Mybatis一对一延迟加载实现过程解析
作者：Y_wee
这篇文章主要介绍了Mybatis一对一延迟加载实现过程解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
需求：用户和账户一对一关系，查询账户时实现用户的延迟加载
思路：根据id查询，需要延迟加载的一方
1、用户实体类
package com.yl.bean;
import java.io.Serializable;
import java.sql.Date;
import java.util.List;
/**
* 用户实体类
*/
public class User implements Serializable {
private Integer id;//id
private String username;//用户名
private Date birthday;//生日
private String sex;//性别
private String address;//地址
private Account account;//用户所拥有的账户
public User() {
}
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 Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Account getAccount() {
return account;
}
public void setAccount(Account account) {
this.account = account;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
2、账户实体类
package com.yl.bean;
import java.io.Serializable;
/**
* 账户实体类
*/
public class Account implements Serializable {
private Integer id;//账户id
private Integer uid;//用户id
private Double money;//余额
private User user;//账户所属用户
public Account() {
}
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;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String toString() {
return "Account{" +
"id=" + id +
", uid=" + uid +
", money=" + money +
'}';
}
}
3、用户持久层接口
package com.yl.dao;
import com.yl.bean.User;
import java.util.List;
/**
* 用户持久层接口
*/
public interface IUserDao {
/**
* 查询所有用户
*/
List<User> queryAll();
/**
* 根据id查询用户
*/
User queryById(int id);
}
4、账户持久层接口
package com.yl.dao;
import com.yl.bean.Account;
import com.yl.bean.User;
import java.util.List;
/**
* 账户持久层接口
*/
public interface IAccountDao {
/**
* 查询所有账户
*/
List<Account> queryAll();
}
5、全局配置文件
<?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>
<settings>
<!--开启延迟加载-->
<setting name="lazyLoadingEnabled" value="true"/>
<setting name="aggressiveLazyLoading" value="false"/>
</settings>
<!--配置别名-->
<typeAliases>
<package name="com.yl.bean"/>
</typeAliases>
<!--配置mybatis环境-->
<environments default="mysql">
<!--配置mysql环境-->
<environment id="mysql">
<!--事务类型-->
<transactionManager type="JDBC"></transactionManager>
<!--数据源-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf8&serverTimezone=GMT%2B8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!--指定映射配置文件位置-->
<mappers>
<mapper resource="IUserDao.xml"></mapper>
<mapper resource="IAccountDao.xml"></mapper>
</mappers>
</configuration>
6、用户映射配置文件
<?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.yl.dao.IUserDao">
<!--配置用户实体类和数据库的对应信息-->
<resultMap id="userMap" type="com.yl.bean.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>
<!--一对一映射关系-->
<collection property="account" ofType="com.yl.bean.Account">
<id property="id" column="id"></id>
<result property="uid" column="uid"></result>
<result property="money" column="money"></result>
</collection>
</resultMap>
<!--查询所有用户-->
<select id="queryAll" resultMap="userMap">
SELECT * FROM USER u LEFT OUTER JOIN account a ON u.`id`=a.`UID`
</select>
<!--根据id查询用户-->
<select id="queryById" resultType="user" parameterType="int">
select * from user where id=#{id}
</select>
</mapper>
7、账户映射配置文件
<?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.yl.dao.IAccountDao">
<!--配置Account属性对应数据库信息-->
<resultMap id="accountUserMap" type="account">
<id property="id" column="id"></id>
<result property="uid" column="uid"></result>
<result property="money" column="money"></result>
<!--通过id查询用户-->
<association property="user" column="uid" javaType="user" select="com.yl.dao.IUserDao.queryById"></association>
</resultMap>
<!--查询所有账户-->
<select id="queryAll" resultMap="accountUserMap">
SELECT * FROM account
</select>
</mapper>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。