MyBatis——增删改查(CRUD)
准备工作:创建在com.jiang.pojo
中创建实体类
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
namespace中的包名要和 Dao/mapper 接口的包名一致!
2、select
选择,查询语句;
- id : 就是对应的namespace中的方法名;
- resultType:Sql语句执行的返回值!
- parameterType : 参数类型!
-
编写
UserMapper
接口//根据ID查询用户 User getUserById(int id);
-
编写对应的
UserMapper
中的sql语句<select id="getUserById" parameterType="int" resultType="com.jiang.pojo.User"> select * from mybatis.user where id = #{id} </select>
-
测试
@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
-
编写
UserMapper
接口//insert一个用户 int addUser(User user);
-
编写对应的
UserMapper
中的sql语句<insert id="addUser" parameterType="com.jiang.pojo.User"> insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd}); </insert>
-
测试
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
-
编写
UserMapper
接口//修改用户 int updateUser(User user);
-
编写对应的
UserMapper
中的sql语句<update id="updateUser" parameterType="com.jiang.pojo.User"> update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id} ; </update>
-
测试
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
-
编写
UserMapper
接口//删除一个用户 int deleteUser(int id);
-
编写对应的
UserMapper
中的sql语句<delete id="deleteUser" parameterType="int"> delete from mybatis.user where id = #{id}; </delete>
-
测试
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(); } }
注意点:
- 增删改需要提交事务!( sqlSession.commit();)
6、万能Map
假设,我们的实体类,或者数据库中的表,字段或者参数过多,我们应当考虑使用Map!
- 编写接口
//万能的Map
int addUser2(Map<String,Object> map);
- 编写mapper.xml
<!--对象中的属性,可以直接取出来 传递map的key-->
<insert id="addUser" parameterType="map">
insert into mybatis.user (id, pwd) values (#{userid},#{passWord});
</insert>
- 测试
@Test
public void addUser2(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
Map<String, Object> map = new HashMap<String, Object>();
map.put("userid",5);
map.put("passWord","2222333");
mapper.addUser2(map);
sqlSession.close();
}
Map传递参数,直接在sql中取出key即可! 【parameterType="map"】
对象传递参数,直接在sql中取对象的属性即可!【parameterType="Object"】
只有一个基本类型参数的情况下,可以直接在sql中取到!
多个参数用Map,或者注解!
7、模糊查询
-
Java代码执行的时候,传递通配符 % %
- 编写接口
List<User> userList = mapper.getUserLike("%李%");
2.编写mapper.xml
<select id="getUserLike" resultType="com.kuang.pojo.User"> select * from mybatis.user where name like "%"#{value}"%" </select>
3.测试
public class UserDaoTest { @Test public void getUserLike(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); List<User> userList = mapper.getUserLike("%李%"); for (User user : userList) { System.out.println(user); } sqlSession.close(); }
-
在sql拼接中使用通配符!
select * from mybatis.user where name like "%"#{value}"%"