将数据传递到表单时的Post-Redirect-Get? [英] Post-Redirect-Get when passing data to the form?

问题描述

在几种情况下，servlet需要从数据库中检索到的记录中将数据传递到JSP中的表单.目前，我正在使用RequestDispatcher将此信息存储在请求中，以转发至页面，一切正常.

I have several scenarios where a servlet needs to pass data to a form in a JSP from the retrieved records from the database. Currently, I'm storing this information in the request, using a RequestDispatcher to forward to the page, and all is well.

但是，这不适合PRG模式(AFAIK)，并且当然意味着刷新生成的JSP意味着重新运行servlet，这是不希望的.

However, this is not fitting with the PRG pattern (AFAIK), and of course means that refreshing of the resulting JSP means re-running of the servlet, which is undesirable.

我当然可以将这些值存储在会话中，但这意味着要在以后将其清除，即使使用会话，对于从数据库中显示记录似乎也有点可笑.

I could of course store these values in the session, but that would mean clearing them afterwards, and even using the session seems like a bit of a hack for displaying a record from the database.

我只是想知道在这种情况下最好的做法是什么?我应该继续使用请求，使用会话还是其他方法?

I am simply wondering what would be the best practice in this situation? Should I continue using the request, use the session, or some other technique?

谢谢.

修改: 在阅读了几篇文章并获得了堆栈溢出的答案之后，除了将请求的数据从servlet传递到JSP时，没有其他地方可以使用请求和分派器.对我来说似乎不对，但会议也不对.有人能对此有所启发吗?

After reading several articles and stack overflow answers, I can find nowhere that presents any other option than using the request and a dispatcher when passing data from a servlet to a JSP. It doesn't seem right to me, but neither does the session. Can anybody shed some light on this?

推荐答案

我不确定我是否完全理解该问题，但是两种模式是最佳实践:

I'm not sure I fully understand the problem, but two patterns are best practices:

1. 总是经过一个控制器，该控制器填充模型，将其存储在请求中，然后分派到一个视图，该视图在模型中显示数据.这就是MVC模式
2. 总是在成功的非幂等请求(即POST，如果遵守HTTP协议)之后重定向.那就是后重定向获取模式.

所以这意味着您应该拥有:

So what it means is that you should have:

• 请求1进入servlet.
• servlet获取要在表单中显示的数据并将其存储在请求中，然后转发到JSP
• JSP显示表单
• 将表单提交到servlet(请求2)
• servlet将数据存储在数据库中，该数据库将为创建的数据生成一个ID
• servlet重定向到/product?id=<generatedId>或/product/<generatedId>
之类的URL
• 浏览器向该URL发送一个请求(请求3).该请求发送到servlet
• servlet从数据库获取ID标识的数据.它将数据存储到请求中，然后转发到JSP
• JSP显示数据.

• request 1 goes to a servlet.
• servlet gets data to be displayed in the form and stores it in the request, then forwards to the JSP
• the JSP displays the form
• the form is submitted to a servlet (request 2)
• servlet stores the data in the database, which generates an ID for the created data
• servlet redirects to a URL like /product?id=<generatedId> or /product/<generatedId>
• browser sends a request to this URL (request 3). This request goes to a servlet
• servlet gets the data identified by the ID, from the database. It stores the data into the request, and forwards to a JSP
• the JSP displays the data.

当然，您可以选择重定向到其他页面，例如产品列表.

Of course, you could choose to redirect to some other page, like the list of products for example.

如果麻烦的是在从servlet传输到JSP时使用请求存储数据，那么这应该不会打扰您:这是唯一的干净方法.数据将仅在请求范围内，并在处理请求后被垃圾回收.

If what bothers you is to use the request to store data when forwarding from the servlet to the JSP, then that shouldn't bother you: it's the only clean way to do it. The data will be scoped to the request only, and be garbage-collected when the request has been processed.

这篇关于将数据传递到表单时的Post-Redirect-Get?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！