在同一个jsp上从javascript访问java变量 [英] Accessing java variable from javascript on same jsp
问题描述
是否可以从同一页面上的javascript访问jsp中定义的String类型变量？
Is it possible to access a String type variable defined in jsp from a javascript on the same page?
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1255">
<title>Insert title here</title>
<script type="text/javascript">
foo();
function foo()
{
var value = "<%=myVar%>";
alert(value);
}
</script>
</head>
<body>
<%
String myVar="blabla";
%>
</body>
</html>
在eclipse中我收到错误
In eclipse I am getting an error
myVar cannot be resolved to a variable
推荐答案
由于您尝试使用未定义的变量，因此无效。代码生成如下：
This won't work since you're trying to use an undefined variable. The code is generated like this:
... = myVar;
//...
String myVar = "blabla";
没有意义，对吧？因此，为了使这项工作你应该在使用之前声明变量（一如既往）：
Doesn't make sense, right? So, in order to make this work you should declare the variable before using it (as always):
<%
String myVar="blabla";
%>
<script type="text/javascript">
foo();
function foo() {
var value = "<%=myVar%>";
alert(value);
}
</script>
仍然，使用scriptlet 非常气馁。假设您正在使用 JSTL 和表达语言（EL），这可以改写为：
Still, usage of scriptlets is extremely discouraged. Assuming you're using JSTL and Expression Language (EL), this can be rewritten to:
<c:set name="myVar" value="blabla" />
<script type="text/javascript">
foo();
function foo() {
var value = "${myVar}";
alert(value);
}
</script>
如果您的变量中包含等字符那么这种方法就会失败。你可以通过JSTL使用< c：out> 来逃避结果：
If your variable has characters like " inside, then this approach will faile. You can escape the result by using <c:out> from JSTL:
var value = "<c:out value='${myVar}' />";
更多信息：
- How to avoid Java code in JSP files?
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