.out.println(result);
        System.out.println(user);
    }
}

result:

2. Add SQL statement log

Add in the configuration

### 配置日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

result:

3. Add optimistic lock plugin

1. Add @Version annotation to the entity class

Note that there must be corresponding fields in the database

package com.hzxy.mybatisplus.model;


import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.Version;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    
    

    private Long id;
    private String name;
    private Integer age;
    private String email;

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

    //  字段添加填充
    @TableField(fill = FieldFill.INSERT)
    private Date CreateTime;

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

2. Add configuration configuration class

We create a new configuration class and release the annotation of scanning Mapper to this class

package com.hzxy.mybatisplus.config;


import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;

// 扫描我们的 Mapper 文件夹
@MapperScan("com.hzxy.mybatisplus.mapper")
@EnableTransactionManagement
@Configuration  //配置类
public class MybatisPlusConfig {
    
    

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

3. Testing

First test

    @Test
    public void testOptimisticLocker(){
    
    
        // 1. 查询用户信息
        User user = userMapper.selectById(1L);
        // 2. 修改用户信息
        user.setName("ybg");
        user.setEmail("[email protected]");
        // 3. 执行更新操作
        userMapper.updateById(user);
    }

result:

Second test

    @Test
    public void testOptimisticLocker2(){
    
    
        // 1. 查询用户信息
        User user = userMapper.selectById(1L);
        // 2. 修改用户信息
        user.setName("ybg");
        user.setEmail("[email protected]");
        // 3. 执行更新操作

        // 1. 查询用户信息
        User user1 = userMapper.selectById(1L);
        // 2. 修改用户信息
        user.setName("dzy");
        user.setEmail("[email protected]");
        // 3. 执行更新操作
        userMapper.updateById(user1);


        userMapper.updateById(user);
    }

result:

Note: The version is 4 because I executed it twice, the second screenshot!

4. Three query methods

    // 通过id查询
    @Test
    public void testSelectById(){
    
    
        User user = userMapper.selectById(1L);
        System.out.println(user);
    }

    // 批量查询
    @Test
    public void testSelectByBatchId(){
    
    
        List<User> users = userMapper.selectBatchIds(Arrays.asList(1,2,3));
        users.forEach(System.out::println);
    }

    // 条件查询之一map查询
    @Test
    public void testSelectByMap(){
    
    
        HashMap<String,Object> map = new HashMap<>();
        map.put("name","Ye");
        List<User> users = userMapper.selectByMap(map);

        users.forEach(System.out::println);
    }

The result of the last query:

5. Paging query

1. Add the following code to the configuration class

    // 分页拦截器
    @Bean
    public  PaginationInterceptor paginationInnerInterceptor() {
    
    
        return new PaginationInterceptor();
    }

2. Testing

    @Test
    public void testPaginationInterceptor(){
    
    
        // 参数一: 当前页
        // 参数二: 页面大小
        Page<User> page = new Page<>(2,2);
        userMapper.selectPage(page,null);
        page.getRecords().forEach(System.out::println);
    }

result:

6. Three deletion methods

    // 通过id删除
    @Test
    public void testDeleteById(){
    
    
        userMapper.deleteById(1L);
    }

    // 批量删除
    @Test
    public void testDeleteByBatchId(){
    
    
        userMapper.deleteBatchIds(Arrays.asList(1,2,3));
    }

    // 条件删除之一map删除
    @Test
    public void testDeleteByMap(){
    
    
        HashMap<String,Object> map = new HashMap<>();
        map.put("name","Ye");
        userMapper.deleteByMap(map);

    }

The last deleted result:

7, logical deletion

1. Add @TableLogic annotation to the entity class

Note that there must be corresponding fields in the database

    @TableLogic  //逻辑删除
    private Integer deleted;

2. Add configuration

Configuration file

### 配置逻辑删除
mybatis-plus.global-config.db-config.logic-delete-value=1
mybatis-plus.global-config.db-config.logic-not-delete-value=0

Configuration class

    // 逻辑删除组件
    @Bean
    public ISqlInjector sqlInjector(){
    
    
        return new LogicSqlInjector();
    }

3. Testing

Although it is still a deletion method, it actually uses logical deletion

    // 通过id删除
    @Test
    public void testDeleteById(){
    
    
        userMapper.deleteById(1L);
    }

Result:


Test the query again

    // 通过id查询
    @Test
    public void testSelectById(){
    
    
        User user = userMapper.selectById(1L);
        System.out.println(user);
    }

Result: After the


logical deletion, the query is not available, but the database still has this data.