Mybatis实现一对多
项目结构
配置文件
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pom.xml
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.xiaoge</groupId> <artifactId>one2many</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <dependencies> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.5</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.13</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> </dependencies> </project> -
jdbcConfig.properties
jdbc.driver=com.mysql.cj.jdbc.Driver jdbc.url=jdbc:mysql://localhost:3306/eesy_mybatis jdbc.username=root jdbc.password=123456 -
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"> <configuration> <!--配置properties--> <properties resource="jdbcConfig.properties"> </properties> <!-- 使用typeAliases配置别名, 它只能配置domain中类的别名 --> <typeAliases> <package name="com.xiaoge.domain"></package> </typeAliases> <!--配置环境--> <environments default="mysql"> <!--配置mysql环境--> <environment id="mysql"> <!--配置事务--> <transactionManager type="JDBC"></transactionManager> <!--配置连接池--> <dataSource type="POOLED"> <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> <mappers> <package name="com.xiaoge.dao"></package> </mappers> </configuration> -
userDao.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.xiaoge.dao.UserDao"> <resultMap id="userAccountMap" type="user"> <id property="id" column="id"></id> <result property="username" column="username"></result> <result property="birthday" column="birthday"></result> <result property="sex" column="sex"></result> <result property="address" column="address"></result> <!-- 配置user对象中accounts集合的映射 --> <!-- ofType是指定accounts集合中元素的类型 我这里写Account是因为我去了别名的 --> <!-- 一切用到实体类的, 没取别名的就要使用全限定类名 --> <collection property="accounts" ofType="Account"> <!-- 我这里column写的是aid 注意我的sql语句 我给id取了个别名 --> <!-- property只能写实体类的属性 --> <id property="id" column="aid"></id> <result property="uid" column="uid"></result> <result property="money" column="money"></result> </collection> </resultMap> <!-- 查询所有用户操作(使用mybatis一对多映射关系) --> <select id="findAll" resultMap="userAccountMap"> select user.*, account.id as aid, account.uid as uid, account.money as money from user left join account on user.id = uid </select> </mapper>
实体类
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User
package com.xiaoge.domain; import java.util.Date; import java.util.List; /** * @Author: 潇哥 * @DateTime: 2020/3/4 下午4:03 * @Description: TODO */ public class User { private Integer id; private String username; private String address; private String sex; private Date birthday; // 一对多关系映射, 主表实体应该包含从表实体的集合引用 private List<Account> accounts; public List<Account> getAccounts() { return accounts; } public void setAccounts(List<Account> accounts) { this.accounts = accounts; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\'' + ", address='" + address + '\'' + ", sex='" + sex + '\'' + ", birthday=" + birthday + '}'; } } -
Account
package com.xiaoge.domain; /** * @Author: 潇哥 * @DateTime: 2020/3/16 下午6:02 * @Description: TODO */ public class Account { private Integer id; private Integer uid; private Double money; // 从表实体应该包含一个主表实体的对象引用 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 + '}'; } }
持久层接口
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UserDao
package com.xiaoge.dao; import com.xiaoge.domain.User; import java.util.List; /** * @Author: 潇哥 * @DateTime: 2020/3/4 下午4:19 * @Description: 用户的持久层接口 */ public interface UserDao { /** * 查询所有用户, 同时获取到用户下所有账户的信息 * @return */ public List<User> findAll(); }
测试持久层接口方法
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UserTest
package com.xiaoge.test; import com.xiaoge.dao.UserDao; import com.xiaoge.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: 潇哥 * @DateTime: 2020/3/16 下午6:12 * @Description: TODO */ public class UserTest { private SqlSession session; private UserDao userDao; private InputStream is; @Before public void init() throws IOException { is = Resources.getResourceAsStream("SqlMapConfig.xml"); SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); SqlSessionFactory factory = builder.build(is); session = factory.openSession(); userDao = session.getMapper(UserDao.class); } @After public void destroy() throws IOException { if (session != null) { session.commit(); session.close(); } if (is != null) { is.close(); } } /** * 测试查询所有 */ @Test public void findAllTest(){ List<User> list = userDao.findAll(); for (User user : list) { System.out.println("-----------每个user信息------------"); System.out.println(user); System.out.println(user.getAccounts()); } // 运行结果 -----------每个user信息------------ User{id=41, username='老王', address='北京', sex='男', birthday=Wed Feb 28 07:47:08 CST 2018} [Account{id=1, uid=41, money=1000.0}] -----------每个user信息------------ User{id=42, username='小二王', address='北京金燕龙', sex='女', birthday=Sat Mar 03 05:09:37 CST 2018} [Account{id=2, uid=42, money=1000.0}] -----------每个user信息------------ User{id=43, username='小二王', address='北京金燕龙', sex='女', birthday=Mon Mar 05 01:34:34 CST 2018} [Account{id=3, uid=43, money=2000.0}, Account{id=4, uid=43, money=3000.0}] -----------每个user信息------------ User{id=46, username='老王', address='北京', sex='女', birthday=Thu Mar 08 07:37:26 CST 2018} [] -----------每个user信息------------ User{id=48, username='小马宝莉', address='北京修正', sex='女', birthday=Fri Mar 09 01:44:00 CST 2018} [] -----------每个user信息------------ User{id=53, username='啸哥', address='北京四合院', sex='男', birthday=Fri Mar 06 13:10:42 CST 2020} [] -----------每个user信息------------ User{id=54, username='李四 last insertid', address='北京', sex='男', birthday=Fri Mar 06 14:26:40 CST 2020} [] -----------每个user信息------------ User{id=55, username='王五 last insertid', address='北京', sex='男', birthday=Fri Mar 06 15:17:43 CST 2020} [] -----------每个user信息------------ User{id=56, username='李六 last insertid', address='北京', sex='男', birthday=Fri Mar 06 18:47:48 CST 2020} [] -----------每个user信息------------ User{id=57, username='李六 last insertid', address='北京', sex='男', birthday=Fri Mar 06 19:11:40 CST 2020} [] -----------每个user信息------------ User{id=59, username='李白 last insertid', address='北京', sex='男', birthday=Wed Mar 11 18:17:20 CST 2020} [] } }
