MyBatis学习笔记——03CRUD

一. namespace

• namespace中的包名要和 Dao/mapper 接口的包名一致！

  <mapper namespace="com.hjf.dao.PeopleMapper">
  	...
  mapper>
  

二. select语句

1. 说明

1. select: 查询语句
2. id: 对应方法名
3. resultType: sql语句执行的返回值类型(完整的名称)
4. parameterType: 参数类型

2. 代码

1. 编写接口

   /**
    * 获取人员信息列表
    * @return
    */
   List<People> getPeopleList();
   
   /**
    * 通过id查询人员信息
    * @param id
    * @return
    */
   People getPeopleById(int id);
   
   /**
    * 通过用户名模糊查找
    * @param name
    * @return
    */
   List<People> getPeopleListByLike(String name);
   

2. 编写对应的mapper中的sql语句

   
   <select id="getPeopleList" resultType="com.hjf.pojo.People">
       select * from people
   select>
   
   
   <select id="getPeopleById" resultType="com.hjf.pojo.People" parameterType="int">
       select * from people where id=#{id}
   select>
   
   <select id="getPeopleListByLike" resultType="com.hjf.pojo.People" parameterType="String">
       select id, name, pwd from people where name like #{name}
   select>
   
   

3. 编写测试函数

   @Test
       public void testGetPeopleList() {
           // 1. 获得sqlSession的对象
           SqlSession sqlSession = MybatisUtils.getSqlSession();
           // 方式1: getMapper
           PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
           List<People> peopleList = mapper.getPeopleList();
   
           // 方法2:
           // List peopleList = sqlSession.selectList("com.hjf.dao.PeopleMapper.getPeopleList");
   
           for (People people : peopleList) {
               System.out.println(people);
           }
   
           // 关闭资源
           sqlSession.close();
       }
   
       @Test
       public void testGetPeopleById(){
           SqlSession sqlSession = MybatisUtils.getSqlSession();
           PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
           People people = mapper.getPeopleById(3);
           System.out.println(people);
           sqlSession.close();
       }
       
   	@Test
       public void testGetPeopleListByLike(){
           SqlSession sqlSession = MybatisUtils.getSqlSession();
           PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
           List<People> peopleList = mapper.getPeopleListByLike("%张%");
           for (People people: peopleList) {
               System.out.println(people);
           }
   
           sqlSession.close();
       }
   
   

三. Insert

1. 代码

1. 编写接口

   /**
    * 添加人员信息
    * @param people
    * @return
    */
   int addPeople(People people);
   

2. 编写对应的mapper中的sql语句

   
   <insert id="addPeople" parameterType="com.hjf.pojo.People">
       insert into people(id, name, pwd) values(#{id}, #{name}, #{pwd})
   insert>
   

3. 编写测试函数

   @Test
   public void testAddPeople() {
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
       int flag = mapper.addPeople(new People(8, "people8", "111111"));
       if (flag > 0) {
           System.out.println("添加人员信息成功!");
       } else {
           System.out.println("添加人员信息失败!");
       }
       // 提交事务
       // 增,删,改必须提交事务
       sqlSession.commit();
       sqlSession.close();
   }
   
   

四. update

1. 代码

1. 编写接口

    /**
     * 修改人员信息
     * @param people
     * @return
     */
    int updatePeople(People people);
   

2. 编写对应的mapper中的sql语句

   <update id="updatePeople" parameterType="com.hjf.pojo.People">
       update people set name=#{name}, pwd=#{pwd} where id=#{id}
   update>
   

3. 编写测试函数

   @Test
   public void testUpdatePeople() {
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
       int flag = mapper.updatePeople(new People(8, "用户8", "888888"));
       if (flag > 0) {
           System.out.println("修改用户成功!");
       } else {
           System.out.println("修改用户失败");
       }
       sqlSession.commit();
       sqlSession.close();
   }
   

五. Delete

1. 代码

1. 编写接口

   /**
    * 通过id删除人员信息
    * @param id
    * @return
    */
   int delPeopleById(int id);
   

2. 编写对应的mapper中的sql语句

   <delete id="delPeopleById" parameterType="int">
       delete from people where id=#{id}
   delete>
   

3. 编写测试函数

   @Test
   public void testDelPeopleById(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
       int flag = mapper.delPeopleById(8);
       if (flag > 0) {
           System.out.println("删除用户成功!");
       } else {
           System.out.println("删除用户失败");
       }
       sqlSession.commit();
       sqlSession.close();
   }
   

六. 万能Map

1. 说明

1. 之前的方法添加或修改时需要传入实体类中的所有参数, 如果实体类中的属性过多时, 就会很麻烦
2. 此时, 我们可以考虑使用Map来传指定的参数

2. 代码

1. 编写接口

    /**
     * 通过map传递参数
     * @param map
     * @return
     */
    int addPeople2(Map<String, Object> map);
   

2. 编写对应的mapper中的sql语句

   
   <insert id="addPeople2" parameterType="map">
       insert into people(id, name) values(#{uid}, #{username})
   insert>
   

3. 编写测试函数

   @Test
   public void testAddPeople2() {
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       PeopleMapper mapper = sqlSession.getMapper(PeopleMapper.class);
       HashMap<String, Object> map = new HashMap<String, Object>();
       map.put("uid", "15");
       map.put("username", "赵子龙");
   
       int flag = mapper.addPeople2(map);
       if (flag > 0) {
           System.out.println("添加人员信息成功!");
       } else {
           System.out.println("添加人员信息失败!");
       }
       // 提交事务
       // 增,删,改必须提交事务
       sqlSession.commit();
       sqlSession.close();
   }
   

说明:

1. 本文参考了狂神的Mybatis的课件
2. 课程链接