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MyBatis 如何使用set标签呢？

set标签的功能简介

set标签主要用于结合update语句动态更新列信息，
使用set标签可避免条件末尾多余的逗号

例 使用 id 修改名称或备注
UserInfoMapper.xml

SELECT id,name,notes FROM UserInfoid=#{id}UPDATE UserInfoname=#{name}notes=#{notes}WHERE id=#{id}

UserInfoMapper 类

package com.java265.mapper;
import java.util.List;
import org.apache.ibatis.annotations.Param;
import com.java265.po.UserInfo;
public interface UserInfoMapper {public List selectUserInfo(UserInfo site);public int updateUserInfo(UserInfo site);
}

测试类

package com.java265.test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import com.java265.mapper.UserInfoMapper;
import com.java265.po.UserInfo;
public class Test {public static void main(String[] args) throws IOException {InputStream config = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(config);SqlSession ss = ssf.openSession();UserInfo userInfo = new UserInfo();userInfo.setId(1);userInfo.setNotes("java爱好者");// 执行update语句前List userList = ss.getMapper(UserInfoMapper.class).selectUserInfo(userInfo);for (UserInfo t : userList) {System.out.println(t);}int num = ss.getMapper(UserInfoMapper.class).updateUserInfo(userInfo);System.out.println("影响数据库行数" + num);// 执行update语句后List userList2 = ss.getMapper(UserInfoMapper.class).selectUserInfo(userInfo);for (UserInfo t : userList2) {System.out.println(t);}ss.commit();ss.close();}
}

输出结果
DEBUG [main] - ==> Preparing: SELECT * FROM UserInfo WHERE id=?
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <== Total: 1
UserInfo[id=1,name=王二,notes=java爱好者]
DEBUG [main] - ==> Preparing: UPDATE UserInfo SET notes=? where id=?
DEBUG [main] - ==> Parameters: java爱好者(String), 1(Integer)
DEBUG [main] - <== Updates: 1
影响数据库行数1
DEBUG [main] - ==> Preparing: SELECT * FROM UserInfo WHERE id=?
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <== Total: 1
UserInfo[id=1,name=王二,notes=java爱好者]