17mybatis注解开发

简单理解：

• 使用mybatis注解开发，就不用再写UserMapper.xml配置文件，直接在接口中的方法上面用注解完成。

• 实现简单增删改查，就用Select Delete Update Insert注解。

• 实现复杂查询，就需要用到Results Result One Many注解，组合完成复杂关系的配置。

简单注解：

• @Select("select * from user")
• @Delete("delete from user where id=#{id}")

增删改查注解

注解开发步骤：

1. 实现数据表user(id, username, password)

2. 导入坐标（mysql, mybatis）

3. 在domain包中写User.java类

4. 在dao包中实现UserMapper.java接口，定义方法，并用注解写sql语句

   public interface UserMapper {
   
       @Select("select * from user")
       public List<User> findAll();
   
       @Insert("insert into user values(#{id}, #{username}, #{password})")
       public void save(User user);
   
       @Update("update user set password=#{password} where id=#{id}")
       public void update(User user);
   
       @Delete("delete from user where id=#{id}")
       public void delete(int id);
   }
   

5. 在sqlMapConfig.xml核心配置文件写映射关系

   <?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>
   <!--自定义别名-->
       <typeAliases>
           <typeAlias type="com.domain.User" alias="user"/>
       </typeAliases>
   <!--数据源环境-->
       <environments default="developement">
           <environment id="developement">
               <transactionManager type="JDBC"></transactionManager>
               <dataSource type="POOLED">
                   <property name="driver" value="com.mysql.jdbc.Driver"/>
                   <property name="url" value="jdbc:mysql://localhost:3306/db1"/>
                   <property name="username" value="root"/>
                   <property name="password" value="root"/>
               </dataSource>
           </environment>
       </environments>
   <!--加载映射文件-->
   <!--    <mappers>-->
   <!--        <mapper resource="UserMapper.xml"/>-->
   <!--    </mappers>-->
   <!--加载映射关系-->
       <mappers>
           <package name="com.dao"/>
       </mappers>
   </configuration>
   

6. 测试（和原来一样）

   @Test
   public void test1() throws IOException {
       //  获取核心配置文件
       InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
       // 获取session工厂对象
       SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
       // 获得session会话对象
       SqlSession sqlSession = sqlSessionFactory.openSession();
       // 获得mapper
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       // 执行
       List<User> all = mapper.findAll();
       for (User u : all) {
           System.out.println(u);
       }
       // 释放资源
       sqlSession.close();
   }
   

1v1注解开发

1v1注解开发：

1. 编写User和Order类

2. 编写OrderMapper接口，并定义方法，并用注解开发

   public interface OrderMapper {
       @Select("select *, o.id oid from orders o, user u where o.uid=u.id")
       @Results({
               @Result(column = "oid", property = "id"),
               @Result(column = "ordername", property = "ordername"),
               @Result(column = "total", property = "total"),
               @Result(column = "uid", property = "user.id"),
               @Result(column = "username", property = "user.username"),
               @Result(column = "password", property = "user.password")
       })
       public List<Order> findAll();
   }
   

3. 测试

1v1注解开发的另一种写法：（用这种的较多）

• 首先UserMapper中需要注解开发findById方法

• 再在OrderMapper中开发

  public interface OrderMapper {
      @Select("select * from orders")
      @Results({
              @Result(column = "id", property = "id"),
              @Result(column = "ordername", property = "ordername"),
              @Result(column = "total", property = "total"),
              @Result(
                      property = "user",
                      column = "uid",
                      javaType = User.class,
                      one = @One(select = "com.dao.UserMapper.findById")
              )
      })
      public List<Order> findAll();
  }
  

1vM注解开发

1. 在User中添加成员变量private List<Order> orderList;

2. 在OrderMapper中注解开发findByUid方法

3. 在UserMapper中注解开发

   @Select("select * from user")
   @Results({
           @Result(id=true, column = "id", property = "id"),
           @Result(column = "username", property = "username"),
           @Result(column = "password", property = "password"),
           @Result(
                   property = "orderList",
                   column = "id",
                   javaType = List.class,
                   many = @Many(select = "com.dao.OrderMapper.findByUid")
           )
   })
   public List<User> findAllUserAndOrder();
   

4. 测试

MvM注解开发

多对多关系需要引入一个中间表，所以有三个数据表：一个用户对应多个角色，一个角色对应多个用户

user(id, username, password)
user_role(user_id, role_id)
role(id, rolename)

多对多形式上和一对多差不多：

1. 在User中定义成员变量private List<Role> roleList;

2. 在RoleMapper中注解开发

   @Select("select * from role r, user_role ur where ur.roleId=r.id and ur.userId=uid")
   public List<Role> findByUid(int uid);
   

3. 在UserMapper中注解开发

   @Select("select * from user")
   @Results({
           @Result(id = true, column = "id", property = "id"),
           @Result(column = "username", property = "username"),
           @Result(column = "password", property = "password"),
           @Result(
                   property = "roleList",
                   column = "id",
                   javaType = List.class,
                   many = @Many(select = "com.dao.RoleMapper.findByUid")
           )
   })
   public List<User> findAllUserAndRole();
   

4. 测试