Java.lang.ClassNotFoundException: org.quartz.DisallowConcurrentExecution

I've developed some code that executes a quartz job.At first the code was outside the tomcat and it executes very well, but when I tried to embed the same code inside a web application I get java.lang.NoClassDefFoundError: org/quartz/DisallowConcurrentExecution.
I'm using quartz 2.1.5 and it's already in the class path.
Here is the stack trace:

Exception in thread "DefaultQuartzScheduler_QuartzSchedulerThread" java.lang.NoClassDefFoundError: org/quartz/DisallowConcurrentExecution
INFO: Illegal access: this web application instance has been stopped already.  Could not load org.quartz.DisallowConcurrentExecution.  The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
        at org.quartz.impl.JobDetailImpl.isConcurrentExectionDisallowed(JobDetailImpl.java:390)
java.lang.IllegalStateException
        at org.quartz.simpl.RAMJobStore.acquireNextTriggers(RAMJobStore.java:1447)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1273)
        at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:264)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
Caused by: java.lang.ClassNotFoundException: org.quartz.DisallowConcurrentExecution
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387)
        at org.quartz.impl.JobDetailImpl.isConcurrentExectionDisallowed(JobDetailImpl.java:390)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
        at org.quartz.simpl.RAMJobStore.acquireNextTriggers(RAMJobStore.java:1447)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
        at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:264)
Related Solutions
Java.lang.NoClassDefFoundError: org/springframework/web/servlet/HttpServletBean : org/springframework/context/EnvironmentAware

If it works for an older version(as you say), What I guess there are some places you have old jar in the path, which mess up the jar dependency 
I will suggest you do a full disk search to find out all your spring jar location and clean them up.
BTW: you can try to add jar to tomcat/lib to try also (it is not proper practice, but this can help to find out whether it is path related issue).
    
Java – HTTP 400 Bad Request : javax.ws.rs.BadRequestException

Your resource is returning an instance of Weightings, so you just need to cast it, you don't need to do the addAll()
Weightings weightings = new Weightings();
 weightings.getWeightings().addAll((Collection<? extends Weighting>) webTarget.path("rest").path("report").path("loadWeightingByPlate").
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Should be:
Weightings weightings = (Weightings) webTarget.path("rest").path("report").path("loadWeightingByPlate").
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It won't fix your 400 exception, but you'll get a ClassCastException without it.