Question

Trouble with simple custom tag

Asked by: andrew200

I am trying to run a sample custom tag java application.  I get this error:

org.apache.jasper.JasperException: /index.jsp(23,4) Unable to load tag handler class "java.TestTagClass" for tag "tt:TestTag"

I have double and triple checked all of the paths and directory structure but the error remains the same.

Here is what I have:

The directory structure starts with the root at: c:\Java Projects\WebStuff\WebApplication3

I think these are the important files:

build\web\index.jsp
build\web\WEB-INF\classes\java\TagTest.class
build\web\WEB-INF\lib\jstl.jar
build\web\WEB-INF\lib\standard.jar
build\web\WEB-INF\tlds\TLDTest.tld
build\web\WEB-INF\web.xml

here are some code snippets:

index.jsp:

<%@ taglib uri="TheTag" prefix="tt"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
    <h1>JSP Page</h1>

    <tt:TestTag/>

    </body>
</html>
______________________________________________

web.xml:
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
       version="2.4">
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
      <welcome-file>
            index.jsp
        </welcome-file>
    </welcome-file-list>
<taglib>
    <taglib-uri>TheTag</taglib-uri>
    <taglib-location>/WEB-INF/tlds/TLDTest.tld</taglib-location>
</taglib>
</web-app>

_______________________________________________

TLDTest.tld:

<taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd">
  <tlib-version>1.0</tlib-version>
  <short-name>tt</short-name>
  <uri>/WEB-INF/tlds/TDLTest</uri>
  <tag>
      <name>TestTag</name>
      <tagclass>java.TestTagClass</tagclass>
  </tag>
</taglib>

_______________________________________________

I suspect that for some reason the java.TestTagClass in not being found because I can change the <tagclass> value to anything and I get the same error.

I really want to get this thing to work so I can move on-- your help is appreciated!

Thanks

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Asked On
2007-01-02 at 06:06:00ID22108139
Tags

tag

,

load

,

handler

Topics

Java Programming Language

,

Java Standard Tag Library (JSTL) & Server Tags

,

Extensible HTML (XHTML)

Participating Experts
4
Points
500
Comments
13

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Answers

 

by: pkwanPosted on 2007-01-02 at 07:10:36ID: 18228024

I guess you are typing java.TestTagClass wrongly. Since your class should be: java.TagTest

 

by: dbkrugerPosted on 2007-01-02 at 07:37:17ID: 18228266

You should not be using the package java at all.

Your code should look like

package com.yourcompany;

public class TestTagClass extends ..


And you need to specify the package of your code in the taglib

 

by: andrew200Posted on 2007-01-02 at 08:39:57ID: 18228763

Thank you both for your replies.

pkwan-- You are right.  I copied and pasted incorrectly, the code does not work with java.TagTest either.  Sorry about that.

dbkruger-- What difference does it make if I use com or java for the package?  I created a package called "java" and put the class in there.  How do specify the name of the package in the taglib?

Thanks.

 

by: owenli27Posted on 2007-01-02 at 13:01:59ID: 18230923

Is <tagclass> same as <tag-class> for its usage under <tag> in your TLDTest.tld file?
I always think that we should use <tag-class>, <body-content>...

 

by: rrz@871311Posted on 2007-01-02 at 18:00:44ID: 18232739

owenli is right. That name was changed.  See table 10.1 at  
http://www.phptr.com/articles/article.asp?p=26118&seqNum=6&rl=1  

 

by: andrew200Posted on 2007-01-03 at 04:21:54ID: 18234470

Thank you for your comments.  The link above has some useful information in it.  I made the changes the tags to use the current tag names but I still get the same error:

Unable to load tag handler class "java.TestTag" for tag "tt:TestTag"

It's as though it can't find java.TestTag.  If I change the value of <tag-class> in the TLDTest.tld file to "java.some_random_value" I get the same error:

Unable to load tag handler class "java.some_random_value" for tag "tt:TestTag"

Don't know what's going on.

 

by: owenli27Posted on 2007-01-03 at 06:42:22ID: 18235328

>>Unable to load tag handler class "java.TestTag" for tag "tt:TestTag"

- in your initial posting, your file path ans name should be "build\web\WEB-INF\classes\java\TagTest.class".  So. you TLD file should be <tag-class>java.TagTest</tag-class> instead of ""java.TestTag"

- use directly point to your TLD file in index.jsp taglib directive instead of indirect uri pointing to reduce possible errors. Change this line: <%@ taglib uri="TheTag" prefix="tt"%>
to:  <%@ taglib uri="/WEB-INF/tlds/TDLTest.tld" prefix="tt"%>    
Good Luck






 

by: rrz@871311Posted on 2007-01-03 at 08:09:18ID: 18236230

I agree with dbkruger.  You should not use  java as a package name.

 

by: owenli27Posted on 2007-01-03 at 09:27:09ID: 18236999

After a simple test to use "java" as package name to create a class, I got SecurityException - java.lang.SecurityException: Prohibited package name: java

 

by: andrew200Posted on 2007-01-03 at 09:33:08ID: 18237058

owenli27-- thanks for your suggestion.  I made the change but the error remains.  That was an error that I brought on through my testing.  The problem is still there though.

rrz@971311-- I'll try a different package name.

 

by: andrew200Posted on 2007-01-03 at 10:14:32ID: 18237414

That was it.  I should have tried dbkruger's suggestion from the start.  I don't understand why it would care what name is used in a package, but it does.

Thanks to all.  You can all feel good about the work we have accomplished here-- now go relax.

 

by: rrz@871311Posted on 2007-01-03 at 10:40:19ID: 18237643

>now go relax.
Not while there is so much more to learn !
>I don't understand why it would care what name is used in a package, but it does.
Please read  
http://tomcat.apache.org/tomcat-5.5-doc/class-loader-howto.html  
It would seem that Tomcat will always see the official java package before it sees the one you have created.

 

by: dbkrugerPosted on 2007-01-04 at 10:23:59ID: 18245175

It's not a good idea to change something in the java package under any circumstances, but in this case there are security issues.
Imagine you're a web server, being told to access code in the standard package, but to replace it by user code. In your case of course, you were writing a new class, but they don't know that. Imagine you re-wrote System.OutputStream. Should everyone else have to run your version? There are many much more subtle issues, but the bottom line is that you don't own the java package, the language does. Unless you are re-implementing a feature from Sun, you should stay in your own namespace.

Glad to be of help!

cheers,
Dov

20120131-EE-VQP-002

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