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From "Manuel Tromm" <tr...@oTRIs.de>
Subject Re: XTags: Usage of org.dom4j.Documents?
Date Mon, 10 Sep 2001 13:29:06 GMT
Hi James,

thank you again for your help on my XTags-question.
I hope you enjoyed your vacation.  ;-)

I've tried it out with the latest XTags build and
dom4j-1.0 under Tomcat 3.2.2.

Using the <xtags:parse id="myDoc"> in combination with
the <xtags:forEach context="<%= myDoc %>"> works fine,
but passing in an org.dom4j.Document via the context
attribute will lead the "forEach"-XTag to an exception.
The exception always occurrs *after the last* iteration.
What can I do? Have I done something wrong or is it a bug?

I've attached a test JSP-File to this mail for you.


Regards,
Manuel



<h1>Error: 500</h1>
<h2>Location: /jsp/test_for_each_context.jsp</h2><b>Internal Servlet
Error:</b><br><pre>javax.servlet.ServletException
	at
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImp
l.java:459)
	at
jsp._0002fjsp_0002ftest_0005ffor_0005feach_0005fcontext_0002ejsptest_0005ffo
r_0005feach_0005fcontext_jsp_0._jspService(_0002fjsp_0002ftest_0005ffor_0005
feach_0005fcontext_0002ejsptest_0005ffor_0005feach_0005fcontext_jsp_0.java:1
34)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at
org.apache.jasper.servlet.JspServlet$JspCountedServlet.service(JspServlet.ja
va:130)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at
org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.ja
va:282)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:429)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:500)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:405)
	at org.apache.tomcat.core.Handler.service(Handler.java:287)
	at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
	at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:79
7)
	at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
	at
org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpC
onnectionHandler.java:213)
	at
org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
	at
org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:501)
	at java.lang.Thread.run(Thread.java:484)
</pre>
<b>Root cause:</b>
<pre>java.lang.NullPointerException
	at java.util.Hashtable.put(Hashtable.java:380)
	at
org.apache.jasper.runtime.PageContextImpl.setAttribute(PageContextImpl.java:
258)
	at
org.apache.taglibs.xtags.xpath.TagHelper.setInputNodes(TagHelper.java:160)
	at
org.apache.taglibs.xtags.xpath.ForEachTag.doAfterBody(ForEachTag.java:154)
	at
jsp._0002fjsp_0002ftest_0005ffor_0005feach_0005fcontext_0002ejsptest_0005ffo
r_0005feach_0005fcontext_jsp_0._jspService(_0002fjsp_0002ftest_0005ffor_0005
feach_0005fcontext_0002ejsptest_0005ffor_0005feach_0005fcontext_jsp_0.java:1
15)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at
org.apache.jasper.servlet.JspServlet$JspCountedServlet.service(JspServlet.ja
va:130)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at
org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.ja
va:282)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:429)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:500)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:405)
	at org.apache.tomcat.core.Handler.service(Handler.java:287)
	at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
	at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:79
7)
	at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
	at
org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpC
onnectionHandler.java:213)
	at
org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
	at
org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:501)
	at java.lang.Thread.run(Thread.java:484)
</pre>



-----Urspr√ľngliche Nachricht-----
Von: James Strachan [mailto:james_strachan@yahoo.co.uk]
Gesendet: Sonntag, 9. September 2001 21:21
An: taglibs-user@jakarta.apache.org
Betreff: Re: XTags: Usage of org.dom4j.Documents?


Hi Manuel

Sorry for the delay getting back to you, I'm just back from vacation.

The quick answer is absolutely yes - you can pass in documents, nodes or
'node sets' (a List of Node objects) to all the tags. This is achieved via
either the context attribute using a scriptlet expression or via XPath
variables.

e.g.

<xtags:forEach select="foo/bar" context="<%= mydoc %>">
    ...
</xtags:forEach>

You can define a variable for any expression or parse to allow you to
evaluate once and keep it around for future reference.

e.g.

<xtags:parse id="mydoc">
    <some>
        <tag>hello there</tag>
    </some>
</xtags:parse>

then later...

<xtags:valueOf select="/some/tag" context="<%= mydoc %>"/>

or you could use the XPath variables. Whenever an attribute is defined in
page / request / session / application scope it is available as an XPath
variable. So you could rewrite the above as

<xtags:valueOf select="$mydoc/some/tag"/>

You can also use the <xtags:variable> tag to define a variable of an XPath
expression, to avoid reevaluation. e.g.

<xtags:variable id="mytags" select="//tag"/>

Of course you could always define your own scripting variables for documents
and pass them in as a context parameter or create your own attributes and
use the XPath variable syntax.

Hope that helps.

James
----- Original Message -----
From: "Manuel Tromm" <tromm@oTRIs.de>
To: <taglibs-user@jakarta.apache.org>
Sent: Thursday, September 06, 2001 9:36 AM
Subject: XTags: Usage of org.dom4j.Documents?


> Hi folks,
>
> I've got a question about using XTags:
>
> The common way to use the XTags, is to parse an XML document
> from somewhere by using the "<xtags:parse>"-Tag.
> After the XML-Code has been parsed, it can be accessed
> by the different "X"-Tags...
>
> Sometimes I have to use the XML-Source
> (that is needed as input for XTags) twice or more or
> at completely different locations of my web-application.
> For this reason I've added the XML-Code to a cache.
> The problem is now, that every time when the XTags-JSP is
> requested, the XML-Input has to be parsed by the XTags again.
> That means a lack of performance.
>
> Now my question: Because the XTags are built on top
> of the dom4j, I'd like to know if there is any way to use
> an (already parsed!) org.dom4j.Document as input for
> XTags, so that I don't have to parse XML-Sources twice?
> If yet there is no way, I'd like to ask the developers
> to provide an appropriate Tag, because I think it would be
> also quite helpful for other users.
>
> Does someone know a solution?
>
>
> Regards,
> Manuel Tromm
>

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