Mybatis注解方式实现一对一，一对多的关联查询

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Mybatis注解方式实现一对一，一对多的关联查询

2023-10-13 18:17| 来源: 网络整理| 查看: 265

Step1 创建数据库表

使用Mysql WorkBench创建数据库表ssm20191229test,并创建table:user,book,addrss,如下: 在这里插入图片描述

Step2 创建maven工程

创建maven工程：mybatis20190103oneToOne，完整的结构目录如下：在这里插入图片描述

Step3 配置pom.xml和mybatis.xml

pom.xml代码如下：

4.0.0 com.mybatis mybatis20190102oneToOne 0.0.1-SNAPSHOT org.apache.maven.plugins maven-compiler-plugin 3.8.0 10 10 com.mybatis pomModule 0.0.1-SNAPSHOT

mybatis.xml配置如下：

Step4 创建pojo类

User.java

package com.cr.pojo; import java.util.List; public class User { private int userId; private String userName; private String userPassword; private int userAge; private String userEmail; private Address userAddress; private List books; public List getBooks() { return books; } public void setBooks(List books) { this.books = books; } public Address getAddress() { return userAddress; } public void setAddress(Address address) { this.userAddress = address; } public int getUserAge() { return userAge; } public void setUserAge(int userAge) { this.userAge = userAge; } public String getUserEmail() { return userEmail; } public void setUserEmail(String userEmail) { this.userEmail = userEmail; } public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public String getUserPassword() { return userPassword; } public void setUserPassword(String userPassword) { this.userPassword = userPassword; } }

Address.java

package com.cr.pojo; /** *

Title: Address.java

Description:

Company:uestc

* @author ChenRan * @date 2019年1月2日 * @version 1.0 */ public class Address { private int addressId; private String province; private String city; public int getAddressId() { return addressId; } public void setAddressId(int addressId) { this.addressId = addressId; } public String getProvince() { return province; } public void setProvince(String province) { this.province = province; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public String toString() { return this.province+this.city; } }

Book.java

package com.cr.pojo; public class Book { private int bookId; private String bookName; private int totalPage; private int price; public int getBookId() { return bookId; } public void setBookId(int bookId) { this.bookId = bookId; } public String getBookName() { return bookName; } public void setBookName(String bookName) { this.bookName = bookName; } public int getTotalPage() { return totalPage; } public void setTotalPage(int totalPage) { this.totalPage = totalPage; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } } Step5 创建mapper类

UserMapper.java

package com.cr.mapper; import org.apache.ibatis.annotations.Many; 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 com.cr.pojo.User; public interface UserMapper { //one to one @Select("select * from user where userId = #{userId}") @Results({ @Result(id=true,column="userId",property="userId"), @Result(column="userName",property="userName"), @Result(column="userPassword",property="userPassword"), @Result(column="userAge",property="userAge"), @Result(column="userEmail",property="userEmail"), @Result(column="userId",property="userAddress",one=@One(select="com.cr.mapper.AddressMapper.getAddressByUserId",fetchType= FetchType.EAGER)) }) public User getUserById(int userId); //one to many @Select("select * from user where userId=#{userId}") @Results({ @Result(id=true,column="userId",property="userId"), @Result(column="userName",property="userName"), @Result(column="userPassword",property="userPassword"), @Result(column="userAge",property="userAge"), @Result(column="userEmail",property="userEmail"), @Result(column="userId",property="books",many=@Many(select="com.cr.mapper.BookMapper.getBooksByUserId",fetchType= FetchType.EAGER)) }) public User getUserAndBooksById(int userId); }

AddressMapper.java

package com.cr.mapper; import org.apache.ibatis.annotations.Select; import com.cr.pojo.Address; public interface AddressMapper { @Select("select * from address where userId=#{userId}") public Address getAddressByUserId(int userId); }

BookMapper.java

package com.cr.mapper; import java.util.List; import org.apache.ibatis.annotations.Select; import com.cr.pojo.Book; public interface BookMapper { @Select("select * from book where userId = #{userId}") public List getBooksByUserId(int userId); } Step6 创建测试类

oneToOne.java

package com.cr.test; import java.io.Reader; 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 com.cr.mapper.UserMapper; import com.cr.pojo.User; public class OneToOne { private static SqlSessionFactory sqlSessionFactory; private static Reader reader; static { try { reader = Resources.getResourceAsReader("mybatis.xml"); sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); } catch (Exception e) { e.printStackTrace(); } } public static SqlSessionFactory getSession() { return sqlSessionFactory; } public static void main(String[] args) { test(4); } //测试模块 private static void test(int userId) { SqlSession session = sqlSessionFactory.openSession(); try { UserMapper userMapper = session.getMapper(UserMapper.class); User user = userMapper.getUserById(userId); if(user != null) { printUser(user); } else { System.out.println("userId为"+userId+"的用户不存在！可能未创建或者已经被删除。"); } } finally { session.close(); } } //输出用户信息 private static void printUser(User user) { System.out.println("用户id:"+user.getUserId()+"\n姓名：" +user.getUserName()+"\n年龄："+user.getUserAge() +"\n邮箱："+user.getUserEmail()+"\n地址："+user.getAddress().toString()); } }

oneToMany.java

package com.cr.test; import java.io.Reader; import java.util.List; 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 com.cr.mapper.UserMapper; import com.cr.pojo.Book; import com.cr.pojo.User; /** *

Title: oneToMany.java

Description:

Company:uestc

* @author ChenRan * @date 2019年1月2日 * @version 1.0 */ public class oneToMany { private static SqlSessionFactory sqlSessionFactory; private static Reader reader; static { try { reader = Resources.getResourceAsReader("mybatis.xml"); sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); } catch (Exception e) { e.printStackTrace(); } } public static SqlSessionFactory getSession() { return sqlSessionFactory; } /** * @param args */ public static void main(String[] args) { test(5); } private static void test(int userId) { SqlSession session = sqlSessionFactory.openSession(); try { UserMapper userMapper = session.getMapper(UserMapper.class); User user = userMapper.getUserAndBooksById(userId); if(user != null) { printUserAndBooks(user); } else { System.out.println("userId为"+userId+"的用户不存在！可能未创建或者已经被删除。"); } } finally { session.close(); } } private static void printUserAndBooks(User user) { System.out.println("用户id:"+user.getUserId()+"\n姓名：" +user.getUserName()+"\n年龄："+user.getUserAge() +"\n邮箱："+user.getUserEmail()); List books = user.getBooks(); String messsage = "喜欢的书籍："; for(Book book:books) { messsage = messsage+book.getBookName()+" "; } System.out.println(messsage); } } 结语

测试结果如下：运行oneToOne.java: 在这里插入图片描述运行oneToMany.java: 时间关系，写的比较简略。（2019.01.03）

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Mybatis注解方式实现一对一，一对多的关联查询

Mybatis注解方式实现一对一，一对多的关联查询

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