Mybatis（一對一、一對多、多對多）操作
阿新 • • 發佈：2020-09-11
* 首先列出示例中用到的資料庫表
user表：
accout表：
role表：
user_role表：
建表語句如下：
DROP TABLE IF EXISTS `user`; CREATE TABLE `user` ( `id` int(11) NOT NULL auto_increment, `username` varchar(32) NOT NULL COMMENT '使用者名稱稱', `birthday` datetime default NULL COMMENT '生日', `sex` char(1) default NULL COMMENT '上述建表語句性別', `address` varchar(256) default NULL COMMENT '地址', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; insert into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(42,'小二王','2018-03-02 15:09:37','女','北京金燕龍'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龍'),(45,'傳智播客','2018-03-04 12:04:06','男','北京金燕龍'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小馬寶莉','2018-03-08 11:44:00','女','北京修正'); DROP TABLE IF EXISTS `account`; CREATE TABLE `account` ( `ID` int(11) NOT NULL COMMENT '編號', `UID` int(11) default NULL COMMENT '使用者編號', `MONEY` double defaultNULL COMMENT '金額', PRIMARY KEY (`ID`), KEY `FK_Reference_8` (`UID`), CONSTRAINT `FK_Reference_8` FOREIGN KEY (`UID`) REFERENCES `user` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; insert into `account`(`ID`,`UID`,`MONEY`) values (1,41,1000),(2,45,1000),(3,41,2000); DROP TABLE IF EXISTS `role`; CREATE TABLE `role` ( `ID` int(11) NOT NULL COMMENT '編號', `ROLE_NAME` varchar(30) default NULL COMMENT '角色名稱', `ROLE_DESC` varchar(60) default NULL COMMENT '角色描述', PRIMARY KEY (`ID`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; insert into `role`(`ID`,`ROLE_NAME`,`ROLE_DESC`) values (1,'院長','管理整個學院'),(2,'總裁','管理整個公司'),(3,'校長','管理整個學校'); DROP TABLE IF EXISTS `user_role`; CREATE TABLE `user_role` ( `UID` int(11) NOT NULL COMMENT '使用者編號', `RID` int(11) NOT NULL COMMENT '角色編號', PRIMARY KEY (`UID`,`RID`), KEY `FK_Reference_10` (`RID`), CONSTRAINT `FK_Reference_10` FOREIGN KEY (`RID`) REFERENCES `role` (`ID`), CONSTRAINT `FK_Reference_9` FOREIGN KEY (`UID`) REFERENCES `user` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; insert into `user_role`(`UID`,`RID`) values (41,1),(45,1),(41,2);
一、一對一操作（賬戶表[account]和使用者表[user]之間）
java專案目錄結構
前提：使用者表和賬戶表之間存在外來鍵關係。一個使用者可以擁有多個賬號，一個賬號只能被一個使用者擁有。
問題：如何查詢所有賬戶並將該賬戶的使用者資訊一同獲取到？
解析：一個賬戶只能存在一個使用者，因此為一對一關係。
1、在domain包下建立User實體類和Account實體類
User實體類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 import java.util.Date; 5 import java.util.List; 6 7 public class User implements Serializable { 8 private Integer id; 9 private String username; 10 private Date birthday; 11 private String sex; 12 private String address; 13 14 public Integer getId() { 15 return id; 16 } 17 18 public void setId(Integer id) { 19 this.id = id; 20 } 21 22 public String getUsername() { 23 return username; 24 } 25 26 public void setUsername(String username) { 27 this.username = username; 28 } 29 30 public Date getBirthday() { 31 return birthday; 32 } 33 34 public void setBirthday(Date birthday) { 35 this.birthday = birthday; 36 } 37 38 public String getSex() { 39 return sex; 40 } 41 42 public void setSex(String sex) { 43 this.sex = sex; 44 } 45 46 public String getAddress() { 47 return address; 48 } 49 50 public void setAddress(String address) { 51 this.address = address; 52 } 53 54 @Override 55 public String toString() { 56 return "User{" + 57 "id=" + id + 58 ", username='" + username + '\'' + 59 ", birthday=" + birthday + 60 ", sex='" + sex + '\'' + 61 ", address='" + address + '\'' + 62 '}'; 63 } 64 }User實體類
