Unsupported Class Version Error

问题

While trying to call an EJB made using NETbeans (using jdk1.7) from a client made using Eclipse IDE (using jdk1.6), I am getting following error-

Exception in thread "main" java.lang.UnsupportedClassVersionError: stateless/TestEjbRemote : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at com.sun.ejb.EJBUtils.getBusinessIntfClassLoader(EJBUtils.java:688)
    at com.sun.ejb.EJBUtils.loadGeneratedRemoteBusinessClasses(EJBUtils.java:463)
    at com.sun.ejb.EJBUtils.lookupRemote30BusinessObject(EJBUtils.java:414)
    at com.sun.ejb.containers.RemoteBusinessObjectFactory.getObjectInstance(RemoteBusinessObjectFactory.java:75)
    at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
    at com.sun.enterprise.naming.impl.SerialContext.getObjectInstance(SerialContext.java:556)
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:514)
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:455)
    at javax.naming.InitialContext.lookup(InitialContext.java:392)
    at Main.main(Main.java:19)

Any solution to this problem ?

回答1:

Try to change the Target JRE version to 1.6 in Build Configuration.

回答2:

Problem was- I was calling EJB,made using jdk1.7 from client, which was using jdk1.6. Switched the jdk1.7 to jdk 1.6, it worked. or one can switch jdk1.6 to 1.7, then also it would work. Conclusion- u can call any EJB which is using either the same version or lower version of jdk as the caller.

回答3:

I had the same problem but I was using textpad though. The solution was pretty simple. Try placing the class in conflict on a different location (a backup folder perhaps whatever) or you can just simply delete it as long as it doesn't exist on the same directory. Then try compiling the java file so you can have a new class built to your computer's specification. Try if it works for you coz it worked for me. :)

回答4:

It's the second time I've had the issue, just change the build configuration of this project. Right click your project name --> [properties] --> [java compiler] --> [Enable project specific settings] --> set [compiler compliance level] to 1.7

Eclipse has it's own compiler, no matter which version of javac(jdk) in you system,so you must configure the version of eclipse compiler firstly.

Reference: java.lang.UnsupportedClassVersionError: Bad version number in .class file?

来源：https://stackoverflow.com/questions/9091713/unsupported-class-version-error