Eclipse "cannot find the tag library descriptor" for custom tags (not JSTL!)

I have a Java EE project which build fine with Ant, deploys perfectly to JBoss, and runs without any trouble. This project includes a few custom tag libraries (which is not JSTL!), which are also working without any difficulties.

The problem is with the Eclipse IDE (Ganymede): in every single JSP file which uses our custom tags, the JSP parser flags the taglib include line with with this error:

Cannot find the tag library descriptor for (example).tld

This also causes every use of the tab library to be flagged as an error, and since the IDE doesn't have their definition, it can't check tag parameters, etc.

Our perfectly-working JSP files are a sea of red errors, and my eyes are beginning to burn.

How can I simply tell Eclipse, "The tag library descriptor you are looking for is "src/web/WEB-INF/(example)-taglib/(example).tld"?

I've already asked this question on the Eclipse support forums, with no helpful results.

In Eclipse Helios "Java EE Module Dependencies" in the project properties has been replaced with "Deployment Assembly".

So for solving this problem with Eclipse Helios, the way I did it is the following:

• Right click on the project in package explorer and choose "Import..."
• Accept the default selection "File System" and press "Next"
• Press "Browse" in the From directory line, go to your tomcat installation and locate the file webapps/examples/WEB-INF/lib (I have tomcat 6, other versions of Tomcat may have the path webapps/jsp-examples/WEB-INF/lib). Once in the path press OK.
• Click besides jstl.jar and standard.jar to activate the check boxes
• On the line Into folder click on Browse and choose the library folder. I use /lib inside the project.
• Click "Finish"
• Right click on the project in Package Explorer view and choose properties (or press Alt + Enter)
• Click on "Java Build Path"
• Click "Add Jar", click on your project, folder lib, select jstl.jar, press OK
• Click "Add Jar", click on your project, folder lib, select standard.jar, press OK
• Press OK to dismiss the properties dialog
• Click on the Problems view and select the message "Classpath entry .../jstl.jar will not be exported or published. Runtime ClassNotFoundExceptions may result.".
• Right click on it and select "Quick Fix".
• Accept the default "Mark the associated raw classpath entry as a publish/export dependency" and press Finish.
• Do the same for standard.jar

This solves the problem, but if you want to check what has happened in "Deployment Assembly", open the project properties again, select "Deployment Assembly" and you'll see that standard.jar and jstl.jar have been added to WEB-INF/lib folder.

This was my problem and how I fixed it...

I had done everything everyone had mentioned above etc. but was still getting this error. Turns out I was using the uri's of http://java.sun.com/jsp/jstl/fmt and http://java.sun.com/jsp/jstl/core which were incorrect.

Try switching the uris from above to:

http://java.sun.com/jstl/fmt
http://java.sun.com/jstl/core

Also, make sure you have the correct jars referenced in your class path.

I had the same problem with a stripes taglib uri showing as not found. I was using Indigo and Maven and when I checked Properties->Java Build Path->Order & Export Tab I found (on a fresh project checkout) that the "Maven Dependencies" checkbox was unchecked for some reason. Simply checking that box and doing a Maven clean install cleared all the errors.

I wonder why Eclipse doesn't assume I want my Maven dependencies in the build path...