Mybatis注解开发多表一对一，一对多，

Mybatis注解开发多表一对一，一对多，

Mybatis注解开发多表一对一，一对多

---

一对一

示例：帐户和用户的对应关系为，多个帐户对应一个用户，在实际开发中，查询一个帐户并同时查询该账户所属的用户信息，即立即加载且在mybatis中表现为一对一的关系。应为账户的实体类Account中添加User为一个属性。

实体类：User，Account

User

 package com.itheima.domain;
 ​
 import java.io.Serializable;
 import java.util.Date;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 21:37 2020/2/22
  * @Modified By:
  */
 public class User implements Serializable {
     private Integer userId;
     private String userName;
     private Date userBirthday;
     private String userSex;
     private String userAddress;
 ​
     public Integer getUserId() {
         return userId;
     }
 ​
     public void setUserId(Integer userId) {
         this.userId = userId;
     }
 ​
     public String getUserName() {
         return userName;
     }
 ​
     public void setUserName(String userName) {
         this.userName = userName;
     }
 ​
     public Date getUserBirthday() {
         return userBirthday;
     }
 ​
     public void setUserBirthday(Date userBirthday) {
         this.userBirthday = userBirthday;
     }
 ​
     public String getUserSex() {
         return userSex;
     }
 ​
     public void setUserSex(String userSex) {
         this.userSex = userSex;
     }
 ​
     public String getUserAddress() {
         return userAddress;
     }
 ​
     public void setUserAddress(String userAddress) {
         this.userAddress = userAddress;
     }
 ​
     @Override
     public String toString() {
         return "User{" +
                 "userId=" + userId +
                 ", userName='" + userName + '\'' +
                 ", userBirthday=" + userBirthday +
                 ", userSex='" + userSex + '\'' +
                 ", userAddress='" + userAddress + '\'' +
                 '}';
     }
 }
 ​

Account

 package com.itheima.domain;
 ​
 import java.io.Serializable;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 14:09 2020/2/28
  * @Modified By:
  */
 public class Account implements Serializable {
 ​
     private Integer id;
     private Integer uid;
     private Double money;
 ​
     //多对一，mybatis中称之为一对一的映射：一个账户只能属于一个用户
     private User user;
 ​
     public User getUser() {
         return user;
     }
 ​
     public void setUser(User user) {
         this.user = user;
     }
 ​
     public Integer getId() {
         return id;
     }
 ​
     public void setId(Integer id) {
         this.id = id;
     }
 ​
     public Integer getUid() {
         return uid;
     }
 ​
     public void setUid(Integer uid) {
         this.uid = uid;
     }
 ​
     public Double getMoney() {
         return money;
     }
 ​
     public void setMoney(Double money) {
         this.money = money;
     }
 ​
     @Override
     public String toString() {
         return "Account{" +
                 "id=" + id +
                 ", uid=" + uid +
                 ", money=" + money +
                 '}';
     }
 }
 ​

接口：IUserDao，IAccountDao

IUserDao

 package com.itheima.dao;
 ​
 import com.itheima.domain.User;
 import org.apache.ibatis.annotations.*;
 ​
 import java.beans.IntrospectionException;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description: 用户的持久层接口
  * @Data: Create in 21:42 2020/2/22
  * @Modified By:
  */
 public interface IUserDao {
 ​
     //查询所有用户，同时获取到用户下所有账户的信息
     @Select("select * from user")
     //当实体类的属性和数据库的属性名称不一致时，需要配置对应关系，id为该Results的唯一标识
     @Results(id = "userMap", value={
             @Result(id=true,column = "id",property = "userId"),
             @Result(column = "username",property = "userName"),
             @Result(column = "sex",property = "userSex"),
             @Result(column = "address",property = "userAddress"),
             @Result(column = "birthday",property = "userBirthday"),
     })
     List<User> findAll();
 ​
     @Insert("Insert into user (username,address,sex,birthday) values (#{username},#{address},#{sex},#{birthday})")
     void  saveUser(User user);
 ​
     @Update("update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id = #{id}")
     void updateUser(User user);
 ​
     @Delete("delete from user where id = #{id}")
     void deleteUser(Integer integer);
 ​
     @Select("select * from user where id = #{id}")
     @ResultMap(value = {"userMap"})
     User findById(Integer integer);
 ​
     @Select("Select * from user where username like #{username}")
     @ResultMap(value = {"userMap"})
     List<User> findUserByName(String username);
 ​
 }
 ​

IAccountDao

 package com.itheima.dao;
 ​
 import com.itheima.domain.Account;
 import org.apache.ibatis.annotations.One;
 import org.apache.ibatis.annotations.Result;
 import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.Select;
 import org.apache.ibatis.mapping.FetchType;
 ​
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 14:10 2020/2/28
  * @Modified By:
  */
 public interface IAccountDao {
 ​
     /**
      * @Author Lijiahao
      * @Description 查询所有帐户，并且获取每个帐户所属的用户信息
      * @Date 14:11 2020/2/28
      * @Param []
      * @return List<Account>
      **/
     @Select("select * from account")
     @Results(id="accountMap",value = {
             //封装account
             @Result(id = true , column = "id" ,property = "id"),
             @Result(column = "uid" ,property = "uid"),
             @Result(column = "money" ,property = "money"),
             //封装user，account-user 是一对一关系
             @Result(property = "user",column = "uid",one = @One(select="com.itheima.dao.IUserDao.findById",fetchType = FetchType.EAGER))
     })
     List<Account> findAll();
 }
 ​

