mybatis plus中json格式实战

1.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.7.16</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>StudyMybatisPlus</artifactId><version>0.0.1-SNAPSHOT</version><name>StudyMybatisPlus</name><description>Demo project for Spring Boot</description><properties><java.version>11</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.5.1</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.21</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.12</version></dependency><dependency><groupId>org.reflections</groupId><artifactId>reflections</artifactId><version>0.9.10</version></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2.application.yml

#配置端口
server:port: 80spring:#配置数据源datasource:#配置数据源类型type: com.zaxxer.hikari.HikariDataSource#配置连接数据库的信息driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/mybatis_plus?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=CTT&allowPublicKeyRetrieval=trueusername: rootpassword: root#mybatis plus配置
mybatis-plus:configuration:log-impl: org.apache.ibatis.logging.stdout.StdOutImpl# 字段名和数据库中字段名一致map-underscore-to-camel-case: falseglobal-config:db-config:#配置mybatis plus 在更新时只更新非空和非NULL的字段update-strategy: not_empty# 实体名字和数据库表名一致table-underline: false# 需要转化为json的字段
map-field-scan-package: "com.example"

3.MapData.java

package com.example.studymybatisplus.anno;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MapData {
}

4.TypeConfig.java

package com.example.studymybatisplus.config;import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.autoconfigure.MybatisPlusProperties;
import com.baomidou.mybatisplus.autoconfigure.MybatisPlusPropertiesCustomizer;
import com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler;
import com.example.studymybatisplus.anno.MapData;
import org.reflections.Reflections;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;import java.lang.reflect.Field;
import java.util.HashSet;
import java.util.Set;/*** 注册需要转换为Map的处理器*/
@Configuration
public class TypeConfig implements MybatisPlusPropertiesCustomizer {@Value("${map-field-scan-package}")String packageName;@Overridepublic void customize(MybatisPlusProperties properties) {Reflections reflections = new Reflections(this.packageName);Set<Class<?>> typesAnnotatedWith = reflections.getTypesAnnotatedWith(TableName.class);Set<Class<?>> mapTypeSet = new HashSet<>();typesAnnotatedWith.forEach(clazz -> {Field[] fields = clazz.getDeclaredFields();for (Field field : fields) {field.setAccessible(true);if (field.getAnnotation(MapData.class) != null) {if(mapTypeSet.contains(field.getType())){continue;}mapTypeSet.add(field.getType());properties.getConfiguration().getTypeHandlerRegistry().register(field.getType(), JacksonTypeHandler.class);}}});}
}

5.UserMapper.java

package com.example.studymybatisplus.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.studymybatisplus.pojo.User;
import org.springframework.stereotype.Repository;import java.util.List;@Repository
public interface UserMapper extends BaseMapper<User> {/*** 测试自定义sql*/List<User> getUserList();
}

6.User.java

package com.example.studymybatisplus.pojo;import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.example.studymybatisplus.anno.MapData;
import lombok.Data;@Data
@TableName(autoResultMap = true)
public class User {@TableId(type = IdType.AUTO)private Long id;private String name = "";private Integer age = 0;@MapDataprivate UserInfo info = new UserInfo();
}

7.UserInfo.java

package com.example.studymybatisplus.pojo;import lombok.Data;import java.util.HashMap;
import java.util.Map;@Data
public class UserInfo {private String address="";private Map<Integer, Integer> map = new HashMap<>();private DataVo dataVo = new DataVo();private Integer aaa;
}

8.DataVo.java

package com.example.studymybatisplus.pojo;import lombok.Data;import java.util.HashMap;
import java.util.Map;@Data
public class DataVo {private Integer num;private Map<Integer, Integer> map2 = new HashMap<>();
}

9.主方法

package com.example.studymybatisplus;import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
@MapperScan("com.example.studymybatisplus.mapper")
public class StudyMybatisPlusApplication {public static void main(String[] args) {SpringApplication.run(StudyMybatisPlusApplication.class, args);}
}

10.UserMapper.xml // 测试自定义sql

<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.example.studymybatisplus.mapper.UserMapper"><select id="getUserList" resultType="com.example.studymybatisplus.pojo.User">SELECT id, name, age, infoFROM user</select>
</mapper>

可见，完全不需要ResultMap了，非常完美！！！

11.测试用例

package com.example.studymybatisplus;import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.example.studymybatisplus.mapper.UserMapper;
import com.example.studymybatisplus.pojo.User;
import com.example.studymybatisplus.pojo.UserInfo;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.List;
import java.util.Random;@SpringBootTest
class StudyMybatisPlusApplicationTests {@AutowiredUserMapper userMapper;@Testvoid contextLoads() {for (int i = 0; i < 10; i++) {User newUser = new User();newUser.setName("xx");newUser.setAge(30);newUser.getInfo().setAddress("北京 " + new Random().nextInt(10000));newUser.getInfo().getMap().put(1, 123);newUser.getInfo().getDataVo().setNum(222);newUser.getInfo().getDataVo().getMap2().put(666, 888);newUser.getInfo().getDataVo2().setNum(112222);int insert = userMapper.insert(newUser);System.out.println("insert:" + insert);System.out.println(newUser);// 测试QueryWrapperLambdaQueryWrapper<User> lambda = new QueryWrapper<User>().lambda();List<User> userList1 = userMapper.selectList(lambda);System.out.println(userList1);// 现在自定义sql也完全不需要ResultMap了List<User> userList2 = userMapper.getUserList();System.out.println(userList2);}}
}

9.输出

JDBC Connection [HikariProxyConnection@1111497601 wrapping com.mysql.cj.jdbc.ConnectionImpl@f1d1463] will not be managed by Spring
==>  Preparing: SELECT id,name,age,info FROM user
==> Parameters: 
<==    Columns: id, name, age, info
<==        Row: 1, xx, 30, <<BLOB>>
<==        Row: 2, xx, 30, <<BLOB>>
<==        Row: 3, xx, 30, <<BLOB>>
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@27502e5c]
[User(id=1, name=xx, age=30, info=UserInfo(address=北京2, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null)), User(id=2, name=xx, age=30, info=UserInfo(address=北京1, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null)), User(id=3, name=xx, age=30, info=UserInfo(address=北京 5542, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null))]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@12266084] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1839613624 wrapping com.mysql.cj.jdbc.ConnectionImpl@f1d1463] will not be managed by Spring
==>  Preparing: SELECT id, name, age, info FROM user
==> Parameters: 
<==    Columns: id, name, age, info
<==        Row: 1, xx, 30, <<BLOB>>
<==        Row: 2, xx, 30, <<BLOB>>
<==        Row: 3, xx, 30, <<BLOB>>
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@12266084]
[User(id=1, name=xx, age=30, info=UserInfo(address=北京2, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null)), User(id=2, name=xx, age=30, info=UserInfo(address=北京1, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null)), User(id=3, name=xx, age=30, info=UserInfo(address=北京 5542, map={1=123}, dataVo=DataVo(num=222, map2={666=888}), aaa=null))]
2023-10-22 00:14:07.258  INFO 10232 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2023-10-22 00:14:07.274  INFO 10232 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

可见，业务层可以愉快的使用Entity了，完全不需要关心是不是自定义sql，完美支持json，这样子mysql和mongodb就是一模一样了，只不过是复杂的类型多了一个自定义的@MapData注解！！

总结：

1.增加字段发现确实是可以的，删除字段就报错，所以这也符合游戏的目标也就是不能删和改字段名字。

2.注意在Entity中给默认值，因为我们用的都是包装类型，使用xdb的经验告诉我，所有的数据要给默认值，Map类型也要初始化一下。