Account實體類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 5 /** 6 * @Classname Account 7 * @Description TODO 8 * @Date 2020/9/11 12:11 9 * @Created by Administrator 10 */ 11 public class Account implements Serializable { 12 private int id; 13 private int uid; 14 private double money; 15 // 用於封裝User物件 16 private User user; 17 18 public User getUser() { 19 return user; 20 } 21 22 public void setUser(User user) { 23 this.user = user; 24 } 25 26 public int getId() { 27 return id; 28 } 29 30 public void setId(int id) { 31 this.id = id; 32 } 33 34 public int getUid() { 35 return uid; 36 } 37 38 public void setUid(int uid) { 39 this.uid = uid; 40 } 41 42 public double getMoney() { 43 return money; 44 } 45 46 public void setMoney(double money) { 47 this.money = money; 48 } 49 50 @Override 51 public String toString() { 52 return "Account{" + 53 "id=" + id + 54 ", uid=" + uid + 55 ", money=" + money + 56 '}'; 57 } 58 }Account實體類
由於查詢主體是賬戶表而且查詢結果要包含賬戶對應的使用者，因此在Account實體類中封裝User物件。
2、在dao包中建立AccountDao介面，定義查詢方法
1 package sun.dao; 2 3 import sun.domain.Account; 4 import sun.domain.AccountUser; 5 6 import java.util.List; 7 8 /** 9 * @Classname AccountDao 10 * @Description TODO 11 * @Date 2020/9/11 13:13 12 * @Created by Administrator 13 */ 14 public interface AccountDao { 15 /** 16 * 查詢所有賬戶資訊和該賬戶的所屬者 17 */ 18 List<Account> findAll(); 19 20 }AccountDao介面
3、配置AccountDao.xml對映檔案
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE mapper 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 5 6 <mapper namespace="sun.dao.AccountDao"> 7 <!--封裝Account類--> 8 <resultMap id="accountUserMap" type="account"> 9 <id property="id" column="aid"></id> 10 <result property="uid" column="uid"></result> 11 <result property="money" column="money"></result> 12 <!--封裝User物件--> 13 <!--javaType指的是封裝物件型別--> 14 <association property="user" column="uid" javaType="user"> 15 <id property="id" column="id"></id> 16 <result property="username" column="username"></result> 17 <result property="sex" column="sex"></result> 18 <result property="address" column="address"></result> 19 <result property="birthday" column="birthday"></result> 20 </association> 21 </resultMap> 22 23 <!--查詢所有--> 24 <select id="findAll" resultMap="accountUserMap"> 25 <!--SELECT * from account;--> 26 SELECT u.*,a.id as aid,a.uid,a.money from user u,account a where a.uid=u.id 27 </select> 28 29 <select id="findAllAccount" resultType="accountuser"> 30 SELECT a.*,u.username,u.address from user u,account a where a.uid=u.id 31 </select> 32 </mapper>AccountDao.xml
4、AccountTest測試類進行查詢測試
1 package sun.test; 2 3 4 import org.apache.ibatis.io.Resources; 5 import org.apache.ibatis.session.SqlSession; 6 import org.apache.ibatis.session.SqlSessionFactory; 7 import org.apache.ibatis.session.SqlSessionFactoryBuilder; 8 import org.junit.After; 9 import org.junit.Before; 10 import org.junit.Test; 11 import org.omg.CORBA.PUBLIC_MEMBER; 12 import sun.dao.AccountDao; 13 import sun.dao.UserDao; 14 import sun.domain.Account; 15 import sun.domain.AccountUser; 16 import sun.domain.User; 17 18 import java.io.IOException; 19 import java.io.InputStream; 20 import java.util.List; 21 22 public class AccountTest { 23 24 private InputStream in; 25 private SqlSession sqlSession; 26 private AccountDao accountDao; 27 28 @Before 29 public void init() throws IOException { 30 // 讀取配置檔案 31 in = Resources.getResourceAsStream("SqlMapConfig.xml"); 32 // 建立SqlSessionFactory 33 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); 34 SqlSessionFactory factory = builder.build(in); 35 // 使用工廠生產sqlsession物件 36 sqlSession = factory.openSession(); 37 // 使用sqlsession建立UserDao介面代理物件 38 accountDao = sqlSession.getMapper(AccountDao.class); 39 } 40 41 @After 42 public void destory() throws IOException { 43 sqlSession.commit(); 44 sqlSession.close(); 45 in.close(); 46 } 47 48 @Test 49 public void findAllTest() { 50 // 使用代理物件執行方法 51 List<Account> all = accountDao.findAll(); 52 for (Account account : all) { 53 System.out.println("----------------"); 54 System.out.println(account); 55 System.out.println(account.getUser()); 56 } 57 } 58 @Test 59 public void findAllAccountTest(){ 60 List<AccountUser> allAcount = accountDao.findAllAccount(); 61 for (AccountUser accountUser : allAcount) { 62 System.out.println(accountUser); 63 } 64 } 65 66 }AccountTest測試類
