问题描述
作为这个问题的扩展，我正在尝试将 Javascript 插入 <h:commandButton/> 的 onclick 属性，因为 action 已经在呈现一个 ajax 表.
As an extension of this question, I'm trying to insert Javascript to a <h:commandButton />'s onclick property as action is already rendering an ajax table.
我想做什么:获取列表框中选定的项目并将它们转换为要在 JSF FileServlet 中使用的参数.即 para2=value1¶m=value2¶m=value3
What I want to do:Get the selected items in a list box and turn them into parameters to be used in a JSF FileServlet. i.e. para2=value1¶m=value2¶m=value3
这是我所拥有的:
<script type ="text/javascript">
function myScript() {
var box = document.getElementbyId('myForm:box');
var length = box.options.length;
var paramstring = "";
for (var i = 0; i < length; i++) {
if (i != (length - 1) {
if (box.options[i].selected) {
paramstring = paramstring + "param=" + box.options[i].value + "&";
}
} else {
paramstring = paramstring + "param=" + box.options[i].value;
}
}
if (document.getElementById('myForm:checkbox').checked) {
window.location='fileServlet? + paramstring;
}
}
</script>
页面加载时我得到了什么:javax.servlet.ServletException: Error Parsing/page.xhtml: Error Traced[line:15] 元素的内容必须由格式正确的字符数据或标记组成.
What I get when page is loaded:javax.servlet.ServletException: Error Parsing /page.xhtml: Error Traced[line:15] The content of elements must consist of well-formed character data or markup.
什么不会触发异常:
<script type ="text/javascript">
function myScript() {
var box = document.getElementbyId('myForm:box');
var length = box.options.length;
var paramstring = "";
if (document.getElementById('myForm:checkbox').checked) {
window.location='fileServlet? + paramstring;
}
}
</script>
只要我添加 for (var i = 0; i 甚至 for (var i = 0; i 页面无法加载.为什么它不喜欢 for 循环?
As soon as I add in for (var i = 0; i < length; i++) or even for (var i = 0; i < 10; i++) the page wouldn't load. Why does it not like the for loop?
推荐答案
Facelets 是一种基于 XML 的视图技术，它使用 XHTML+XML 生成 HTML 输出.XML 有五个特殊字符，它们被 XML 解析器特殊处理:
Facelets is a XML based view technology which uses XHTML+XML to generate HTML output. XML has five special characters which has special treatment by the XML parser:
<标签的开始.>标签的结尾."属性值的开始和结束.'属性值的替代开始和结束.&实体的开始(以;结尾).
<the start of a tag.>the end of a tag."the start and end of an attribute value.'the alternative start and end of an attribute value.&the start of an entity (which ends with;).
在 < 的情况下，XML 解析器隐式地寻找标签名称和结束标签 >.但是，在您的特定情况下，您使用 < 作为 JavaScript 运算符，而不是作为 XML 实体.这完全解释了您遇到的 XML 解析错误:
In case of <, the XML parser is implicitly looking for the tag name and the end tag >. However, in your particular case, you were using < as a JavaScript operator, not as an XML entity. This totally explains the XML parsing error you got:
元素的内容必须由格式良好的字符数据或标记组成.
本质上，您在错误的地方编写了 JavaScript 代码，即 XML 文档而不是 JS 文件，因此您应该相应地转义所有 XML 特殊字符.< 必须转义为 <.
In essence, you're writing JavaScript code in the wrong place, a XML document instead of a JS file, so you should be escaping all XML special characters accordingly. The < must be escaped as <.
所以，本质上，
for (var i = 0; i < length; i++) {
必须成为
for (var i = 0; i < length; i++) {
使其对 XML 有效.
to make it XML-valid.
然而，这使得 JavaScript 代码更难阅读和维护.正如 Mozilla 开发者网络的优秀文档 Writing JavaScript for XHTML 所述，您应该将 JavaScript 代码放在字符数据 (CDATA) 块中.因此，在 JSF 术语中，这将是:
However, this makes the JavaScript code harder to read and maintain. As stated in Mozilla Developer Network's excellent document Writing JavaScript for XHTML, you should be placing the JavaScript code in a character data (CDATA) block. Thus, in JSF terms, that would be:
<h:outputScript>
<![CDATA[
// ...
]]>
</h:outputScript>
XML 解析器会将块的内容解释为普通的"；字符数据而不是 XML，因此将 XML 特殊字符按原样"解释.
The XML parser will interpret the block's contents as "plain vanilla" character data and not as XML and hence interpret the XML special characters "as-is".
但是，更好的是将 JS 代码放在它自己的 JS 文件中，该文件由 <script src> 包含，或者在 JSF 术语中，<h:outputScript>.
But, much better is to just put the JS code in its own JS file which you include by <script src>, or in JSF terms, the <h:outputScript>.
<h:outputScript name="functions.js" target="head" />
这样您就无需担心 JS 代码中的 XML 特殊字符.另一个好处是，这让浏览器有机会缓存 JS 文件，从而使平均响应大小更小.
This way you don't need to worry about XML-special characters in your JS code. Additional advantage is that this gives the browser the opportunity to cache the JS file so that average response size is smaller.
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