Mybatis中，映射mysql中的JSON字段

数据库mysql中的的某一个字段，存放的是一个List 的集合，需要将字段对应到entity的某一个参数上，mapper.xml中使用
的方式直接进行字段映射时，会出现java.lang.IllegalStateException: No typehandler found for property abnormalEigenList，具体的错误：

java.lang.IllegalStateException: No typehandler found for property abnormalEigenListat org.apache.ibatis.mapping.ResultMapping$Builder.validate(ResultMapping.java:151)at org.apache.ibatis.mapping.ResultMapping$Builder.build(ResultMapping.java:140)at org.apache.ibatis.builder.MapperBuilderAssistant.buildResultMapping(MapperBuilderAssistant.java:446)at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildResultMappingFromContext(XMLMapperBuilder.java:393)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:280)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:254)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:246)at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:119)

这时，我们需要定义一个类，对该json字符串进行转义：

import com.alibaba.fastjson.JSONException;import com.alibaba.fastjson.JSONObject;import com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler;import java.util.ArrayList;import java.util.List;public class JsonHandler extends JacksonTypeHandler {    public JsonHandler (Class<?> type) {        super(type);    }    @Override    protected List<String> parse(String json) {        List<String> jsons = new ArrayList<>();        try {            jsons = JSONObject.parseArray(json, String.class);        } catch (JSONException e) {            jsons.add(JSONObject.parseObject(json, String.class));        }        return  jsons;    }}

在mapper.xml中，需要在字段映射时加入typeHandler，具体：

来源地址：https://blog.csdn.net/github_38924695/article/details/131501276