Taglib problem in JSP

Question

I'm using JFreeChart to display the chart and I define the following taglib in my JSP.
<%@ taglib uri="/WEB-INF/chartlib.tld" prefix="chartlib" %>
It works in Tomcat and WebLogic, but not webtogo, got this exception.
java.lang.NoClassDefFoundError: Illegal name: /WEB-INF/chartlib.tld
     at java.lang.ClassLoader.defineClass(Unknown Source)
     at java.lang.ClassLoader.defineClass(Unknown Source)
     at oracle.lite.web.ServletHandler$ServletClassLoader.loadClass(Unknown Source)
     at java.lang.ClassLoader.loadClass(Unknown Source)
     at oracle.jsp.parse.JspUtils.loadClassJDK(JspUtils.java:219)
     at oracle.jsp.parse.JspUtils.loadClass(JspUtils.java:209)
I have to hardcode the app name in order to make it work. Is there any good solution?
<%@ taglib uri="//webapp/WEB-INF/chartlib.tld" prefix="chartlib" %>
And it just solve the exception problem, it actually cannot show the chart. Anyone use the jfreechart or has problem in using custom tag library?
Matthew

Answer 1

I put the chartlib.tld in /WEB-INF/ and here is my web.xml. The uri of the taglib directive in JSP is exactly the taglib-uri here for each case.
<taglib>
<taglib-uri>/WEB-INF/chartlib.tld</taglib-uri>
<taglib-location>/WEB-INF/chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>chartlib-01.tld</taglib-uri>
<taglib-location>/chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>chartlib-02.tld</taglib-uri>
<taglib-location>/no_chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>chartlib-03.tld</taglib-uri>
<taglib-location>/WEB-INF/chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>chartlib-04.tld</taglib-uri>
<taglib-location>chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>chartlib-05.tld</taglib-uri>
<taglib-location>no_chartlib.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>/WEB/chartlib.tld</taglib-uri>
<taglib-location>/WEB-INF/chartlib.tld</taglib-location>
</taglib>
And I have modified the source code in JspDirectiveTaglib.java to output some debug message, where s1 is the value of uri in JSP, s3 is the value of taglib-location in web.xml. Here is the result. It tries to load s1 first. If it returns null, then it reads the tld file s2. It shows that the leading '/' represent the webapp dir. If it is relative (i.e. no '/'), it refers to the /WEB-INF as you can see the program automatically add it in the beginning. Finally, the message "loader MyChartTag" shows that it loads my tag class successfully.
----Case 1: this should be the normal/ideal case, but in fact it fails.
----It loads the tld file but it is not a class, so throws the error.
JspDirectiveTaglib:uri(s1)=[WEB-INF/chartlib.tld]
JspDirectiveTaglib:s3=[WEB-INF/chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[WEB-INF/chartlib.tld]
log1: loader: /WEB-INF/chartlib.tld
log9: JspServlet: unable to dispatch to requested page: java.lang.NoClassDefFoundError:
Illegal name: /WEB-INF/chartlib.tld
----Case 2: try to read tld in root dir.
JspDirectiveTaglib:uri(s1)=[chartlib-01.tld]
JspDirectiveTaglib:s3=[chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[chartlib-01.tld]
JspDirectiveTaglib:class1=null
log9: JspServlet: unable to dispatch to requested page: oracle.jsp.parse.JspParseException:
Error: java.io.FileNotFoundException:
F:\webapp\chartlib.tld (???????????)
----Case 3: try to read a non-existing tld to see where is the root dir.
JspDirectiveTaglib:uri(s1)=[chartlib-02.tld]
JspDirectiveTaglib:s3=[no_chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[chartlib-02.tld]
JspDirectiveTaglib:class1=null
log9: JspServlet: unable to dispatch to requested page: oracle.jsp.parse.JspParseException:
Error: java.io.FileNotFoundException:
F:\webapp\no_chartlib.tld (???????????)
----Case 4: try to read tld in absolute dir.
JspDirectiveTaglib:uri(s1)=[chartlib-03.tld]
JspDirectiveTaglib:s3=[WEB-INF/chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[chartlib-03.tld]
JspDirectiveTaglib:class1=null
log1: loader: MyChartTag
----Case 5: try to read tld in relative dir, but the path is changed by the program.
JspDirectiveTaglib:uri(s1)=[chartlib-04.tld]
JspDirectiveTaglib:s3=[WEB-INF/chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[chartlib-04.tld]
JspDirectiveTaglib:class1=null
log1: loader: MyChartTag
----Case 6: try to read a non-existing tld in relative dir, but the path is changed by the program.
JspDirectiveTaglib:uri(s1)=[chartlib-05.tld]
JspDirectiveTaglib:s3=[WEB-INF/no_chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[chartlib-05.tld]
JspDirectiveTaglib:class1=null
log9: JspServlet: unable to dispatch to requested page: oracle.jsp.parse.JspParseException:
Error: java.io.FileNotFoundException:
F:\webapp\WEB-INF\no_chartlib.tld (???????????)
----Case 7: try to compare to case 1 if the uri specifies an invalid path.
JspDirectiveTaglib:uri(s1)=[WEB/chartlib.tld]
JspDirectiveTaglib:s3=[WEB-INF/chartlib.tld]
JspDirectiveTaglib:loadClass(s1)=[WEB/chartlib.tld]
JspDirectiveTaglib:class1=null
log1: loader: MyChartTag