MyBatis-plus 新增时List转String 查询时String转list

1. 需求说明

项目为：SpringBoot+MyBatisPlus

采用实体类接受参数，有一个参数为List ，对应的数据库字段为nvachar,要求新增时将List序列化为String插入数据库中，查询时将String转成

List

2.具体操作

1. 新增自定义的typeHandler,继承BaseTypeHandler，具体代码如下：

package com.zjjg.dlbp.config;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.springblade.core.tool.utils.ObjectUtil;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * List<Integer> ==>  string
 * @Date 2022-10-08
 */
public class ListToStringHandle extends BaseTypeHandler<List> {


    @Override
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, List list, JdbcType jdbcType) throws SQLException {
        if (ObjectUtil.isNotEmpty(list)){
            preparedStatement.setString(i, JSON.toJSONString(list));
        }

    }

    @Override
    public List getNullableResult(ResultSet resultSet, String s) throws SQLException {
        String result = resultSet.getString(s);
        return result ==null? new ArrayList<>():JSONArray.parseArray(result);
    }

    @Override
    public List getNullableResult(ResultSet resultSet, int i) throws SQLException {
        String result = resultSet.getString(i);
        return result ==null? new ArrayList<>():JSONArray.parseArray(result);
    }

    @Override
    public List getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        String result = callableStatement.getString(i);
        return result ==null? new ArrayList<>():JSONArray.parseArray(result);
    }
}

2. 在数据库对应实体类字段上增加注解

       @TableField(jdbcType = JdbcType.VARCHAR,typeHandler = ListToStringHandle.class)
       private List<Integer> protectiveFacility;
   
       @TableField(jdbcType = JdbcType.VARCHAR,typeHandler = ListToStringHandle.class)
       private List<Integer> drainageFacility;
   

3. 在mapper.xml中 对应字段上添加typeHandler

    <result column="drainage_facility" property="drainageFacility" typeHandler="com.zjjg.dlbp.config.ListToStringHandle"/>
    <result column="protective_facility" property="protectiveFacility" typeHandler="com.zjjg.dlbp.config.ListToStringHandle"/>
   

4. 在application.yml文件中，增加 type-handlers-package配置，设置typeHandle所在包位置

   mybatis-plus:
   	type-handlers-package: com.app.config