JSP 2.0 Tag Files - is it possible to pass dynamic-attributes from one to another?

[Matt Raible]

I'm using JSP 2.0 Tag files in a Struts 2 application. If I do something like the following, it works great:

<tag:anogb href="@vs@STATIC + '?key=about_invitations'" style="color: red">invited</tag:anogb>

In anogb.tag, I have:

<%@ tag body-content="scriptless" dynamic-attributes="dynattrs" %>
<%@ include file="/WEB-INF/tags/taglibs.jspf"%>
<%@ attribute name="href" required="true" %>
<a href="${url}" <c:forEach items="${dynattrs}" var="a"> ${a.key}="${a.value}"</c:forEach>><jsp:doBody/></a>

However, if I change anogb.tag to reference another tag file, I'm unable to pass the dynamic-attributes to it. I've tried just about everything but haven't found a solution yet. Any ideas?

Thanks,

Matt

[Christophe Verré]

if I change anogb.tag to reference another tag file

What do you mean by that ?

[Stefan Evans]

The dynamic attributes are stored in a Map.
The Map is accessible in pageContext under the attribute with the name specified by the attribute "dynamic-attributes"

So within your tag file because you had <%@ dynamic-attributes="dynattrs" %>, you can reference ${dynattrs} to get the map of dynamic attributes.

You would have to pass it directly to any other tags that you want to use it. It would pass as a Map. I don't see any issues doing that, what problem are you having?

[Matt Raible]

Here's my JSP that's calling my tag file:

<li:anogb href="@vs@STATIC + '?key=about_invitations'" style="color: red">invited</li:anogb>

In anogb.tag, I have:

<%@ tag body-content="scriptless" dynamic-attributes="dynattrs" %>
<%@ taglib uri="/struts-tags" prefix="s" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%@ attribute name="href" required="true" %>
<%@ taglib prefix="li" tagdir="/WEB-INF/tags" %>
 
<s:set name="processedURL" value="${href}"/>
<li:a href="${processedURL}"><jsp:doBody/></li:a>

How do I pass {dynattrs} to my a.tag file in order to render the "style" attribute?

In a.tag, I have:

<%@ tag body-content="scriptless" dynamic-attributes="dynattrs" %>
<%@ taglib uri="/struts-tags" prefix="s" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%@ attribute name="href" required="true" %>
 
<s:set name="url" value="adjustURL('${href}', @com.company.webapp.URLOrigin@A_HREF)"/>
<a href="${url}" <c:forEach items="${dynattrs}" var="a"> ${a.key}="${a.value}"</c:forEach>><jsp:doBody/></a>

If I call <li:a> directly from my JSP, it works fine and renders the style attribute. However, if I try to pass the attributes to <li:a> with the following code, it bombs:

<li:a href="${processedURL}" <c:forEach items="${dynattrs}" var="a"> ${a.key}="${a.value}"</c:forEach>><jsp:doBody/></li:a>

Error reported:

org.apache.jasper.JasperException: /WEB-INF/tags/anogb.tag(10,29) Unterminated <li:a tag
        at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
        at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:376)

Thanks,

[Stefan Evans]

Ok.
You can't nest custom tags in this manner.
You can't use a custom tag as an attribute to another custom tag.

Dynamic attributes are meant so that the tag will handle whatever parameters you pass it at runtime. However you can't dynamically create the attributes to the tag and then evaluate the tag in this manner.

An alternative would be to define another attribute to the <li:a> tag which takes a Map of name/value pairs.

ie like this

<li:a href="${processedURL}" extraAttributes="${dynattrs}">
  <jsp:doBody/>
</li:a>

[Matt Raible]

Originally posted by Stefan Evans:
Ok.
You can't nest custom tags in this manner.
You can't use a custom tag as an attribute to another custom tag.

Dynamic attributes are meant so that the tag will handle whatever parameters you pass it at runtime. However you can't dynamically create the attributes to the tag and then evaluate the tag in this manner.

An alternative would be to define another attribute to the <li:a> tag which takes a Map of name/value pairs.

ie like this

<li:a href="${processedURL}" extraAttributes="${dynattrs}">
  <jsp:doBody/>
</li:a>

That's what I figured when I first started trying to solve this. However, your suggestion doesn't seem to work. In my "a.tag" file, I have:

<%@ attribute name="extraAttributes" required="false" %>
...
<a href="${url}" <c:forEach items="${extraAttributes}" var="a"> ${a.key}="${a.value}"</c:forEach>><jsp:doBody/></a>

And this results in:

java.lang.ExceptionInInitializerError
        at org.apache.commons.el.ArraySuffix.evaluate(ArraySuffix.java:286)
        at org.apache.commons.el.ComplexValue.evaluate(ComplexValue.java:106)
        at org.apache.commons.el.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:211)
        at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:899)
        at org.apache.jsp.tag.web.a_tag._jspx_meth_c_forEach_0(a_tag.java:164)
        at org.apache.jsp.tag.web.a_tag.doTag(a_tag.java:94)
        at org.apache.jsp.tag.web.anogb_tag._jspx_meth_li_a_0(anogb_tag.java:142)
        at org.apache.jsp.tag.web.anogb_tag.doTag(anogb_tag.java:83)

[Stefan Evans]

<%@ attribute name="extraAttributes" required="false" type="java.util.Map" %>

Is there a "caused by" section in that stack trace that you have chopped off?

[Matt Raible]

Adding type="java.util.Map" worked. Thanks! Unfortunately, I don't see a "caused by" in my stack trace.

I do see a NoClassDefFoundError though:

java.lang.NoClassDefFoundError
        at org.apache.commons.el.ArraySuffix.evaluate(ArraySuffix.java:286)
        at org.apache.commons.el.ComplexValue.evaluate(ComplexValue.java:106)
        at org.apache.commons.el.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:211)
        at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:899)
        at org.apache.jsp.tag.web.a_tag._jspx_meth_c_forEach_0(a_tag.java:170)
        at org.apache.jsp.tag.web.a_tag.doTag(a_tag.java:100)
        at org.apache.jsp.tag.web.anogb_tag._jspx_meth_li_a_0(anogb_tag.java:142)
        at org.apache.jsp.tag.web.anogb_tag.doTag(anogb_tag.java:83)