Mybatis的CRUD操作

0. 名词说明

1.namespace

namespace中的包名要和Dao/Mapper接口名一致

2.select

id:命名空间中唯一的标识符，接口中的方法名与映射文件中的SQL语句ID一一对应

resultType:SQL语句返回值类型。【万能的Map】

parameterType:传入SQL语句返回值类型【完整的类名或者别名】

1.Mybatis增删改查的基本实现

0.select 查

0. 编写mybatis-config.xml文件连接数据库

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url"
                          value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=GMT%2B8&amp;useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/dz/dao/UserMapper.xml" />
    </mappers>

</configuration>

 

1.在UserMapper接口中添加对应方法

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();
    //根据id查询用户
    User getUserById(Integer id);
}

 

2.在UserMapper.xml中添加select语句

<mapper namespace="com.dz.dao.UserMapper">
    <!-- 返回值类型为：全限定类名-->
    <select id="getUserList" resultType="com.dz.pojo.User">
        select * from mybatis.user
  </select>
    <select id="getUserById" resultType="com.dz.pojo.User" parameterType="int">
        select * from mybatis.user where id=#{id}
    </select>
</mapper>

 

3.测试类中测试

  @Test
    public void getUserById(){
        //获取SqlSession连接
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.getUserById(1);
        System.out.println(user);
        sqlSession.close();
    }

1.insert 增

步骤与select标签差不多：

1.编写接口

1 Integer addUser(User user);

2. 编写对应UserMapper.xml中的sql语句

 <insert id="addUser" parameterType="com.dz.pojo.User">
      insert into mybatis.user id,name,pwd values (#{id},#{name},#{pwd});
 </insert>

3. 测试

@Test
    public void addUser(){
        SqlSession sqlSession =MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        int res = userMapper.addUser(new User(4,"dz","1213"));
        if(res>0){
            System.out.println("添加成功");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

注：增删改需要提交事务

2.delete 删

1.编写接口

Integer deleteUser(Integer id);

2.编写对应的sql语句

   <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id=#{id}
    </delete>

3. 测试

 public void deleteUser(){
        SqlSession sqlSession =MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();
    }

3.万能的Map(问题)

题：根据密码和用户名查询用户

1.在接口方法中，参数直接传递Map

public interface UserMapper {
    User getUserById2(Map<String,Object> map);
}

 

2.编写sql语句的时候，需要传递参数类型，参数类型为map

<select id="getUserById2" resultType="com.dz.pojo.User" parameterType="map">
        select * from user where name=#{username} and pwd=#{pwd}
    </select>

 

3.使用方法的时候，Map的key为sql中驱动值即可，没有顺序要求

  @Test
    public void selectUserById2(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map<String, Object> map = new HashMap<String,Object>();
        map.put("username","张三");
        map.put("pwd","12345");
        User user = mapper.getUserById2(map);
        sqlSession.close();
    }