Develop Reference

NoClassDefFoundError for com.cloudant.client.api.ClientBuilder but class exists

Project returns error Error 500: javax.servlet.ServletException:
java.lang.NoClassDefFoundError: com/cloudant/client/api/ClientBuilder
But class exists.
Error below (removed project's name).
Here is the dependency
I've already tried an mvn clean install -U, removing the .m2
folder and still no luck so far.
Eclipse version is Version: 2018-12 (4.10.0).
My computer is macOS High Sierra 10.13.6

No class definition found error indicates that your Java runtime could not find the class in question. Please check if your app is deployed to the runtime which you think it should be deployed.
Mostly this would be linked to any of the following steps in you project life cycle.
1. Build (turn on 'build automatically') in Eclipse. I see you've done these steps.
2. Deployment to target runtime (like deploying to some web container). Check if your code is being deployed or not to target runtime.
But I see that you've already mentioned that it works for sometime, which means that you need to understand why the runtime is unable to access your class at that moment. I would do the following.
1. Check if JAR is already present.
2. If not present, follow the build deploy steps you've followed. This means that you'll have to establish how the JAR mysteriously got deleted.
3. If JAR is present, but you see this error, then it means that your runtime CLASSPATH has mysteriously changed and that needs to be investigated. Ideally this should not happen, as all softwares usually are 'consistant', i.e. they either consistently have error or consistently work. This inconsistency itself indicates something environmental which you need to crack.
Is that IBM WebSphere? If this is in your company and it is a shared server or something, check if someone is inadvertently fiddling with your deployment or something.
Good luck!
Edit: Check if this helps you conceptually - NoClassDefFoundError by switching to another project

Why does my deployed eclipse plugin throws NoClassDefFoundError exception?

I'm asking and answering this question to save me from going down this rat hole again in the future.
I'm building a cross platform eclipse IDE based software development environment with about 40 plugins. When I installed the latest nightly build and did some testing on my Linux test system the application started throwing the dreaded java.lang.NoClassDefFoundError when I did a certain action. This was not happening on my Windows installation. It did not happen in my development environments on Linux or Windows. This action and the code behind it is new and so not yet covered in our automated test suite.
The plugin throwing the exception was trying to access a static class method in another plugin, but failing to find the class. Things I tried:
First thought: static initializer fails for some reason! Nope. I can see other plugins access this static class and methods prior to the failure (by attaching my debugger to the installed instance of my product and stepping through the code).
The fact that it works from other plugins eliminate the other usual reason for failure, not properly exporting the package. It was exported correctly.
I poured over my plugin dependency list, comparing them to plugins that were able to access the offending class, but with no success. All dependencies were accounted for.
I did a deep dive into my MANFEST.MF. I switched from using "Required-Bundle" to "Import-Package" in the MANIFEST.MF. That created new problems for me so I reverted that change. Everything looked good.
My build.properties looked good. Not too much in there to go wrong. It was consistent with my MANFIEST.MF where it counts.
I deconstructed my plugin on the installed instance to be sure that the class was indeed present. It was.
Everything was configured correctly. Everything!
I poured over many related SO questions and blog posts but none of them offered a solution that worked or any additional insight into the problem.
The next step was to start iterating over my nightly builds to find the build where the problem first showed up. Once I identify that build, I'd be able to iterate over all the commits from the day before, doing full builds, then installs to find the commit that broke it.
I started 10 days prior and installed every nightly build. All the way up to the build that failed in my test environment. Every single one of them worked. Why?. See my answer below (or submit you own).

When testing a new eclipse IDE build make sure you start with a fresh new non-existent workspace directory and use the "-clean" command line parameter to flush any caches that survive from a previous installation.
The failure was happening because I (1) failed to delete my previous workspace directory before starting the application; and (2) did not use the "-clean" command line parameter to delete related cached information; and (3), even "-clean" may not be enough, I also removed the entire application directory (which, in turn, removed the 'configuration' directory and all cached data within that may not have been "cleaned" by the "-clean" command line argument).
I had been refactoring a few class names to have more meaningful names. When I ran the product with an existing environment the product was using cached data, getting the old name of a class that had been renamed, and failing to resolve it. (You might think that seeing the old name was a good clue, but, unfortunately, one of the first things I tried was undoing the class name refactoring, thus restoring the previous name. So the error reported the correct name, but, I suspect, there is a signature of sorts that did not resolve.)
Of course it is a best practice to always start with a new workspace when testing. I've been doing Eclipse IDE development for years and I know this well. But yesterday I forgot (not helped by the fact that my Windows installation did not suffer the same error for whatever reason). You will forget on occasion...and it will bite you.

