Java实现账户转账功能_模拟银行交易逻辑完整流程

public class Account {
    private String accountId;
    private double balance;
<pre class='brush:java;toolbar:false;'>public Account(String accountId, double balance) {
    this.accountId = accountId;
    this.balance = balance;
}

public synchronized void deposit(double amount) {
    if (amount <= 0) throw new IllegalArgumentException("存款金额必须大于0");
    this.balance += amount;
}

public synchronized boolean withdraw(double amount) {
    if (amount <= 0) throw new IllegalArgumentException("取款金额必须大于0");
    if (balance < amount) return false;
    balance -= amount;
    return true;
}

public String getAccountId() {
    return accountId;
}

public double getBalance() {
    return balance;
}

public class TransferService {
<pre class='brush:java;toolbar:false;'>public boolean transfer(Account from, Account to, double amount) {
    if (amount <= 0) {
        throw new IllegalArgumentException("转账金额必须大于0");
    }

    // 避免死锁：按账户ID排序锁定
    Account first = from.getAccountId().compareTo(to.getAccountId()) < 0 ? from : to;
    Account second = from == first ? to : from;

    // 双重加锁，保证线程安全
    synchronized (first) {
        synchronized (second) {
            if (!from.withdraw(amount)) {
                return false; // 余额不足
            }
            to.deposit(amount);
            return true;
        }
    }
}

public class TransactionLog {
    private List<String> logs = new ArrayList<>();
<pre class='brush:java;toolbar:false;'>public void log(String msg) {
    logs.add(LocalDateTime.now() + " - " + msg);
}

public void rollback(Account from, Account to, double amount) {
    to.deposit(amount);   // 撤销到账
    from.withdraw(-amount); // 补回转出金额（注意方向）
    log("事务回滚: " + from.getAccountId() + " → " + to.getAccountId() + ", 金额:" + amount);
}

public void commit(String fromId, String toId, double amount) {
    log("转账成功: " + fromId + " → " + toId + ", 金额:" + amount);
}

public boolean transferWithLog(Account from, Account to, double amount, TransactionLog log) {
    if (amount <= 0) throw new IllegalArgumentException();
<pre class='brush:java;toolbar:false;'>Account first = from.getAccountId().compareTo(to.getAccountId()) < 0 ? from : to;
Account second = from == first ? to : from;

synchronized (first) {
    synchronized (second) {
        boolean success = from.withdraw(amount);
        if (!success) {
            log.log("转账失败：余额不足 - " + from.getAccountId());
            return false;
        }
        to.deposit(amount);

        try {
            // 模拟网络延迟或中间错误
            // 若发生异常应触发回滚（实际中可用try-catch-finally或AOP）
            log.commit(from.getAccountId(), to.getAccountId(), amount);
            return true;
        } catch (Exception e) {
            log.rollback(from, to, amount);
            return false;
        }
    }
}

public class TransferTest {
    public static void main(String[] args) {
        Account accA = new Account("A001", 1000);
        Account accB = new Account("B002", 500);
        TransactionLog log = new TransactionLog();
        TransferService service = new TransferService();
<pre class='brush:java;toolbar:false;'>    // 正常转账
    boolean result = service.transferWithLog(accA, accB, 200, log);
    System.out.println("转账结果: " + result);
    System.out.println("A余额: " + accA.getBalance()); // 800
    System.out.println("B余额: " + accB.getBalance()); // 700

    // 余额不足
    result = service.transferWithLog(accA, accB, 900, log);
    System.out.println("二次转账结果: " + result); // false
}