4.Mybatis增删改查的简单实现
4.Mybatis增删改查的简单实现
DencyCheng
发布于 2020-11-17 02:45:03
发布于 2020-11-17 02:45:03
代码可运行
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代码可运行
1.namespace
namespace中的包名要和 mapper 接口名一致！
2.select
选择，查询语句；
- id : 就是对应的namespace中的方法名
- resultType : sql语句执行返回值的类型
- parameterType : 参数类型
1.编写接口
/**
* 调用xml方式
* @param id
* @return
*/
public User selectUserForXml(Integer id);2.编写对应mapper中的sql语句
<select id="selectUserForXml" resultType="com.dencycheng.entiy.User" parameterType="int">
select * from user where id = #{id}
</select>3.测试
@Test
public void selectOne() {
SqlSession sqlSession = null;
try {
//获取SqlSession
sqlSession = MybatisUtils.getSqlSession();
//获取mapper
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//xml第二种方式
User user = mapper.selectUserForXml(2);
System.out.println(user);
} finally {
//关闭sqlSession
sqlSession.close();
}
}User{id=2, name='黑猫', pwd='212122'}3.insert
1.编写接口
/**
* 增加
* @param user
*/
public void save(User user);2.编写对应mapper中的sql语句
<insert id="save" parameterType="com.dencycheng.entiy.User">
insert user (name,pwd) values (#{name},#{pwd})
</insert>3.测试
//增删改需要提交事物
@Test
public void save(){
SqlSession sqlSession = null;
try {
//获取SqlSession
sqlSession = MybatisUtils.getSqlSession();
//获取mapper
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
int save = mapper.save(new User("21212121", "1"));
System.out.println("执行行数："+save);
sqlSession.commit();
} finally {
//关闭sqlSession
sqlSession.close();
}
}执行行数：14.update
1.编写接口
/**
* 更新
* @param user
*/
public void update(User user);2.编写对应mapper中的sql语句
<update id="update" parameterType="com.dencycheng.entiy.User">
update user set name = #{name}, pwd = #{pwd} where id = #{id}
</update>3.测试
@Test
public void update(){
SqlSession sqlSession = null;
try {
//获取SqlSession
sqlSession = MybatisUtils.getSqlSession();
//获取mapper
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
mapper.update(new User(1,"z","1"));
sqlSession.commit();
} finally {
//关闭sqlSession
sqlSession.close();
}
}5.delete
1.编写接口
/**
* 删除
* @param id
*/
public void delete(Integer id);2.编写对应mapper中的sql语句
<delete id="delete" parameterType="int">
delete from user where id = #{id}
</delete>3.测试
@Test
public void delete(){
SqlSession sqlSession = null;
try {
//获取SqlSession
sqlSession = MybatisUtils.getSqlSession();
//获取mapper
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
mapper.delete(1);
sqlSession.commit();
} finally {
//关闭sqlSession
sqlSession.close();
}
}注意：mybatis在增删改的时候不会默认提交事物。有两种方式提交
1.在执行完语句后加上
sqlSession.commit();2.在打开session的时候设置自动提交
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}SqlSessionFactory SqlSession openSession(boolean var1);DefaultSqlSessionFactory
public SqlSession openSession(boolean autoCommit) {
return this.openSessionFromDataSource(this.configuration.getDefaultExecutorType(), (TransactionIsolationLevel)null, autoCommit);
} public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession(true);
}常见错误
- 标签不要匹配错。
- resource 绑定mapper，需要使用路径
<mappers>
<mapper resource="mybatis/UserMapper.xml"/>
</mappers>本文参与 腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。
原始发表：2020/11/15 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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