Preparations: Create com.jiang.pojo
create entity classes
package com.jiang.pojo;
import lombok.Data;
//实体类
@Data
public class User {
private int id;
private String name;
private String pwd;
}
1、namespace
Package name to the namespace and Dao / package name mapper interface consistent!
2、select
Select, query;
- id: is corresponding to the method name in the namespace;
- resultType: Sql statement is executed Return Value!
- parameterType: parameter type!
Write
UserMapper
Interface//根据ID查询用户 User getUserById(int id);
Write the corresponding
UserMapper
sql statement<select id="getUserById" parameterType="int" resultType="com.jiang.pojo.User"> select * from mybatis.user where id = #{id} </select>
test
@Test public void getUserById() { SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); User user = mapper.getUserById(1); System.out.println(user); sqlSession.close(); }
3、Insert
Write
UserMapper
Interface//insert一个用户 int addUser(User user);
Write the corresponding
UserMapper
sql statement<insert id="addUser" parameterType="com.jiang.pojo.User"> insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd}); </insert>
test
package com.jiang.dao; import com.jiang.pojo.User; import com.jiang.utils.MybatisUtils; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import java.util.List; public class UserDaoTest { @Test public void getUserLike(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); int i = mapper.addUser(new User(5, "姜嘉航","465123")); if (i>0){ System.out.println("插入成功"); } //提交事务 sqlSession.commit(); sqlSession.close(); } }
4、update
Write
UserMapper
Interface//修改用户 int updateUser(User user);
Write the corresponding
UserMapper
sql statement<update id="updateUser" parameterType="com.jiang.pojo.User"> update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id} ; </update>
test
package com.jiang.dao; import com.jiang.pojo.User; import com.jiang.utils.MybatisUtils; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import java.util.List; public class UserDaoTest { @Test public void getUserLike(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); int i = mapper.updateUser(new User(5, "哈哈","1265123")); if (i>0){ System.out.println("更新成功"); } //提交事务 sqlSession.commit(); sqlSession.close(); } }
5、Delete
Write
UserMapper
Interface//删除一个用户 int deleteUser(int id);
Write the corresponding
UserMapper
sql statement<delete id="deleteUser" parameterType="int"> delete from mybatis.user where id = #{id}; </delete>
test
package com.jiang.dao; import com.jiang.pojo.User; import com.jiang.utils.MybatisUtils; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import java.util.List; public class UserDaoTest { @Test public void getUserLike(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); mapper.deleteUser(5); System.out.println("删除成功"); sqlSession.commit(); sqlSession.close(); } }
important point:
- CRUD need to commit the transaction! (SqlSession.commit ();)