配置文件：主配置文件，日志，连接池

主配置文件：SqlMapConfig.xml

 <?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">
 ​
 <!--mybatis的主配置文件-->
 <configuration>
 ​
     <properties resource="jdbcConfig.properties"/>
 ​
     <!--配置别名 类名就是别名，不区分大小写-->
     <typeAliases>
         <package name="com.itheima.domain" ></package>
     </typeAliases>
 ​
     <!--配置环境-->
     <environments default="mysql">
         <!--配置mysql的环境-->
         <environment id="mysql">
             <!--配置事务的类型-->
             <transactionManager type="JDBC"></transactionManager>
             <!--配置数据源（连接池）-->
             <dataSource type="POOLED">
                 <!--配置数据库的四个基本信息-->
                 <property name="driver" value="${jdbc.driver}" />
                 <property name="url" value="${jdbc.url}"/>
                 <property name="username" value="${jdbc.username}" />
                 <property name="password" value="${jdbc.password}" />
             </dataSource>
         </environment>
     </environments>
 ​
     <!--指定dao接口所在位置-->
     <mappers>
         <package name="com.itheima.dao"></package>
     </mappers>
 </configuration>

测试

 package com.itheima;
 ​
 import com.itheima.dao.IAccountDao;
 import com.itheima.dao.IUserDao;
 import com.itheima.domain.Account;
 import com.itheima.domain.User;
 import org.apache.ibatis.io.Resources;
 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 ​
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 22:56 2020/2/22
  * @Modified By:
  */
 public class AccountTest {
     private InputStream in;
     private SqlSession sqlSession;
     private IAccountDao iAccountDao;
     private SqlSessionFactory sqlSessionFactory;
 ​
     @Before
     public void init() throws Exception {
         in = Resources.getResourceAsStream("SqlMapConfig.xml");
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
         sqlSession = sqlSessionFactory.openSession();
         iAccountDao = sqlSession.getMapper(IAccountDao.class);
     }
 ​
     @After
     public void destroy() throws IOException {
         sqlSession.commit();
         sqlSession.close();
         in.close();
     }
 ​
     @Test
     public void testFindAll() {
         List<Account> accounts = iAccountDao.findAll();
         for (Account account : accounts) {
             System.out.println("获取每个用户的信息");
             System.out.println(account);
             System.out.println(account.getUser());
         }
 ​
     }
 }

---

一对多

示例：用户user-帐户Account是一对多的关系，在mybatis中也是一对多的关系，即使用延迟加载且在user类中添加实体类Account的属性。

实体类：User，Account

User

 package com.itheima.domain;
 ​
 import java.io.Serializable;
 import java.util.Date;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 21:37 2020/2/22
  * @Modified By:
  */
 public class User implements Serializable {
     private Integer userId;
     private String userName;
     private Date userBirthday;
     private String userSex;
     private String userAddress;
 ​
     //一对多关系映射，一个用户对应多个账户
     private List<Account> accounts;
 ​
     public List<Account> getAccounts() {
         return accounts;
     }
 ​
     public void setAccounts(List<Account> accounts) {
         this.accounts = accounts;
     }
 ​
     public Integer getUserId() {
         return userId;
     }
 ​
     public void setUserId(Integer userId) {
         this.userId = userId;
     }
 ​
     public String getUserName() {
         return userName;
     }
 ​
     public void setUserName(String userName) {
         this.userName = userName;
     }
 ​
     public Date getUserBirthday() {
         return userBirthday;
     }
 ​
     public void setUserBirthday(Date userBirthday) {
         this.userBirthday = userBirthday;
     }
 ​
     public String getUserSex() {
         return userSex;
     }
 ​
     public void setUserSex(String userSex) {
         this.userSex = userSex;
     }
 ​
     public String getUserAddress() {
         return userAddress;
     }
 ​
     public void setUserAddress(String userAddress) {
         this.userAddress = userAddress;
     }
 ​
     @Override
     public String toString() {
         return "User{" +
                 "userId=" + userId +
                 ", userName='" + userName + '\'' +
                 ", userBirthday=" + userBirthday +
                 ", userSex='" + userSex + '\'' +
                 ", userAddress='" + userAddress + '\'' +
                 '}';
     }
 }
 ​

