How does jboss server handles migrated .ear and .war files?

Question

I am turning to SO here as my last resort, since my situation has been so illogical that I am at my wits end, even google can't get me a relatively close response.

I'll have to be very chronological. I am maintaining an application in Eclipse. The way application changes apply to the website is when I deploy appropriate .ear and .war files in the jboss test server.

I was relatively new to this whole process, so while learning on this, I stumbled upon occurrence I simply cannot logically comprehend.

1) I made some changes to the application (let's call it changeset_1 for convenience), created appropriate .ear and .war files, deployed them to the jboss server.

2) Website was returning error 500. No biggie, I thought, let's deploy working files back to server. It returned the same error as if I didn't deploy originals at all.

3) Restarting jboss server did not accomplish anything.

4) Frustrated, I thought of creating alternate files from the latest deployment directory. So I stored working project directory in the folder neighboring workspace folder used by eclipse. Then I started a new instance of Eclipse, and name new folder as a main namespase (old instance still uses old namespace folder).

5) In a new instance, I did not do any changes, I was just following the same steps as before to create appropriate .ear and .war files and deployed them as is to the server.

Now here is an interesting part

After performing steps above, I went to the test site link, and what I saw was: All changes from changeset_1 which I made originally in the first step successfully applied! At the same time, my last deployment was completely ignored.

Can anyone please point me in the right direction on how to approach such situation? Do I miss some kind of fundamental understanding on how all this stuff operates?

I literally don't have any more place to turn to... Unless I could not comprehend such incident to the point I could not explain it properly to google and it was giving me wrong results. Any help is really appreciated!

PS: I will do my best to provide any additional details if needed.

IMPORTANT EDIT

I initially thought I might've missed or misunderstood something, so I have recreated the scenario above for the second time. And for the second time I got the same outcome. Which no longer makes it an accident, but persistent occurrence.

EDIT 2

Upon request, here is a full error log in log file

2016-10-20 08:11:34,492 WARN
[org.jboss.detailed.classloader.ClassLoaderManager] (http-0.0.0.0-8080-1)
Unexpected error during load of:gov.ca.chp.cvs.struts.forms.CVSForm
java.lang.UnsupportedClassVersionError: Bad version number in .class file
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
    at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:63)
    at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:572)
    at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:532)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:530)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:507)
    at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:134)
    at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131)
    at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:452)
    at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:251)
    at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:150)
    at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:265)
    at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:1119)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:798)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:441)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
    at org.apache.struts.config.FormBeanConfig.formBeanClass(FormBeanConfig.java:358)
    at org.apache.struts.config.FormBeanConfig.createActionForm(FormBeanConfig.java:212)
    at org.apache.struts.util.RequestUtils.createActionForm(RequestUtils.java:292)
2016-10-20 08:11:34,492 WARN
[org.jboss.detailed.classloader.ClassLoaderManager] 
(http-0.0.0.0-8080-1) Unexpected error during load of:gov.ca.chp.cvs.struts.forms.CVSForm
java.lang.UnsupportedClassVersionError: Bad version number in .class file
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
    at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:63)
    at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:572)
    at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:532)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:530)
    at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:507)
    at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:134)
    at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131)
    at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:452)

Answer 1

Rootcause: "java.lang.UnsupportedClassVersionError: Bad version number in .class file" comes when you compile a Java class in higher version of Java Compiler and run it on lower version of JRE.

Read more: http://javarevisited.blogspot.com/2011/12/bad-version-number-in-class-files-cause.html#ixzz4NjV9ORkF