測試結果：
二、一對多操作（使用者表[user]和賬戶表[account]之間）
java專案目錄結構
前提：使用者表和賬戶表之間存在外來鍵關係。一個使用者可以擁有多個賬號，一個賬號只能被一個使用者擁有。
問題：如何查詢所有使用者並將該使用者的所有賬號資訊一同獲取到？
解析：一個使用者可以擁有多個賬號，因此為一對多關係。
1、在domain包下建立User實體類和Account實體類
User類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 import java.util.Date; 5 import java.util.List; 6 7 public class User implements Serializable { 8 private Integer id; 9 private String username; 10 private Date birthday; 11 private String sex; 12 private String address; 13 // 封裝該實體所擁有的賬戶物件 14 private List<Account> accounts; 15 16 public List<Account> getAccounts() { 17 return accounts; 18 } 19 20 public void setAccounts(List<Account> accounts) { 21 this.accounts = accounts; 22 } 23 24 public Integer getId() { 25 return id; 26 } 27 28 public void setId(Integer id) { 29 this.id = id; 30 } 31 32 public String getUsername() { 33 return username; 34 } 35 36 public void setUsername(String username) { 37 this.username = username; 38 } 39 40 public Date getBirthday() { 41 return birthday; 42 } 43 44 public void setBirthday(Date birthday) { 45 this.birthday = birthday; 46 } 47 48 public String getSex() { 49 return sex; 50 } 51 52 public void setSex(String sex) { 53 this.sex = sex; 54 } 55 56 public String getAddress() { 57 return address; 58 } 59 60 public void setAddress(String address) { 61 this.address = address; 62 } 63 64 @Override 65 public String toString() { 66 return "User{" + 67 "id=" + id + 68 ", username='" + username + '\'' + 69 ", birthday=" + birthday + 70 ", sex='" + sex + '\'' + 71 ", address='" + address + '\'' + 72 '}'; 73 } 74 }User實體類
Account類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 5 /** 6 * @Classname Account 7 * @Description TODO 8 * @Date 2020/9/11 12:11 9 * @Created by Administrator 10 */ 11 public class Account implements Serializable { 12 private int id; 13 private int uid; 14 private double money; 15 16 public int getId() { 17 return id; 18 } 19 20 public void setId(int id) { 21 this.id = id; 22 } 23 24 public int getUid() { 25 return uid; 26 } 27 28 public void setUid(int uid) { 29 this.uid = uid; 30 } 31 32 public double getMoney() { 33 return money; 34 } 35 36 public void setMoney(double money) { 37 this.money = money; 38 } 39 40 @Override 41 public String toString() { 42 return "Account{" + 43 "id=" + id + 44 ", uid=" + uid + 45 ", money=" + money + 46 '}'; 47 } 48 }Account實體類
由於查詢主體是使用者表而且查詢結果要包含該使用者的所有賬號資訊，因此在User實體類中封裝List<Account>集合物件。
2、在dao包中建立UserDao介面，定義查詢方法
1 package sun.dao; 2 3 import sun.domain.User; 4 5 import java.util.List; 6 7 public interface UserDao { 8 /** 9 * 查詢所有使用者和該使用者名稱下的賬戶資訊 10 * @return 11 */ 12 List<User> findAll(); 13 14 }UserDao介面
3、配置UserDao.xml對映檔案
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE mapper 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 5 6 <mapper namespace="sun.dao.UserDao"> 7 <resultMap id="userAccountMap" type="user"> 8 <id property="id" column="id"></id> 9 <result property="username" column="username"></result> 10 <result property="sex" column="sex"></result> 11 <result property="birthday" column="birthday"></result> 12 <result property="address" column="address"></result> 13 <!--封裝使用者名稱下的賬戶資訊--> 14 <collection property="accounts" ofType="account"> 15 <id property="id" column="aid"></id> 16 <result property="uid" column="uid"></result> 17 <result property="money" column="money"></result> 18 </collection> 19 </resultMap> 20 21 <!--查詢所有--> 22 <select id="findAll" resultMap="userAccountMap"> 23 SELECT u.*,a.id as aid,a.uid,a.money FROM USER u LEFT OUTER JOIN account a ON u.id=a.uid 24 </select> 25 </mapper>UserDao.xml
