如何从 HttpServletRequest 对象访问 Struts 值堆栈？

发布于 2024-11-28 05:20:52 字数 694 浏览 0 评论 0原文

我遇到过一些代码，通过简单地调用 HttpServletRequest 对象上的 getAttribute() 来访问存储在 struts 值堆栈中的值。我认为这是不可能的，它记录在哪里？

来自操作类的代码（它不会将其添加到类中，仅添加到值堆栈中）：

private PaginatedChunk searchResults;   


public PaginatedChunk getSearchResults() {
    return searchResults;
}

public void setSearchResults(PaginatedChunk searchResults) {
    this.searchResults = searchResults;
}

这是自定义标记中的代码，用于从请求中提取值（并且它有效！？）：

HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
PaginatedChunk searchResults = (PaginatedChunk)  request.getAttribute("searchResults");

有人可以向我解释一下这是如何实现的吗？作品？我认为值堆栈无法通过请求直接访问。

我们运行的是struts2 v2.1.8.1

原文

I have come across some code that is accessing a value that is stored in the struts value stack by simply calling getAttribute() on the HttpServletRequest object. I didnt think this was possible and where is it documented?

Code from the action class (it does not add it to class only to the value stack):

private PaginatedChunk searchResults;   


public PaginatedChunk getSearchResults() {
    return searchResults;
}

public void setSearchResults(PaginatedChunk searchResults) {
    this.searchResults = searchResults;
}

This is the code in a custom tag that pulls the value from the request (and it works!?):

HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
PaginatedChunk searchResults = (PaginatedChunk)  request.getAttribute("searchResults");

Can someone explain to me how this works? I thought the value Stack wasn't directly accessible through the request.

We are running struts2 v2.1.8.1

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鹿港巷口少年归 2024-12-05 05:20:52

乍一看我肯定同意。你所展示的内容看起来并不直观。但真正发生的是从值堆栈访问请求对象，而不是反之亦然。您从值堆栈中的 pageContext 开始，并且您仍在最后处理仍然可以访问值堆栈的内容（它也可以访问请求）。这是它是如何发生的：

看这里（ http:// www.docjar.com/html/api/org/apache/struts2/ServletActionContext.java.html ）我们看到“pageContext”来自哪里：

   93       public static PageContext getPageContext() {
   94           return (PageContext) ActionContext.getContext().get(PAGE_CONTEXT);
   95       }

getContext().get() 返回一个对象，我们知道它是一种PageContext 的。但什么是实现类呢？

创建一个简单的操作：

package com.quaternion.action.test;

import com.opensymphony.xwork2.ActionSupport;

public class RequestAccessTest extends ActionSupport{
    public String getGreeting(){
        return "Hello from Request AccessTest";
    }
}

然后在 JSP 中：

<%@taglib prefix="s" uri="/struts-tags"%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <body>
        <h1>Request Access Test</h1>
        <%
            HttpServletRequest r = (HttpServletRequest) pageContext.getRequest();
            String aGreeting = (String) r.getAttribute("greeting");
            System.out.println(aGreeting);
            System.out.println("R's class is:" + r.getClass().getCanonicalName());
        %>
    </body>
</html>

在我的控制台上，我看到打印：

INFO: Hello from Request AccessTest
INFO: R's class is:org.apache.struts2.dispatcher.StrutsRequestWrapper

所以我们实际上正在处理 StrutsRequestWrapper （现在我们知道我们实际上在处理什么，这很容易）...

http://massapi.com/source/struts-2.2.1/src/core/src/main/java/org/apache/struts2/dispatcher/StrutsRequestWrapper.java.html

寻找在上面的链接中我们看到 getAttribute 确实被重写了。

从第 65 行开始，我们看到它尝试从请求中获取值，如果失败，它会继续从值堆栈中获取值。

这是在哪里记录的？我想到目前为止，它已记录在这里；）

At first glance I would definitely agree. What you show does not look intuitive. But what is really happening is gaining access to the request object from the value stack, not really vice versa. You start with pageContext in the value stack, and you are still working with something at the end which still has access to the value stack (it also has access to the request too). Here is how it happens:

Looking here ( http://www.docjar.com/html/api/org/apache/struts2/ServletActionContext.java.html ) we see where "pageContext" comes from:

   93       public static PageContext getPageContext() {
   94           return (PageContext) ActionContext.getContext().get(PAGE_CONTEXT);
   95       }

getContext().get() returns an Object, which we know is a kind of PageContext. But what is the implementing class?

Creating a simple action:

package com.quaternion.action.test;

import com.opensymphony.xwork2.ActionSupport;

public class RequestAccessTest extends ActionSupport{
    public String getGreeting(){
        return "Hello from Request AccessTest";
    }
}

Then in the JSP:

<%@taglib prefix="s" uri="/struts-tags"%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <body>
        <h1>Request Access Test</h1>
        <%
            HttpServletRequest r = (HttpServletRequest) pageContext.getRequest();
            String aGreeting = (String) r.getAttribute("greeting");
            System.out.println(aGreeting);
            System.out.println("R's class is:" + r.getClass().getCanonicalName());
        %>
    </body>
</html>

On my console I see printed:

INFO: Hello from Request AccessTest
INFO: R's class is:org.apache.struts2.dispatcher.StrutsRequestWrapper

So we are really dealing with a StrutsRequestWrapper (Now that we know what we're actually dealing with it's easy)...

http://massapi.com/source/struts-2.2.1/src/core/src/main/java/org/apache/struts2/dispatcher/StrutsRequestWrapper.java.html

Looking at the above link We see that getAttribute is indeed overridden.

Starting at line 65, we see it tried to get the value out of the request, and then if that fails it goes on to get it out of the value stack.

Where is this documented? I guess it's documented here, as of now ;)

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