HttpSession setAttribute并不总是插入新对象 [英] HttpSession setAttribute doesn't always insert new object
问题描述
我正在从WLS10g和JavaEE6升级到WLS12c和JavaEE7。
I am working on an upgrade from WLS10g and JavaEE6 to WLS12c and JavaEE7.
我注意到 HttpSession.setAttribute <的差异/ code>有效。在WLS10中，任何已存储在某个键下的对象都将被替换。
I have noticed a difference on how HttpSession.setAttribute works. In WLS10, any object already stored under a certain key would always be replaced.
在WLS12中，如果 newObject.equals（oldObject），则不会替换该对象。
In WLS12 the object is not replaced if newObject.equals(oldObject).
这对我们来说是一个问题，因为应用程序有这样的对象：
This is a problem for us, because the applications have objects like this:
class ValueObject {
int key;
String data;
@Override
public int hashCode()
{
return key;
}
boolean equals(Object o) {
if (o == null || (o instanceof ValueObject) == false) {
return false;
}
ValueObject otherObject = (ValueObject)o;
/* Return true if the keys are equal, even though the data may differ */
return key == otherObject.key;
}
}
ValueObject通过跨越多个web的工作流程进行修改页面。中间值存储在 HTTPSession 中，在工作流结束时，修改后的值将写入数据库。
The ValueObject gets modified through a workflow that spans several web pages. The intermediate values are stored in the HTTPSession and at the end of the workflow the modified value is written to the database.
在servlet中有这样的代码（成员实际上是通过getter / setter修改的，但我正在简化以减少问题中的代码量）：
In the servlets there is code like this (the members are actually modified through getters/setters, but I am simplifying to reduce the amount of code in the question):
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException {
HttpSession session = request.getSession();
ValueObject newValue = new ValueObject();
newValue.key = Integer.parseInt(request.getParameter("key"));
newValue.data = request.getParameter("data");
session.setAttribute("value", newValue);
...
newValue.key 未修改，而 newValue.data 有一个新值。
newValue.key is unmodified while newValue.data has a new value.
<$ c $的修改行为WLS12中的HttpSession 打破了这种模式 - 当从会话中检索到对象时，我们从第一步开始获得数据，因为对象是'n'当我们尝试存储更新版本时，t会被替换。
The modified behaviour of the HttpSession in WLS12 breaks this pattern - when the object is retrieved from the session we get the data from the first step since the object isn't replaced when we try to store updated versions.
我们可以通过更改所有更新来解决此问题：
We could solve this by changing all updates from:
session.setAttribute("value", newValue);
到
session.removeAttribute("value");
session.setAttribute("value", newValue);
但是，有超过100个servlet因此需要做很多工作。解决方法既丑陋又容易出错，因为程序员在编写代码时需要再跟踪一件事。
However, there are more than 100 servlets so it is a lot of work. And the workaround is both ugly and prone to errors because the programmers need to keep track of one more thing when writing code.
有没有办法配置WLS12c来使用对象总是被替换的旧行为HttpSession.setAttribute（）？
Is there any way to configure WLS12c to use the old behaviour where the object always is replaced by HttpSession.setAttribute()?
更新2015-09 -30 ：
向Oracle提交的错误报告。我尝试过wero建议的过滤器想法。似乎Weblogic期望从过滤器链下来的对象是类 weblogic.server.internal.ServletRequestImpl ，因为当我包装它并将包装器发送到过滤器链时我从内部Weblogic类获得了ClassCastException。
Bug report filed with Oracle. I've tried the filter idea suggested by wero. It seems Weblogic expects the object coming down the filter chain to be of class weblogic.server.internal.ServletRequestImpl, because when I wrapped it and sent the wrapper down the filter chain I got a ClassCastException from an internal Weblogic class.
我还检查了Gimby建议的配置选项。我找不到会议的任何适用选项。我们部署到单个服务器并使用 memory 作为会话持久性设置。
I have also checked the configuration options as suggested by Gimby. I could not find any applicable option for the Session. We deploy to a single server and use memory as session persistence setting.
更新2016-02-03 ：
Oracle已关闭错误报告作为不是错误。
Oracle has closed the bug report as "Not a bug".
推荐答案
由于Oracle将错误报告关闭为不是错误，我决定实施变通办法。
Since Oracle closed the bug report as "not a bug" I decided to implement the workaround.
我经历了对 HttpSession.setAttribute 的所有调用，并确定哪些调用使用了可能触发的对象错误。
I went through all calls to HttpSession.setAttribute and identified which calls used an object that potentially could trigger the bug.
在我替换的那些地方
session.setAttribute(key, newValue);
with
session.removeAttribute(key);
session.setAttribute(key, newValue);
以及解释为何需要额外行的评论。
along with a comment explaining why the extra line was needed.
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