spring form taglib disable属性是否真的必须解析为字符串? [英] Does spring form taglib disabled attribute really have to resolve to a string?

问题描述

我最近一直在使用spring形式的taglib，遇到了一个相当令人不安的现象.

I've been playing around with the spring form taglib lately and came across a fairly disturbing phenomenon.

<form:select path="whatever" disabled="${true}">

将呈现未禁用的选择元素

Will render a select element that is NOT disabled

<form:select path="whatever" disabled="${'true'}">

将呈现被禁用的选择元素.

Will render a select element that IS disabled.

这向我表明，标记在该属性中需要一个字符串，并且拒绝强制使用任何布尔值(可能首先检查类型).

This indicates to me that the tag expects a string in that attribute and is refusing to coerce any boolean values (possibly checking the type first).

影响是我无法执行<form:select path="whatever" disabled="${someOtherfield.selectedId != -1}" />之类的事情，而这在我们的系统中经常发生.

The impact is that I'm unable to do something like <form:select path="whatever" disabled="${someOtherfield.selectedId != -1}" /> which is something that happens fairly often in our system.

我只是缺少表单标签库功能的某些部分吗?这是一个合理的设计决定吗?有缺陷吗?

Am I simply missing some part of the form taglibs functionality? Is this a legitimate design decision? A defect?

推荐答案

好吧，我对此做了更多的挖掘，因为这种解决方法看起来太难看了.

Ok, I did some more digging around this one, because the work-arounds were looking too ugly.

http://forum.springsource.org/showthread.php?t=84102

问题是JSP正在评估el，并使用"true"盲目比较评估结果.等于

The problem was that the JSP was evaluating the el, and blindly comparing the result of that evaluation using "true".equals

使用该方法将字符串与布尔值进行比较将始终返回false，因为类型不匹配，因此肯定是缺陷.

Comparing a String to a Boolean using that method will always return false because the type's don't match so it's definitely a defect.

幸运的是，有问题的isDisabled方法是一个受保护的衬套，因此我能够通过扩展8个输入标签的作用并覆盖该方法以进行更稳健的比较来解决该问题.

Fortunately the isDisabled method at fault is a protected one liner, so I have been able to work around it by extending the 8 input tag's effected and overriding that method to do a slightly more robust comparison.

所以答案是，是的，这是一个缺陷，从skaffman的评论看来，随着JSP EL的实现，旧库没有得到很好的更新，这似乎是一个问题.

So the answer is, yes, it is a defect, and from skaffman's comments it looks like it's a bit of a problem with an old library not being very well updated as JSP EL was implemented.

感谢您的回答

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