JAVA日記之mybatis-3一對一,一對多,多對多xml與註解配置

時間  2020-11-01
標籤 java sql app dom 學習 測試 spa 3d code 欄目 Java 简体版
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1.Mybatis多表查詢
1.1 一對一查詢
1.1.1 一對一查詢的模型
用戶表和訂單表的關係爲，一個用戶有多個訂單，一個訂單隻從屬於一個用戶


java

一對一查詢的需求：查詢一個訂單，與此同時查詢出該訂單所屬的用戶sql

 

1.1.2一對一查詢的語句
對應的sql語句：select * from orders o,user u where o.uid=u.id;
app

查詢的結果以下：dom

 

1.1.3 建立Order和User實體學習

public class Order {測試

private int id;
private Date ordertime;
private double total;

ui

//表明當前訂單從屬於哪個客戶
private User user;
}

spa

public class User {

private int id;
private String username;
private String password;
private Date birthday;




3d

}code

1.1.4 建立OrderMapper接口
public interface OrderMapper { List<Order> findAll(); }


1.1.5 配置OrderMapper.xml

<mapper namespace="com.itheima.mapper.OrderMapper">
<resultMap id="orderMap" type="com.itheima.domain.Order">
<result column="uid" property="user.id"></result>
<result column="username" property="user.username"></result>
<result column="password" property="user.password"></result>
<result column="birthday" property="user.birthday"></result>
</resultMap>
<select id="findAll" resultMap="orderMap">
select * from orders o,user u where o.uid=u.id
</select>
</mapper>









其中還能夠配置以下：

<resultMap id="orderMap" type="com.itheima.domain.Order">
<result property="id" column="id"></result>
<result property="ordertime" column="ordertime"></result>
<result property="total" column="total"></result>
<association property="user" javaType="com.itheima.domain.User">
<result column="uid" property="id"></result>
<result column="username" property="username"></result>
<result column="password" property="password"></result>
<result column="birthday" property="birthday"></result>
</association>
</resultMap>









1.1.6 測試結果

OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);
List<Order> all = mapper.findAll();
for(Order order : all){
System.out.println(order);
}





 

 

 

1.2 一對多查詢

1.2.1 一對多查詢的模型

用戶表和訂單表的關係爲，一個用戶有多個訂單，一個訂單隻從屬於一個用戶

一對多查詢的需求：查詢一個用戶，與此同時查詢出該用戶具備的訂單

 
 
 
 
 
 
 
 
 
 
 
 
  
 
1.2.2 一對多查詢的語句
 
 
對應的sql語句：select *,o.id oid from user u left join orders o on u.id=o.uid;
 
 
查詢的結果以下：
 
 
 
 
 
 
 
 
 
 
 
 
  
 
1.2.3 修改User實體
 
 
public class Order {
 
 
 private int id;
 private Date ordertime;
 private double total;

 
 
 //表明當前訂單從屬於哪個客戶
 private User user;
}

 
 
public class User {
 
 private int id;
 private String username;
 private String password;
 private Date birthday;
 //表明當前用戶具有哪些訂單
 private List<Order> orderList;
}







 
  
 
1.2.4 建立UserMapper接口
 
 
public interface UserMapper { List<User> findAll(); } 
 
 
 
 
  
 
1.2.5 配置UserMapper.xml
 
 
<mapper namespace="com.itheima.mapper.UserMapper">
 <resultMap id="userMap" type="com.itheima.domain.User">
 <result column="id" property="id"></result>
 <result column="username" property="username"></result>
 <result column="password" property="password"></result>
 <result column="birthday" property="birthday"></result>
 <collection property="orderList" ofType="com.itheima.domain.Order">
 <result column="oid" property="id"></result>
 <result column="ordertime" property="ordertime"></result>
 <result column="total" property="total"></result>
 </collection>
 </resultMap>
 <select id="findAll" resultMap="userMap">
 select *,o.id oid from user u left join orders o on u.id=o.uid
 </select>
</mapper>














 
  
