場景描述

在使用ssm框架寫項目的時候，在構(gòu)建mybatis中發(fā)現(xiàn)報錯；

報錯內(nèi)容（如下）：

Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'singerName' from result set. Cause: java.sql.SQLDataException: Cannot convert string '周杰倫' to java.sql.Time value

項目中的實體類：

public class music{

? ? private Integer MucId;

    private String MucName;

    private String singerName;

    private Time MucTime;

    private String MucPath;

    private String MucImg;

? ? public Integer getMucId() {
        return MucId;
    }

    public void setMucId(Integer mucId) {
        MucId = mucId;
    }

    public String getMucName() {
        return MucName;
    }

    public void setMucName(String mucName) {
        MucName = mucName;
    }

    public String getSingerName() {
        return singerName;
    }

    public void setSingerName(String singerName) {
        this.singerName = singerName;
    }

? ? public Time getMucTime() {
        return MucTime;
    }

    public void setMucTime(Time mucTime) {
        MucTime = mucTime;
    }

    public String getMucPath() {
        return MucPath;
    }

    public void setMucPath(String mucPath) {
        MucPath = mucPath;
    }

    public String getMucImg() {
        return MucImg;
    }

    public void setMucImg(String mucImg) {
        MucImg = mucImg;
    }
? ? 
? ?  public music(String mucName, String singerName, Time mucTime, String mucPath, String mucImg) {
        MucName = mucName;
        this.singerName = singerName;
        MucTime = mucTime;
        MucPath = mucPath;
        MucImg = mucImg;
    }

    @Override
    public String toString() {
        return "music{" +
                "MucId=" + MucId +
                ", MucName='" + MucName + '\'' +
                ", singerName='" + singerName + '\'' +
                ", MucTime=" + MucTime +
                ", MucPath='" + MucPath + '\'' +
                ", MucImg='" + MucImg + '\'' +
                '}';
    }
}

Dao層：

public interface MusicAskDao {

    List<music> findAll();
    

    Integer addMusic(music music);

}

Mapper:

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.yohane.dao.MusicAskDao">

    <resultMap id="musicDo" type="com.yohane.pojo.music">
        <id column="id" property="MucId"/>
        <result column="name" property="MucName"/>
        <result column="musicTime" property="MucTime"/>
        <result column="musicPath" property="MucPath"/>
        <result column="musicImg" property="MucImg"/>
    </resultMap>

    <select id="findAll" resultMap="musicDo">
        select * from music_table
    </select>

    <insert id="addMusic" parameterType="com.yohane.pojo.music">
        insert into music_table(name,singerName,musicTime,musicPath,musicImg) values(#{MucName},#{singerName},#{MucTime},#{MucPath},#{MucImg})
    </insert>



</mapper>

test:

 @Test
    public void testMybatis(){

        SqlSession sqlSession = LoadMybatis.getSqlSession();

        MusicAskDao ask = sqlSession.getMapper(MusicAskDao.class);

        List<music> musicList = ask.findAll();

        for (music value:musicList){
            System.out.println(value.toString());
        }

    }

數(shù)據(jù)庫:

問題：

在查詢所有數(shù)據(jù)的時候出現(xiàn)了

Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'singerName' from result set. Cause: java.sql.SQLDataException: Cannot convert string '周杰倫' to java.sql.Time value

報錯

翻譯過來就是:

原因：org.apache.ibatis.executor.result.ResultMapException:嘗試從結(jié)果集中獲取列“singerName”時出錯。原因：java.sql.SQLDataException:無法轉(zhuǎn)換字符串'周杰倫' 到j(luò)ava.sql.Time值

解決方案：

在使用添加Music到數(shù)據(jù)庫中方法使創(chuàng)建了一個有參構(gòu)造函數(shù)（id不包含，因為在數(shù)據(jù)中是自增）。

添加完之后，查詢的時候就發(fā)現(xiàn)了報錯。

原因是有了有參構(gòu)造函數(shù)之后無參構(gòu)造函數(shù)則不存在，添加上后即可解決。

擴展問題：

mybatis實體為什么要提供一個無參的構(gòu)造函數(shù)

Mybatis 會調(diào)用這個默認構(gòu)造函數(shù)來構(gòu)造實例，即實體類需要通過Mybatis進行動態(tài)反射生成。文章來源地址http://www.zghlxwxcb.cn/news/detail-509613.html