一、定义接口
public interface OraBackupInfoMapper { List<String> queryRacList(); }
二、开发*mapper.xml
<?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="com.hidata.devops.selfops.mapper.OraBackupInfoMapper"> <select id="queryRacList" resultType="java.util.List"> SELECT DISTINCT rac_name FROM `ora_backup_info` </select> </mapper>
三、执行测试类
@Test public void testApi(){ List<String> racList = oraBackupInfoMapper.queryRacList(); System.out.println(racList); }
运行结果报错：
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: ### Error querying database. Cause: java.lang.UnsupportedOperationException ### The error may exist in file [D:\workspace_ruoyi_code\branch\hipaas\paas\target\classes\mapper\oracle\OraBackupInfoMapper.xml] ### The error may involve com.hidata.devops.selfops.mapper.OraBackupInfoMapper.queryRacList ### The error occurred while handling results ### SQL: SELECT DISTINCT rac_name FROM `ora_backup_info` ### Cause: java.lang.UnsupportedOperationException
四、解决办法
将resultType=“java.util.List” 修改为 resultType=“String”
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.hidata.devops.selfops.mapper.OraBackupInfoMapper"> <select id="queryRacList" resultType="String"> SELECT DISTINCT rac_name FROM `ora_backup_info` </select> </mapper>
