为什么 ColdFusion SESSION 变量是“未定义的"?在被引用了几行之后? [英] Why is a ColdFusion SESSION variable "undefined" after being referenced a few lines before?

问题描述

在 Windows2003/IIS6 上运行 ColdFusion 8.01 Standard

Running ColdFusion 8.01 Standard on Windows2003/IIS6

Application.cfc:

Application.cfc:

<cfcomponent output="false">
    <cfscript>
        THIS.SessionManagement = "Yes";
        THIS.SessionTimeout = CreateTimeSpan(0, 3, 0, 0);
        THIS.ApplicationTimeout = CreateTimeSpan(0, 8, 0, 0);
    </cfscript>

    <cffunction name="onRequestStart" returnType="Boolean" output="false">
        <cfargument name="targetPage" type="string" required="true">

        <cfscript>
            if  (!StructKeyExists(SESSION, "User"))
                SESSION.User = CreateObject("component", "cfc.User");
        </cfscript>
    </cffunction>
</cfcomponent>

模板文件伪代码示例:

    LOCAL.qItems =
        CreateObject(
                "component",
                "cfc.Items"
                ).setUser(SESSION.User).getItems();

    for (i=1; i<=LOCAL.qItems.RECORDCOUNT; i++) {
        LOCAL.Item =
            CreateObject(
                "component",
                "cfc.Item"
                ).setUser(
                    SESSION.User
                    ).setId(LOCAL.qItems["Sku"][i]);
    }

SESSION.User 在 Application.cfc 的 onRequestStart() 中设置(如果尚未定义).上面的代码在模板文件中运行.对 SESSION.User 的第二次引用引发了异常，并显示消息 Element USER is undefined in SESSION.

SESSION.User is set (if not already defined) in onRequestStart() of Application.cfc. The above code runs in a template file. The second reference to SESSION.User has thrown an exception with the message Element USER is undefined in SESSION.

为什么 SESSION.User 会在几行之前定义(不抛出异常)，然后在几行之后(毫秒内)抛出这个异常?

Why would SESSION.User be defined (doesn't throw an exception) a few lines before, and then throw this exception a few lines later (within milliseconds)?

这可能每天在我的应用程序的不同模板中发生一次.

This happens maybe once a day in different templates throughout my application.

如何防止这种情况发生?

How can I prevent this?

推荐答案

这很可能是线程安全问题，您的代码中的其他内容清除了会话范围或将 NULL 分配给 SESSION.User.

It's most likely a thread safety issue with something else in your code clearing out session scope or assigning NULL to SESSION.User.

我建议您这样做，因为您的循环中似乎没有 i 的本地声明，因此该代码不是线程安全的 - 因此您的代码中的其他地方可能会出现类似的错误.

I suggest that because you don't seem to have a local declaration for i in your loop, so that code is not thread safe - and so you may have similar errors elsewhere in your code.

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