Unable to run wsimport utility in JDK8

I have JDK8 installed in the directory C:\Program Files\Java\jdk1.8.0_05\ and I have my PATH Environment Variable set to C:\Program Files\Java\jdk1.8.0_05\bin.
Now; in order to use Amazon's Product API I follow their guidelines here under the Java getting set up section; and I use the following command...
wsimport -d ./build -s ./src -p com.ECS.client.jax http://webservices.amazon.com/AWSECommerceService/AWSECommerceService.wsdl -b jaxws-custom.xml
after opening a command prompt in a custom directory I created on my desktop; that custom directory contains the build and src directories as specified in the instructional page provided by Amazon.
Now when I run the command aforementioned; I receive the error...
'wsimport' is not recognized as an internal or external command
however; if I run Java -version within the same command prompt all works well and as expected.
Not sure where to go from here or why it isn't reading through?
Note I already attempted the solutions at this page; to no avail.

I found this in the comments section of the following article. I include it here in full because I think it explains why your JDK8/wsimport fails to build and consequently why it works when you switch back to Java7.
http://blog.takipi.com/6-reasons-not-to-switch-to-java-8-just-yet/
Even though the article was written over 3 years ago, I am still having java8/wsimport problems (2017).
Why not mention some more obvious ones:
The new defaults in Javadoc (called doclint) will break your build. In particular if you are using Maven and some kind of CI (e.g. Hudson,
Jenkins) you'll quickly realize that you can't just take your project
and build in JDK8. Your build will almost certainly error out because
of the new Javadoc. (I have yet to see a project that didn't). The
reason is that in Maven a return error code from the javadoc tool will
stop the whole release process ... and as I said I have yet to see a
project that would not somewhere have a Javadoc doclint noncompliance.
Most larger projects (e.g. Netty) seem to solve the problem by simply
turning off doclint (which of course wasn't the idea behind doclint)
or they stay on JDK7 for a while longer until they iron out all their
comments problems.
Code generation tools in JDK8 (e.g. wsimport) produce code that is not doclint compliant. This is a clear bug and well documented. It
means that one part of the JDK8 is not working with another part of
the JDK8. Expect to have to circumvent this somehow if you have a web
consumer application.

Eclipse Java Remote Debug: How do I ensure that the code I've got in my project is the same as the code running in the JVM?

I've got some existing source code, and jars for a webapp. I am attempting to run the webabb using tomcat and then remote debugging the tomcat server using eclipse to figure out what is happening with the webapp.
For some reason however, eclipse refuses to trap any breakpoints. I've compared the md5sums of the jars on the server with the ones I've got in my debug project, and they match.
Is there some way I can ask eclipse to reconcile the java classes in the remote JVM with the java classes in the local jars and make sure they correspond. Or, perhaps, more specifically, whether the code associated with breakpoints I've set have actually be loaded into the remote JVM?

Check that on the Java Compiler properties page for the java projects in question that the class file options are all checked (you only need the first three but having all five checked is a good thing for debugging)

Headless Eclipse Build returns ERRORLEVEL 13

Everything was going well. Nightly builds ran for more than a month with no problems. However, suddenly when invoking the feature builder from Eclipse the execution ends right away with the message.
ERRORLEVEL 13
As far as I know I haven't changed anything, as this computer is normally not touched. (It is only used for the nightly builds).
I've googled around to see what this error means but to no avail. I found a link from IBM that shows a custom bat file that catches this error, but the explanation given is not very useful.
My guess is that this is related to the workspace, somehow, or that the whole eclipse installation is corrupted.
Do you have any idea what this error means and how can it be corrected?

After reading what the error code means thanks to the answer from VonC I understood where to look. The problem was a lot more obscure that it seems.
I looked into the configuration folder for Eclipse (logs are either written there or in the .metadata folder when something goes wrong), and I found a huge log file. Inside the file I found the following error:
application org.eclipse.sdk not found
and the following exception, followed by a plugin name, several times:
java.util.zip.ZipException: Too many open files
Several plugins could not be loaded, causing a cascade of missing dependencies that prevented Eclipse from launching. I searched the web for this exception and found the following bug description from SUN, which says that Java 1.5.0 can not open more than 2,100 zip files.
The problem started a while after I installed the BABEL project translations for Eclipse into the build computer. These are more than 900 fragments, containing translations for many plugins, one for each language. As I installed it on top of an existing eclipse installation, it seemed that it was not a problem to open them.... until I cleared the workspace for the builds. Then Eclipse wouldn't launch anymore. I went over the limit. It didn't help that the first thing I tried to fix the build was, again.... clearing everything.
Because I only use this computer for headless builds, I didn't realize that the problem was in Eclipse itself and I was looking inside the build process. I only realized when I looked into the log file.
After installing Java 1.6.0_11 I was able to launch Eclipse and go on with my build.

It should mean "ant build failed", meaning the headless ant script fails at some point.
You should check if you can catch the log/output generated by this script to analyze this ant session and see at what point the ant script fails.
If it fails right away, it usually is because of:
a change in rights (writing access), or
in environment variable modifications, or
in resource access (path non accessible).
You also have to check if the computer is still in its original windows domain, and if the rights (admin ?) associated with the account running the ant script are still the same.