Account

 package com.itheima.domain;
 ​
 import java.io.Serializable;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 14:09 2020/2/28
  * @Modified By:
  */
 public class Account implements Serializable {
 ​
     private Integer id;
     private Integer uid;
     private Double money;
 ​
     //多对一，mybatis中称之为一对一的映射：一个账户只能属于一个用户
     private User user;
 ​
     public User getUser() {
         return user;
     }
 ​
     public void setUser(User user) {
         this.user = user;
     }
 ​
     public Integer getId() {
         return id;
     }
 ​
     public void setId(Integer id) {
         this.id = id;
     }
 ​
     public Integer getUid() {
         return uid;
     }
 ​
     public void setUid(Integer uid) {
         this.uid = uid;
     }
 ​
     public Double getMoney() {
         return money;
     }
 ​
     public void setMoney(Double money) {
         this.money = money;
     }
 ​
     @Override
     public String toString() {
         return "Account{" +
                 "id=" + id +
                 ", uid=" + uid +
                 ", money=" + money +
                 '}';
     }
 }
 ​

接口：IUserDao，IAccountDao

IUserDao

 package com.itheima.dao;
 ​
 import com.itheima.domain.User;
 import org.apache.ibatis.annotations.*;
 import org.apache.ibatis.mapping.FetchType;
 ​
 import javax.xml.parsers.FactoryConfigurationError;
 import java.beans.IntrospectionException;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description: 用户的持久层接口
  * @Data: Create in 21:42 2020/2/22
  * @Modified By:
  */
 public interface IUserDao {
 ​
     //查询所有用户，同时获取到用户下所有账户的信息
     @Select("select * from user")
     //当实体类的属性和数据库的属性名称不一致时，需要配置对应关系，id为该Results的唯一标识
     @Results(id = "userMap", value={
             @Result(id=true,column = "id",property = "userId"),
             @Result(column = "username",property = "userName"),
             @Result(column = "sex",property = "userSex"),
             @Result(column = "address",property = "userAddress"),
             @Result(column = "birthday",property = "userBirthday"),
             //配置user-account的一对多的配置
             @Result(column = "id",property = "accounts",
                     many=@Many(select = "com.itheima.dao.IAccountDao.findAccountByUid",
                             fetchType= FetchType.LAZY))
     })
     List<User> findAll();
 ​
     @Insert("Insert into user (username,address,sex,birthday) values (#{username},#{address},#{sex},#{birthday})")
     void  saveUser(User user);
 ​
     @Update("update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id = #{id}")
     void updateUser(User user);
 ​
     @Delete("delete from user where id = #{id}")
     void deleteUser(Integer integer);
 ​
     @Select("select * from user where id = #{id}")
     @ResultMap(value = {"userMap"})
     User findById(Integer integer);
 ​
     @Select("Select * from user where username like #{username}")
     @ResultMap(value = {"userMap"})
     List<User> findUserByName(String username);
 ​
 }
 ​

IAccountDao

 package com.itheima.dao;
 ​
 import com.itheima.domain.Account;
 import org.apache.ibatis.annotations.One;
 import org.apache.ibatis.annotations.Result;
 import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.Select;
 import org.apache.ibatis.mapping.FetchType;
 ​
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 14:10 2020/2/28
  * @Modified By:
  */
 public interface IAccountDao {
 ​
     /**
      * @Author Lijiahao
      * @Description 查询所有帐户，并且获取每个帐户所属的用户信息
      * @Date 14:11 2020/2/28
      * @Param []
      * @return List<Account>
      **/
     @Select("select * from account")
     @Results(id="accountMap",value = {
             //封装account
             @Result(id = true , column = "id" ,property = "id"),
             @Result(column = "uid" ,property = "uid"),
             @Result(column = "money" ,property = "money"),
             //封装user，account-user 是一对一关系
             @Result(property = "user",column = "uid",
                     one = @One(select="com.itheima.dao.IUserDao.findById",
                             fetchType = FetchType.EAGER))
     })
     List<Account> findAll();
 ​
     @Select("select * from account where uid = #{userId}")
     List<Account> findAccountByUid(Integer userId);
 }

测试

 package com.itheima;
 ​
 import com.itheima.dao.IUserDao;
 import com.itheima.domain.User;
 import org.apache.ibatis.io.Resources;
 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 ​
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Date;
 import java.util.List;
 ​
 /**
  * @Author: lijiahao
  * @Description:
  * @Data: Create in 22:56 2020/2/22
  * @Modified By:
  */
 public class UserTest {
     private InputStream in;
     private SqlSession sqlSession;
     private IUserDao iUserDao;
     private SqlSessionFactory sqlSessionFactory;
 ​
     @Before
     public void init() throws Exception {
         in = Resources.getResourceAsStream("SqlMapConfig.xml");
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
         sqlSession = sqlSessionFactory.openSession();
         iUserDao = sqlSession.getMapper(IUserDao.class);
     }
 ​
     @After
     public void destroy() throws IOException {
         sqlSession.commit();
         sqlSession.close();
         in.close();
     }
 ​
     @Test
     public void testFindAll(){
         List<User> users = iUserDao.findAll();
         for(User user : users) {
             System.out.println(user);
             System.out.println(user.getAccounts());
         }
     }
 ​
     @Test
     public void testFindById(){
         User user = iUserDao.findById(57);
         System.out.println(user);
     }
 ​
     @Test
     public void testFindUserByName(){
         List<User> users = iUserDao.findUserByName("%王%");
         //List<User> users = iUserDao.findUserByName("王");
         for(User user : users)
             System.out.println(user);
     }
 ​
 }