 
1.2.6 測試結果
 
 
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAll();
for(User user : all){
 System.out.println(user.getUsername());
 List<Order> orderList = user.getOrderList();
 for(Order order : orderList){
 System.out.println(order);
 }
 System.out.println("----------------------------------");
}











 
 
 
 
 
 
 
 
 
 
 
 
  
 
1.3 多對多查詢
 
  
 
1.3.1 多對多查詢的模型
 
 
用戶表和角色表的關係爲，一個用戶有多個角色，一個角色被多個用戶使用
 
 
多對多查詢的需求：查詢用戶同時查詢出該用戶的全部角色
 
 
 
 
 
 
 
1.3.2 多對多查詢的語句
 
 
對應的sql語句：select u.,r.,r.id rid from user u left join user_role ur on u.id=ur.user_id
 
 
inner join role r on ur.role_id=r.id;
 
 
查詢的結果以下：
 
 


 
 
 
 
 
1.3.3 建立Role實體，修改User實體
 
 
public class User {
 private int id;
 private String username;
 private String password;
 private Date birthday;
 //表明當前用戶具有哪些訂單
 private List<Order> orderList;
 //表明當前用戶具有哪些角色
 private List<Role> roleList;
}








 
 
public class Role {
 
 
 private int id;
 private String rolename;
 
 
}
 
  
 
1.3.4 添加UserMapper接口方法
 
 
List<User> findAllUserAndRole(); 
 
  
 
1.3.5 配置UserMapper.xml
 
 
 
 
 
<resultMap id="userRoleMap" type="com.itheima.domain.User">
 <result column="id" property="id"></result>
 <result column="username" property="username"></result>
 <result column="password" property="password"></result>
 <result column="birthday" property="birthday"></result>
 <collection property="roleList" ofType="com.itheima.domain.Role">
 <result column="rid" property="id"></result>
 <result column="rolename" property="rolename"></result>
 </collection>
</resultMap>
<select id="findAllUserAndRole" resultMap="userRoleMap">
 select u.*,r.*,r.id rid from user u left join user_role ur on u.id=ur.user_id
 inner join role r on ur.role_id=r.id
</select>












 
  
 
1.3.6 測試結果
 
 
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAllUserAndRole();
for(User user : all){
 System.out.println(user.getUsername());
 List<Role> roleList = user.getRoleList();
 for(Role role : roleList){
 System.out.println(role);
 }
 System.out.println("----------------------------------");
}










 
 
 
 
 
 
 
 
 
 
 
.4 知識小結
MyBatis多表配置方式：
 
 
一對一配置：使用作配置
 
 
一對多配置：使用+作配置
 
 
多對多配置：使用+作配置
 
 
2.Mybatis的註解開發
2.1 MyBatis的經常使用註解
這幾年來註解開發愈來愈流行，Mybatis也可使用註解開發方式，這樣咱們就能夠減小編寫Mapper

 
 
映射文件了。咱們先圍繞一些基本的CRUD來學習，再學習複雜映射多表操做。
 
 
@Insert：實現新增
 
 
@Update：實現更新
 
 
@Delete：實現刪除
 
 
@Select：實現查詢
 
 
@Result：實現結果集封裝
 
 
@Results：能夠與@Result 一塊兒使用，封裝多個結果集
 
 
@One：實現一對一結果集封裝
 
 
@Many：實現一對多結果集封裝
 
 
2.2 MyBatis的增刪改查
咱們完成簡單的user表的增刪改查的操做
 
 
private UserMapper userMapper;
 
 
@Before
public void before() throws IOException {
 InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
 SqlSessionFactory sqlSessionFactory = new 
 SqlSessionFactoryBuilder().build(resourceAsStream);
 SqlSession sqlSession = sqlSessionFactory.openSession(true);
 userMapper = sqlSession.getMapper(UserMapper.class);
}






 
 
