java 在 JSP 中，path 和 value 属性在 input 标签中做什么，表单前缀如何影响它们？
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In JSP, what do the path and value attribute do within the input tag, and how does the form prefix affect them?
提问by Danny
Just wanted a clear answer for a direct question -- google results have been all over the place or don't address the combos you'll see below.
只是想要一个直接问题的明确答案 - 谷歌搜索结果到处都是，或者没有解决您将在下面看到的组合。
I'm generally a JSP newbie and have been screwing around with the following code.
我通常是一个 JSP 新手，并且一直在使用以下代码。
<form:input id="theId" path="path.copied.directly.fromSomewhereElse"
cssClass="contentTextInput" cssStyle="width: 229px" />
When I put that into my JSP page and load my website, it works fine and looks as my cssClass defines it. Then I start messing with it because I want it to display a default value.
当我将它放入我的 JSP 页面并加载我的网站时，它工作正常并且看起来就像我的 cssClass 定义的那样。然后我开始弄乱它，因为我希望它显示一个默认值。
<form:input id="theId" path="path.copied.directly.fromSomewhereElse"
value="blah" cssClass="contentTextInput" cssStyle="width: 229px" />
Suddenly, HTTP 500, an org.apache.jasper.JasperException! So I decide to remove the pathaltogether, while leaving in the value. This is just step 1 in something I know works because of prior experience. The code is now:
突然，HTTP 500，一个 org.apache.jasper.JasperException！所以我决定完全删除路径，同时保留值。由于先前的经验，这只是我知道可行的事情的第 1 步。现在的代码是：
<form:input id="theId" value="someClass.valueIWantAsDefault"
cssClass="contentTextInput" cssStyle="width: 229px" />
That actually throws an exception, too -- but then I remove the form prefix and it works-- mostly. You see, the cssClass's effects are now gone; it looks like a regular, unaffected input textbox. Here's the code so far.
这实际上也引发了一个异常——但随后我删除了表单前缀并且它起作用了——主要是。你看，cssClass 的效果现在不见了；它看起来像一个普通的、不受影响的输入文本框。这是到目前为止的代码。
<input id="theId" value="someClass.valueIWantAsDefault"
cssClass="contentTextInput" cssStyle="width: 229px" />
What exactly do these attributes (and prefix) do that makes this mix-and-match work?
这些属性（和前缀）究竟做了什么使这种混合匹配起作用？
回答by Asaph
I'm guessing you're dealing with a jsp page that relies on a JSP custom tag library that's part of the Spring Framework. Here are the docs for the <form:input>tag. valueis not a valid attribute for this custom tag as you can see in the docs link I provided above. When you remove the form:, you're turning the tag into a plain old HTML <input>tag which is why your error is going away at that point. It's also why your css stops working. cssClassis not the correct attribute for the HTML <input>tag. It's simply class. They called it cssClassin the jsp custom tag lib most likely to avoid a lower level collision with the Object.getClass()method (long story, just take my word for it).
我猜您正在处理一个依赖 JSP 自定义标记库的 jsp 页面，该库是 Spring 框架的一部分。这是<form:input>标签的文档。value不是此自定义标记的有效属性，如您在我上面提供的文档链接中所见。当您删除 时，您会将form:标签变成一个普通的旧 HTML<input>标签，这就是为什么您的错误在那一点消失的原因。这也是您的 css 停止工作的原因。cssClass不是 HTML<input>标记的正确属性。简直了class。他们cssClass在 jsp 自定义标签库中调用它最有可能避免与该Object.getClass()方法发生较低级别的冲突（长话短说，相信我的话）。
