Mybatis-Plus自定义集合类型的类型处理器详解

@Slf4j
@MappedJdbcTypes(value = JdbcType.VARCHAR)
public class FastJsonArrayTypeHandler extends AbstractJsonTypeHandler<List<?>> { 
    private Class<?> type; 
    public FastJsonArrayTypeHandler(Class<?> type) {
        if (log.isTraceEnabled()) {
            log.trace("FastjsonTypeHandler(" + type + ")");
        }
        Assert.notNull(type, "Type argument cannot be null");
        this.type = type;
    }
 
    @Override
    protected List<?> parse(String json) {
        return JSON.parseArray(json, type);// 注意不要使用parseObject方法
    }
 
    @Override
    protected String toJson(List<?> obj) {
        return JSON.toJSONString(obj, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty);
    } 
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="a.b.dao.DemoDao">
    <resultMap type="a.b.entity.DemoEntity" id="demoMap">
        <result property="DemoInfo" column="demo_info" javaType="a.b.xx.DiseaseInfo" typeHandler="a.b.handler.FastJsonArrayTypeHandler"/>
    </resultMap>
</mapper>

@Mapper
public interface DemoDao extends BaseMapper<DemoEntity> {
    @Select("select * from demo where demo_id = #{demoId}")
    @ResultMap(value = "demoMap")
    List<DemoEntity> selectListByPlanId(Long demoId);
}

@Data
@TableName(value = "demo", resultMap = "demoMap")
public class DemoEntity implements Serializable {
    private static final long serialVersionUID = -1L;
 
    
    @TableId
    private Long id;
    private Long demoId
    
    private List<DemoInfo> demoInfo;
}

@Slf4j
@MappedJdbcTypes(value = JdbcType.VARCHAR)
public class FastJsonArrayTypeHandler<T> extends AbstractJsonTypeHandler<Object> { 
    private TypeReference<List<T>> type; 
    public FastJsonArrayTypeHandler(TypeReference<List<T>> type) {
        this.type = type;
    }
 
    @Override
    protected Object parse(String json) {
        return JSON.parseObject(json, type);
    }
 
    @Override
    protected String toJson(Object obj) {
        return JSON.toJSONString(obj, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty);
    } 
}

@Component
public class InitConfig implements CommandLineRunner {
    public static final com.alibaba.fastjson.TypeReference<List<DemoInfo>> F_DEMO_INFO = new com.alibaba.fastjson.TypeReference<List<DemoInfo>>() {
    };
    public static final TypeReference<List<DemoInfo>> M_DEMO_INFO = new TypeReference<List<DemoInfo>>() {
    };
    // mp自动装配时注入的factory，可用于获取mybatis的配置属性，这里用来获取类型处理器的注册器
    private final SqlSessionFactory factory;
 
    public InitConfig(SqlSessionFactory factory) {
        this.factory = factory;
    }
 
    
    @SuppressWarnings("all")
    @Override
    public void run(String... args) throws Exception {
        TypeHandlerRegistry typeHandlerRegistry = factory.getConfiguration().getTypeHandlerRegistry();
        typeHandlerRegistry.register(M_DEMO_INFO, new FastJsonArrayTypeHandler(F_DEMO_INFO));
    }
}