在不使用任何库(如@Transactional)的情况下在java中实现事务

Question

我有一个简单的应用程序，它执行以下操作：-

1. 从一个账户提款
2. 存入另一个账户

private void transfer(fromAccount,toAccount, amount){
fromAccount.withdraw(amount);
toAccount.deposit(amount);
}

如果不在事务上下文中运行，上述实现是相当危险的。如何在不使用任何库或@Transactional的情况下实现事务。

Answer 1

public class YourClass() { 
private void transfer(fromAccount,toAccount, amount) {
Account fromAccountObj = new Account(fromAccount);
Account toAccountObj = new Account(toAccount);
synchronized(fromAccountObj) { 
fromAccount.withdraw(amount);
}
synchronized(toAccountObj) { 
toAccount.deposit(amount);
}
}
}
public class Account {
private String accountNumber;
public Account(String accountNumber) {
this.accountNumber = accountNumber;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Account account = (Account) o;
return accountNumber.equals(account.accountNumber);
}
@Override
public int hashCode() {
return Objects.hash(accountNumber);
}
}

确保您的等号和哈希码为相同帐号的 n 个对象返回相同的值

Answer 2

private void transfer(fromAccount,toAccount, amount){ 
boolean withdrawn = false;
try {
fromAccount.withdraw(amount);
withdrawn = true;
toAccount.deposit(amount); 
} catch(Exception e) {
if(withdrawn)
fromAccount.deposit(amount);
// you can throw another Exception here, otherwise you just fail silently
}
}

此解决方案假设提款检查请求的金额是否可用，如果不可用，则引发异常。