Mybatis一对一延迟加载实现过程解析

2023-07-13 07:30:03 62

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

packagecom.yl.bean;

importjava.io.Serializable;
importjava.sql.Date;
importjava.util.List;

/**
*用户实体类
*/
publicclassUserimplementsSerializable{
privateIntegerid;//id
privateStringusername;//用户名
privateDatebirthday;//生日
privateStringsex;//性别
privateStringaddress;//地址
privateAccountaccount;//用户所拥有的账户

publicUser(){
}

publicIntegergetId(){
returnid;
}

publicvoidsetId(Integerid){
this.id=id;
}

publicStringgetUsername(){
returnusername;
}

publicvoidsetUsername(Stringusername){
this.username=username;
}

publicDategetBirthday(){
returnbirthday;
}

publicvoidsetBirthday(Datebirthday){
this.birthday=birthday;
}

publicStringgetSex(){
returnsex;
}

publicvoidsetSex(Stringsex){
this.sex=sex;
}

publicStringgetAddress(){
returnaddress;
}

publicvoidsetAddress(Stringaddress){
this.address=address;
}

publicAccountgetAccount(){
returnaccount;
}

publicvoidsetAccount(Accountaccount){
this.account=account;
}

@Override
publicStringtoString(){
return"User{"+
"id="+id+
",username='"+username+'\''+
",birthday="+birthday+
",sex='"+sex+'\''+
",address='"+address+'\''+
'}';
}
}

2、账户实体类

packagecom.yl.bean;

importjava.io.Serializable;

/**
*账户实体类
*/
publicclassAccountimplementsSerializable{
privateIntegerid;//账户id
privateIntegeruid;//用户id
privateDoublemoney;//余额
privateUseruser;//账户所属用户

publicAccount(){
}

publicIntegergetId(){
returnid;
}

publicvoidsetId(Integerid){
this.id=id;
}

publicIntegergetUid(){
returnuid;
}

publicvoidsetUid(Integeruid){
this.uid=uid;
}

publicDoublegetMoney(){
returnmoney;
}

publicvoidsetMoney(Doublemoney){
this.money=money;
}

publicUsergetUser(){
returnuser;
}

publicvoidsetUser(Useruser){
this.user=user;
}

@Override
publicStringtoString(){
return"Account{"+
"id="+id+
",uid="+uid+
",money="+money+
'}';
}
}

3、用户持久层接口

packagecom.yl.dao;

importcom.yl.bean.User;

importjava.util.List;

/**
*用户持久层接口
*/
publicinterfaceIUserDao{

/**
*查询所有用户
*/
ListqueryAll();

/**
*根据id查询用户
*/
UserqueryById(intid);

}

4、账户持久层接口

packagecom.yl.dao;

importcom.yl.bean.Account;
importcom.yl.bean.User;

importjava.util.List;

/**
*账户持久层接口
*/
publicinterfaceIAccountDao{

/**
*查询所有账户
*/
ListqueryAll();
}

5、全局配置文件

6、用户映射配置文件






















SELECT*FROMUSERuLEFTOUTERJOINaccountaONu.`id`=a.`UID`



select*fromuserwhereid=#{id}

7、账户映射配置文件
















SELECT*FROMaccount

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Mybatis一对一延迟加载实现过程解析

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