MyBatis映射文件配置之参数传递.md

MyBatis映射文件配置之参数传递

一、单个普通参数

• 直接使用#{参数名}进行取值，mybatis没做特殊处理，参数名可以随便写。

二、单个参数-参数为map，和bean

• UserMapper.java

  //传入一个javabean参数返回list
  List<User>selectAllByConditionBean(User user);
  //传入一个map参数返回list
  List<User>selectAllByConditionMap(Map<String,String> map);
  

• UserMapper.xml

  <select id="selectAllByConditionBean" resultType="com.edu.bean.User">
      select * from user where id=#{id} and user_name=#{userName}
  </select>
  <select id="selectAllByConditionMap" resultType="com.edu.bean.User">
      select * from user  where id=#{id} and user_name=#{userName}
  </select>
  

• TestUserMapper.java

  @Test
  public void testSelectAllByConditionBean(){
      //加载mybatis-config.xml到输入流
      InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
      //通过输入流构建SqlSessionFactory对象
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
      //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
      SqlSession sqlSession = sqlSessionFactory.openSession();
      //通过SqlSession对象得到一个mapper的实现对象
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
  
      User user = mapper.selectById(1);
      List<User> users = mapper.selectAllByConditionBean(user);
  
      System.out.println(users);
  }
  
  @Test
  public void testselectAllByConditionMap(){
      //加载mybatis-config.xml到输入流
      InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
      //通过输入流构建SqlSessionFactory对象
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
      //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
      SqlSession sqlSession = sqlSessionFactory.openSession();
      //通过SqlSession对象得到一个mapper的实现对象
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
  
      User user = mapper.selectById(1);
  
      Map<String,String> map = new HashMap<String, String>();
      map.put("id",user.getId().toString());
      map.put("userName",user.getUserName());
      map.put("gender",user.getGender());
      map.put("email",user.getEmail());
  
      List<User> users = mapper.selectAllByConditionMap(map);
  
      System.out.println(users);
  }
  

三、单个参数-参数为list，数组的形式

• 传入list,默认的键是 list；传入数组,默认的键是array，建议使用 @Param()指定建名

• UserMapper.java

  //查询、参数是list
  List<User> selectByCondition(@Param("list") List<String> list);//默认是list，可通过@Param修改映射
  

• UserMapper.xml

  <select id="selectByCondition" resultType="com.edu.bean.User">
      select * from user where user_name=#{list[0]} and gender=#{list[1]}
  </select>
  

• TestUserMapper.java

  @Test
  public void testSelectByCondition(){
      //加载mybatis-config.xml到输入流
      InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
      //通过输入流构建SqlSessionFactory对象
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
      //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
      SqlSession sqlSession = sqlSessionFactory.openSession();
      //通过SqlSession对象得到一个mapper的实现对象
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
  
      List<String> list = new ArrayList<>();
      list.add("小雷");
      list.add("1");
      List<User> users = mapper.selectByCondition(list);
      System.out.println(users);
  }
  

四、多个参数

• Mybatis会默认构建一个map，键是param1,param2....，或者0,1...值是对应传入的实参,拿参的时候直接写键名就可以，所以可以使用#{param1}，#{param2}取值

• 最优方案：我们可以使用注解(@Param("键名"))指定map的键名：

• UserMapper.java

   //多参数
   List<User> selectNameGender(@Param("name") String n,@Param("gender") String g);
  

• UserMapper.xml

  <select id="selectNameGender" resultType="com.edu.bean.User">
      select * from user where user_name=#{name} and gender=#{gender}
  </select>
  

• TestUserMapper.java

  @Test
  public void testSelectNameGender(){
      //加载mybatis-config.xml到输入流
      InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
      //通过输入流构建SqlSessionFactory对象
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
      //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
      SqlSession sqlSession = sqlSessionFactory.openSession();
      //通过SqlSession对象得到一个mapper的实现对象
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
  
      List<User> list = mapper.selectNameGender("小雷","1");
      System.out.println(list);
  }