@Test
public void testAdd() {
 User user = new User();
 user.setUsername("測試數據");
 user.setPassword("123");
 user.setBirthday(new Date());
 userMapper.add(user);
}
@Test
public void testUpdate() throws IOException {
 User user = new User();
 user.setId(16);
 user.setUsername("測試數據修改");
 user.setPassword("abc");
 user.setBirthday(new Date());
 userMapper.update(user);
}















 
 
@Test
public void testDelete() throws IOException {
 userMapper.delete(16);
}
@Test
public void testFindById() throws IOException {
 User user = userMapper.findById(1);
 System.out.println(user);
}
@Test
public void testFindAll() throws IOException {
 List<User> all = userMapper.findAll();
 for(User user : all){
 System.out.println(user);
 }
}














 
 
修改MyBatis的核心配置文件，咱們使用了註解替代的映射文件，因此咱們只須要加載使用了註解的Mapper接口便可
 
 
 
 
 <mappers> <!--掃描使用註解的類--> <mapper class="com.itheima.mapper.UserMapper"></mapper> </mappers>
 
 
或者指定掃描包含映射關係的接口所在的包也能夠
 
 
<mappers> <!--掃描使用註解的類所在的包--> <package name="com.itheima.mapper"></package> </mappers>
 
  
 
2.3 MyBatis的註解實現複雜映射開發
 
 
實現複雜關係映射以前咱們能夠在映射文件中經過配置來實現，使用註解開發後，咱們可使用@Results註解，@Result註解，@One註解，@Many註解組合完成複雜關係的配置
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
2.4 一對一查詢
 
  
 
2.4.1 一對一查詢的模型
 
 
用戶表和訂單表的關係爲，一個用戶有多個訂單，一個訂單隻從屬於一個用戶
 
 
一對一查詢的需求：查詢一個訂單，與此同時查詢出該訂單所屬的用戶
 
 
[外鏈圖片轉存失敗(img-wmckNwf4-1562073026161)(img\圖片12.png)]
 
 
 
 
  
 
2.4.2 一對一查詢的語句
 
 
對應的sql語句：
 
 
select * from orders; select * from user where id=查詢出訂單的uid;
 
 
查詢的結果以下：
 
 
 
 
 
 
 
  
 
2.4.3 建立Order和User實體
 
 
 
 
 
public class Order {
 
 
 private int id;
 private Date ordertime;
 private double total;

 
 
 //表明當前訂單從屬於哪個客戶
 private User user;
}

 
 
public class User {
 
 private int id;
 private String username;
 private String password;
 private Date birthday;




 
 
}
 
  
 
2.4.4 建立OrderMapper接口
 
 
public interface OrderMapper { List<Order> findAll(); }


 
  
 
2.4.5 使用註解配置Mapper
 
 
public interface OrderMapper {
 @Select("select * from orders")
 @Results({
 @Result(id=true,property = "id",column = "id"),
 @Result(property = "ordertime",column = "ordertime"),
 @Result(property = "total",column = "total"),
 @Result(property = "user",column = "uid",
 javaType = User.class,
 one = @One(select = "com.itheima.mapper.UserMapper.findById"))
 })
 List<Order> findAll();
}public interface UserMapper { @Select("select * from user where id=#{id}") User findById(int id); } 










 
  
 
2.4.6 測試結果
 
 
@Test
public void testSelectOrderAndUser() {
 List<Order> all = orderMapper.findAll();
 for(Order order : all){
 System.out.println(order);
 }
}





 
 
 
 
 
 
 
 
 
 
  
 
2.5 一對多查詢
 
  
 
2.5.1 一對多查詢的模型
 
 
用戶表和訂單表的關係爲，一個用戶有多個訂單，一個訂單隻從屬於一個用戶
 
 
一對多查詢的需求：查詢一個用戶，與此同時查詢出該用戶具備的訂單
 
 
[外鏈圖片轉存失敗(img-aaaElVnT-1562073026164)(img\圖片15.png)]
 
  
 
2.5.2 一對多查詢的語句
 
 
對應的sql語句：
 
 
select * from user;

select * from orders where uid=查詢出用戶的id;
 
 
 
 
 
 
 
