How can I pass a server side variable into a core tag in JSP?

问题

This expression tag outpus a correct value for me <%=drug.NonAuthoritative%>

while I cant recover the value of drug.NonAuthoritative for use in a C tag

<c:if test="${drug.NonAuthoritative}">&nbsp;<bean:message key="WriteScript.msgNonAuthoritative"></bean:message></c:if>

the method is

public Boolean NonAuthoritative() {
    return nonAuthoritative;
}

回答1:

There are 2 problems:

Scriptlets and EL do not share the same scope. The drug in ${drug} has to match the name of an existing attribute in the page, request, session or application scope. If you're preparing drug in a scriptlet instead of in a controller, then you should put it as an attribute in one of those scopes yourself.
```
<% 
    Drug drug = new Drug();
    // ...
    request.setAttribute("drug", drug);
%>
```
(as partly answered by Nathan), EL relies on Javabeans specification. The ${drug.propertyName} requires a public method getPropertyName() for non-boolean properties or isPropertyName() for boolean properties. So, this should do
```
public class Drug {

    private boolean nonAuthorative;

    public boolean isNonAuthorative() {
        return nonAuthorative;
    }

    // ...
}
```
with
```
<c:if test="${drug.nonAuthoritative}">
```
(pay attention to the casing!)

回答2:

The scriptlet <%=drug.NonAuthoritative%> uses the field NonAuthoritative of the drug instance.

The EL expression ${drug.NonAuthoritative} uses the method isNonAuthoritative() of the drug instance.

To make this work, keep the EL expression as-is, but add this method to your drug class:

public boolean isNonAuthoritative() {
  return NonAuthoritative;
}

回答3:

That's because the JSTL is assuming you're using JavaBean standards, so when you call something drug.NonAuthoritative in a JSTL expression it's looking for a method called getNonAuthoritative() (or alternatively isNonAuthoritative()). The scriptlet doesn't make that assumption, it just evaluates what you give it.

来源：https://stackoverflow.com/questions/5859023/how-can-i-pass-a-server-side-variable-into-a-core-tag-in-jsp

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jsp-tags