java - 是什么让事务成为 Spring/Java 中的事务(特定场景)？

Question

我已经阅读了本网站上的交易定义以及其他一些外部资源。但在编写代码时，我很难理解事务的具体概念。

我有一个事务性的 BuyService 类。 BuyService 类被声明为事务性的，其唯一方法是 buyWidget(String widgetId)。此方法调用ExampleService 类，该类具有deleteWidgit(String widgetId) 方法。它还调用 InvoiceService 类，该类使用 writeInvoice(String widgitId) 方法。这是代码:

BuyService 类:

import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@Transactional
public class BuyService implements BuyServiceInterface
{
private ExampleServiceInterface exampleService;
private InvoiceServiceInterface invoiceService;

public void setExampleService(ExampleServiceInterface exampleService)
{
    this.exampleService = exampleService;
}

public void setInvoiceService(InvoiceServiceInterface invoiceService)
{
    this.invoiceService = invoiceService;
}

@Override
@Transactional(propagation=Propagation.REQUIRED)
public void buyWidget(Widget widgetId)
{
    try
    {
        Widget purchasedWidget = this.exampleService.getWidgetById(String widgetId);
        this.exampleService.deleteWidget(purchasedWidget);
        this.invoiceService.writeInvoice(purchasedWidget);
    }
    catch (WidgetNotFoundException e)
    {
        System.out.println("Widget with widgetId " + widgetId + " not found.");
    }
}
}

我非常确定 buyWidget 方法构成了一笔交易。它需要删除数据库(在 exampleService 中)中的小部件，并在购买数据库(在 invoiceService 中)中插入数据。但此后我对术语感到困惑。 deleteWidget 和 writeInvoice 方法本身也是事务吗？

示例服务类:

public class ExampleService implements ExampleServiceInterface
    {   
private ExampleServiceDaoInterface dao;

public void setExampleServiceDao(ExampleServiceDaoInterface dao)
{
    this.dao = dao;
}

@Override
public void deleteWidget(Widget oldWidget) 
        throws WidgetNotFoundException
{
    this.dao.delete(oldWidget);
}

@Override
public Widget getWidgetById(String widgetId)
{
    return this.dao.getById(widgetId);
}
}

发票服务类:

public class InvoiceService implements InvoiceServiceInterface
{   
private InvoiceServiceDaoInterface InvoiceServiceDao;

public void setInvoiceServiceDao(InvoiceServiceDaoInterface InvoiceServiceDao)
{
    this.InvoiceServiceDao = InvoiceServiceDao;
}

@Override
public void writeInvoice(Widget purchasedWidget)
{
    Date purchaseDate = new Date(new java.util.Date().getTime());
    String isbn = purchasedWidget.getIsbn();
    Purchases newPurchase = new Purchases(purchaseDate, isbn);
    this.InvoiceServiceDao.savePurchase(newPurchase);
}
} 

buyWidget 交易也会调用这两个方法吗？也就是说，即使这些方法都没有声明为事务。不将两个子方法声明为事务有哪些潜在的陷阱？ (因为它们显然已经成为其中的一部分)。

Answer 1

Are the methods deleteWidget and writeInvoice themselves transactions as well?

他们将参与 buyWidget 交易，但他们本身并不具有交易性

Are the two methods called on by buyWidget transactions as well?

事务在进入buyWidget方法之前启动，并在该方法完成之前停止或回滚。这两个方法将参与 buyWidget 交易，但它们本身并不是交易。