4、UserTest測試類進行查詢測試
1 package sun.test; 2 3 4 import org.apache.ibatis.io.Resources; 5 import org.apache.ibatis.session.SqlSession; 6 import org.apache.ibatis.session.SqlSessionFactory; 7 import org.apache.ibatis.session.SqlSessionFactoryBuilder; 8 import org.junit.After; 9 import org.junit.Before; 10 import org.junit.Test; 11 import sun.dao.UserDao; 12 import sun.domain.User; 13 14 import java.io.IOException; 15 import java.io.InputStream; 16 import java.util.Date; 17 import java.util.List; 18 19 public class UserTest { 20 21 private InputStream in; 22 private SqlSession sqlSession; 23 private UserDao userDao; 24 25 @Before 26 public void init() throws IOException { 27 // 讀取配置檔案 28 in = Resources.getResourceAsStream("SqlMapConfig.xml"); 29 // 建立SqlSessionFactory 30 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); 31 SqlSessionFactory factory = builder.build(in); 32 // 使用工廠生產sqlsession物件 33 sqlSession = factory.openSession(); 34 // 使用sqlsession建立UserDao介面代理物件 35 userDao = sqlSession.getMapper(UserDao.class); 36 } 37 38 @After 39 public void destory() throws IOException { 40 sqlSession.commit(); 41 sqlSession.close(); 42 in.close(); 43 } 44 45 @Test 46 public void findAllTest() { 47 // 使用代理物件執行方法 48 List<User> all = userDao.findAll(); 49 for (User user : all) { 50 System.out.println("---------------"); 51 System.out.println(user); 52 System.out.println(user.getAccounts()); 53 } 54 } 55 56 }UserTest測試類
測試結果：
三、多對多操作（使用者表[user]和角色表[role]之間）
java專案目錄結構
前提：使用者表和角色表屬於多對多關係。
問題：如何查詢所有使用者並且返回每個使用者的所有角色資訊？
解析：一個使用者可以有多個角色，一個角色可以被多個使用者擁有，因此為多對多關係。（由於是多對多關係只測試一種就可，另一種相同方式）
1、在domain包下建立User實體類和Role實體類
User類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 import java.util.Date; 5 import java.util.List; 6 7 public class User implements Serializable { 8 private Integer id; 9 private String username; 10 private Date birthday; 11 private String sex; 12 private String address; 13 private List<Role> roles; 14 15 public List<Role> getRoles() { 16 return roles; 17 } 18 19 public void setRoles(List<Role> roles) { 20 this.roles = roles; 21 } 22 23 public Integer getId() { 24 return id; 25 } 26 27 public void setId(Integer id) { 28 this.id = id; 29 } 30 31 public String getUsername() { 32 return username; 33 } 34 35 public void setUsername(String username) { 36 this.username = username; 37 } 38 39 public Date getBirthday() { 40 return birthday; 41 } 42 43 public void setBirthday(Date birthday) { 44 this.birthday = birthday; 45 } 46 47 public String getSex() { 48 return sex; 49 } 50 51 public void setSex(String sex) { 52 this.sex = sex; 53 } 54 55 public String getAddress() { 56 return address; 57 } 58 59 public void setAddress(String address) { 60 this.address = address; 61 } 62 63 @Override 64 public String toString() { 65 return "User{" + 66 "id=" + id + 67 ", username='" + username + '\'' + 68 ", birthday=" + birthday + 69 ", sex='" + sex + '\'' + 70 ", address='" + address + '\'' + 71 '}'; 72 } 73 }User實體類
Role類：
