业务扩展字段在PostgreSQL数据库中经常会使用json格式的数据来存储,然而mybatis默认是没有实现json类型字段对应的TypeHandler,所以一般我们需要自定义mybatis的TypeHandler。

如下是mybatis中json类型字段对应的TypeHandler的一个简单实现:

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedTypes;
import org.postgresql.util.PGobject; import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException; @MappedTypes({Object.class})
public class JsonTypeHandler extends BaseTypeHandler<Object> { @Override
public void setNonNullParameter(PreparedStatement preparedStatement, int i, Object o, JdbcType jdbcType) throws
SQLException {
     PGobject jsonObject = new PGobject(); 
jsonObject.setType("json");
jsonObject.setValue(JsonUtil.toJsonString(o));
preparedStatement.setObject(i, jsonObject); } @Override
public Object getNullableResult(ResultSet resultSet, String s) throws SQLException {
return JsonUtil.fromJson(resultSet.getString(s), Object.class);
} @Override
public Object getNullableResult(ResultSet resultSet, int i) throws SQLException {
return JsonUtil.fromJson(resultSet.getString(i), Object.class);
} @Override
public Object getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
return JsonUtil.fromJson(callableStatement.getString(i), Object.class);
}
}

除了编写TypeHandler外,还需要在xml映射文件中做如下配置:

    <resultMap id="BaseResultMap" type="com.test.entity.EventLog">
<id column="uuid" jdbcType="VARCHAR" property="uuid"/>
<result column="payload" jdbcType="OTHER" property="payload" typeHandler="com.test.dao.typehandler.JsonTypeHandler"/>
</resultMap>
    <insert id="insert" parameterType="com.test.entity.EventLog">
insert into "test".event_log (uuid,payload)
values (#{uuid,jdbcType=VARCHAR},#{payload,jdbcType=OTHER,typeHandler=com.test.dao.typehandler.JsonTypeHandler})
</insert>

使用时,获取到该Object对象后,可先转成json字符串,再转成对应的对象,如下:

        EventLogPayload eventLogPayload = JsonUtil.parser(JsonUtil.toJson(eventLog.getPayload()), EventLogPayload.class);
05-11 11:09