java.lang.UnsupportedClassVersionError: test_hello_world :
 Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)

Why this Happens?
When you did maven build in Java 8 and try to deploy the ear file in Server which uses Java 1.7 then this issue happens.Error means you’re trying to load a Java “class” file that was compiled with a newer version of Java than you have installed.For example, your .class file could have been compiled for JDK 7, and you’re trying to run it with JDK 6.You must have compiled your code with a higher version and trying to run it using a lower version

Solution

Window -> Preferences -> Java -> Compiler and then set "Compiler compliance level" to 1.7

Jboss Timeout during deployment
Add the below entries in Standalone xml file
Standalone.xml

<subsystem xmlns="urn:jboss:domain:deployment-scanner:1.0">
    <deployment-scanner scan-interval="5000" relative-to="jboss.server.base.dir" path="deployments" deployment-timeout="1000" />
</subsystem>

deployment-timeout=”1000″ is set to 1000 seconds.

Suppressing Errors in JBOSS using ID

JBAS011006: Not installing optional component org.springframework.web.context.request.async.StandardServletAsyncWebRequest due to exception: org.jboss.as.server.deployment.DeploymentUnitProcessingException

Standalone.xml

<subsystem xmlns="urn:jboss:domain:logging:1.1">
      <console-handler name="CONSOLE">
          <filter>
              <not>
                  <match pattern="JBAS011054|JBAS011006"/>
              </not>
          </filter>
      </console-handler>
  </subsystem>     

JBOSS clearing Temp Files
Parameters to be set when server VM start

-Djboss.vfs.cache=org.jboss.virtual.plugins.cache.IterableTimedVFSCache 
-Djboss.vfs.cache.TimedPolicyCaching.lifetime=1440

JBOSS Config parameters

jboss.home.dir - The base directory of the jboss distribution - default: $JBOSS_HOME
jboss.home.url - The base url of the jboss distribution - default $JBOSS_HOME
jboss.lib.url - The url where the kernel jars exist - default: $jboss.home.url/lib
jboss.patch.url - A directory where patch jars exist - default: none
jboss.server.name - The configuration name of the server - default: default
jboss.server.base.dir - The directory where server configurations exist - default: $jboss.home.dir/server
jboss.server.base.url - The url where server configurations exist - default: $jboss.home.url/server
jboss.server.home.dir - The directory for the current configuration - default: $jboss.server.base.dir/$jboss.server.name
jboss.server.home.url - The url for the current configuration - default: $jboss.server.base.url/$jboss.server.name
jboss.server.temp.dir - The directory for temporary files - default: $jboss.server.home.dir/tmp
jboss.server.data.dir - The directory for data files - default: $jboss.server.home.dir/data
jboss.server.config.url - The url for configuration files - default: $jboss.server.home.url/conf
jboss.server.lib.url - The url for static jar files - default: $jboss.server.home.url/lib
jboss.server.log.dir - The directory where the server logs are written - default: $jboss.server.home.dir/log

For Example, if you want JBoss to write the server log file to “C:/Logs/”, then what you should do is to set a system property as this

 -Djboss.server.log.dir=C:/Logs/