 
查詢的結果以下：
 
 
[外鏈圖片轉存失敗(img-8eGJNkVv-1562073026165)(img\圖片16.png)]
 
 
 
 
 
2.5.3 修改User實體
 
 
public class Order {
 
 
 private int id;
 private Date ordertime;
 private double total;

 
 
 //表明當前訂單從屬於哪個客戶
 private User user;
}

 
 
public class User {
 
 private int id;
 private String username;
 private String password;
 private Date birthday;
 //表明當前用戶具有哪些訂單
 private List<Order> orderList;
}







 
  
 
2.5.4 建立UserMapper接口
 
 
List<User> findAllUserAndOrder(); 
 
  
 
2.5.5 使用註解配置Mapper
 
 
public interface UserMapper {
 @Select("select * from user")
 @Results({
 @Result(id = true,property = "id",column = "id"),
 @Result(property = "username",column = "username"),
 @Result(property = "password",column = "password"),
 @Result(property = "birthday",column = "birthday"),
 @Result(property = "orderList",column = "id",
 javaType = List.class,
 many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid"))
 })
 List<User> findAllUserAndOrder();
}











 
 
public interface OrderMapper {
 @Select("select * from orders where uid=#{uid}")
 List<Order> findByUid(int uid);

 
 
}
 
  
 
2.5.6 測試結果
 
 
List<User> all = userMapper.findAllUserAndOrder();
for(User user : all){
 System.out.println(user.getUsername());
 List<Order> orderList = user.getOrderList();
 for(Order order : orderList){
 System.out.println(order);
 }
 System.out.println("-----------------------------");
}









 
 
 
 
 
 
 
  
 
2.6 多對多查詢
 
  
 
2.6.1 多對多查詢的模型
 
 
用戶表和角色表的關係爲，一個用戶有多個角色，一個角色被多個用戶使用
 
 
多對多查詢的需求：查詢用戶同時查詢出該用戶的全部角色
 
 
[外鏈圖片轉存失敗(img-JM72Dl4Q-1562073026166)(img\圖片18.png)]
 
  
 
2.6.2 多對多查詢的語句
 
 
對應的sql語句：
 
 
 
 
select * from user; select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=用戶的id
 
 
查詢的結果以下：
 
 
 
 
 
 
 
 
 
 
 
 
  
 
2.6.3 建立Role實體，修改User實體
 
 
 
 
public class User {
 private int id;
 private String username;
 private String password;
 private Date birthday;
 //表明當前用戶具有哪些訂單
 private List<Order> orderList;
 //表明當前用戶具有哪些角色
 private List<Role> roleList;
}








 
 
 
 
public class Role {
 
 
 
 
 private int id;
 private String rolename;
 
 
 
 
}
 
 
public class User {
 private int id;
 private String username;
 private String password;
 private Date birthday;
 //表明當前用戶具有哪些訂單
 private List<Order> orderList;
 //表明當前用戶具有哪些角色
 private List<Role> roleList;
}








 
 
public class Role {
 
 
 private int id;
 private String rolename;
 
 
}
 
  
 
2.6.5 使用註解配置Mapper
 
 
public interface UserMapper {
 @Select("select * from user")
 @Results({
 @Result(id = true,property = "id",column = "id"),
 @Result(property = "username",column = "username"),
 @Result(property = "password",column = "password"),
 @Result(property = "birthday",column = "birthday"),
 @Result(property = "roleList",column = "id",
 javaType = List.class,
 many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid"))
})
List<User> findAllUserAndRole();}










 
 
 
 
 
public interface RoleMapper {
 @Select("select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=#{uid}")
 List<Role> findByUid(int uid);
}


 
  
 
2.6.6 測試結果
 
 
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
 
 
List<User> all = mapper.findAllUserAndRole();
for(User user : all){
 System.out.println(user.getUsername());
 List<Role> roleList = user.getRoleList();
 for(Role role : roleList){
 System.out.println(role);
 }
 System.out.println("----------------------------------");
}
           



        

            

        	





    

		

            
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