Mybatis的SQL语句返回结果有两种

resultType

查询出的字段在相应的POJO中必须有和它相同的字段对应，或者基本数据类型

适合简单查询

resultMap

需要自定义字段，或者多表查询，一对多等关系，比resultType更强大

适合复杂查询

项目结构

pom.xml

4.0.0

net.cyb

cyb-mybatis

1.0-SNAPSHOT

org.mybatis

mybatis

3.5.4

mysql

mysql-connector-java

8.0.20

org.slf4j

slf4j-log4j12

1.7.30

mybatis-config.xml

/p>

PUBLIC "-//mybatis.org//DTD Config 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-config.dtd">

db.properties

db.driver=com.mysql.cj.jdbc.Driver

db.url=jdbc:mysql://127.0.0.1:3306/cybclass

db.username=root

db.password=root

log4j.properties

#dev env [debug] product env [info]

log4j.rootLogger=ERROR, stdout

# Console output...

# 细化到打印某个mapper

# log4j.logger.包名.方法名=TRACE

log4j.logger.net.cybclass.online=TRACE

#log4j.logger.net.cybclass.online.dao.VideoMapper.selectById=TRACE

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

VideoMapper.xml

/p>

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

id,title title2,summary

selectfrom video where id=#{id}

VideoMapper.java

packagenet.cybclass.online.dao;importnet.cybclass.online.domain.Video;importorg.apache.ibatis.annotations.Param;importorg.apache.ibatis.annotations.Select;importjava.util.List;importjava.util.Map;public interfaceVideoMapper {

Video selectBaseFieldByIdWithResultMap(intid);

}

Video.java

packagenet.cybclass.online.domain;importjava.util.Date;/*** 视频类*/

public classVideo {//内码

private intid;//视频标题

privateString title;//视频详情

privateString summary;//视频封面

privateString coverImg;//加个

private intprice;private intc_id;//评分

private doublepoint;//创建日期

privateDate create_time;public intgetId() {returnid;

}public void setId(intid) {this.id =id;

}publicString getTitle() {returntitle;

}public voidsetTitle(String title) {this.title =title;

}publicString getSummary() {returnsummary;

}public voidsetSummary(String summary) {this.summary =summary;

}publicString getCoverImg() {returncoverImg;

}public voidsetCoverImg(String coverImg) {this.coverImg =coverImg;

}public intgetPrice() {returnprice;

}public void setPrice(intprice) {this.price =price;

}public intgetC_id() {returnc_id;

}public void setC_id(intc_id) {this.c_id =c_id;

}public doublegetPoint() {returnpoint;

}public void setPoint(doublepoint) {this.point =point;

}publicDate getCreate_time() {returncreate_time;

}public voidsetCreate_time(Date create_time) {this.create_time =create_time;

}

@OverridepublicString toString() {return "Video{" +

"id=" + id +

", title=‘" + title + ‘\‘‘ +

", summary=‘" + summary + ‘\‘‘ +

", coverImg=‘" + coverImg + ‘\‘‘ +

", price=" + price +

", c_id=" + c_id +

", point=" + point +

", create_time=" + create_time +

‘}‘;

}

}

SqlSessionDemo.java

packagenet.cybclass.online;importnet.cybclass.online.dao.VideoMapper;importnet.cybclass.online.domain.Video;importorg.apache.ibatis.io.Resources;importorg.apache.ibatis.session.SqlSession;importorg.apache.ibatis.session.SqlSessionFactory;importorg.apache.ibatis.session.SqlSessionFactoryBuilder;importjava.io.IOException;importjava.io.InputStream;import java.util.*;public classSqlSessionDemo {public static void main(String[] args) throwsIOException {

String resouce="config/mybatis-config.xml";

InputStream resourceAsStream=Resources.getResourceAsStream(resouce);

SqlSessionFactory build= newSqlSessionFactoryBuilder().build(resourceAsStream);try(SqlSession session=build.openSession()){

VideoMapper mapper= session.getMapper(VideoMapper.class);

Video video= mapper.selectBaseFieldByIdWithResultMap(52);

System.out.println(video.toString());

}catch(Exception e){

e.printStackTrace();

}

}

}