1 package sun.domain; 2 3 import java.io.Serializable; 4 import java.util.List; 5 6 /** 7 * @Classname Role 8 * @Description TODO 9 * @Date 2020/9/11 14:51 10 * @Created by Administrator 11 */ 12 public class Role implements Serializable { 13 private int id; 14 private String roleName; 15 private String roleDesc; 16 private List<User> users; 17 18 public List<User> getUsers() { 19 return users; 20 } 21 22 public void setUsers(List<User> users) { 23 this.users = users; 24 } 25 26 public int getId() { 27 return id; 28 } 29 30 public void setId(int id) { 31 this.id = id; 32 } 33 34 public String getRoleName() { 35 return roleName; 36 } 37 38 public void setRoleName(String roleName) { 39 this.roleName = roleName; 40 } 41 42 public String getRoleDesc() { 43 return roleDesc; 44 } 45 46 public void setRoleDesc(String roleDesc) { 47 this.roleDesc = roleDesc; 48 } 49 50 @Override 51 public String toString() { 52 return "Role{" + 53 "id=" + id + 54 ", roleName='" + roleName + '\'' + 55 ", roleDesc='" + roleDesc + '\'' + 56 '}'; 57 } 58 }Role實體類
2、在dao包中建立RoleDao介面，定義查詢方法
1 package sun.dao; 2 3 import sun.domain.Role; 4 5 import java.util.List; 6 7 /** 8 * @Classname RoleDao 9 * @Description TODO 10 * @Date 2020/9/11 14:53 11 * @Created by Administrator 12 */ 13 public interface RoleDao { 14 /** 15 * 獲取所有角色記錄 16 * @return 17 */ 18 List<Role> findAll(); 19 }RoleDao介面
3、配置RoleDao.xml對映檔案
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE mapper 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 5 6 <mapper namespace="sun.dao.RoleDao"> 7 <resultMap id="roleMap" type="role"> 8 <id property="id" column="rid"></id> 9 <result property="roleName" column="role_name"></result> 10 <result property="roleDesc" column="role_desc"></result> 11 <!--封裝users--> 12 <collection property="users" ofType="user"> 13 <id property="id" column="id"></id> 14 <result property="username" column="username"></result> 15 <result property="sex" column="sex"></result> 16 <result property="birthday" column="birthday"></result> 17 <result property="address" column="address"></result> 18 </collection> 19 </resultMap> 20 21 <!--查詢所有--> 22 <select id="findAll" resultMap="roleMap"> 23 SELECT 24 u.*, 25 r.ID AS rid, 26 r.ROLE_NAME, 27 r.ROLE_DESC 28 FROM role r 29 LEFT OUTER JOIN user_role ur 30 ON r.ID = ur.RID 31 LEFT OUTER JOIN USER u 32 ON u.id = ur.UID 33 </select> 34 35 </mapper>RoleDao.xml
4、RoleTest測試類進行查詢測試
1 package sun.test; 2 3 4 import org.apache.ibatis.io.Resources; 5 import org.apache.ibatis.session.SqlSession; 6 import org.apache.ibatis.session.SqlSessionFactory; 7 import org.apache.ibatis.session.SqlSessionFactoryBuilder; 8 import org.junit.After; 9 import org.junit.Before; 10 import org.junit.Test; 11 import sun.dao.RoleDao; 12 import sun.dao.UserDao; 13 import sun.domain.Role; 14 import sun.domain.User; 15 16 import java.io.IOException; 17 import java.io.InputStream; 18 import java.util.Date; 19 import java.util.List; 20 21 public class MybatisTest { 22 23 private InputStream in; 24 private SqlSession sqlSession; 25 private RoleDao roleDao; 26 27 @Before 28 public void init() throws IOException { 29 // 讀取配置檔案 30 in = Resources.getResourceAsStream("SqlMapConfig.xml"); 31 // 建立SqlSessionFactory 32 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); 33 SqlSessionFactory factory = builder.build(in); 34 // 使用工廠生產sqlsession物件 35 sqlSession = factory.openSession(); 36 // 使用sqlsession建立UserDao介面代理物件 37 roleDao = sqlSession.getMapper(RoleDao.class); 38 } 39 40 @After 41 public void destory() throws IOException { 42 sqlSession.commit(); 43 sqlSession.close(); 44 in.close(); 45 } 46 47 @Test 48 public void findAllTest() { 49 // 使用代理物件執行方法 50 List<Role> all = roleDao.findAll(); 51 for (Role role : all) { 52 System.out.println("-------------"); 53 System.out.println(role); 54 System.out.println(role.getUsers()); 55 } 56 } 57 58 }RoleTest測試類
測試結果：