GWT 2.7 Dev mode and JDK6 Error

[San]

I am getting the below error when run simple GWT demo app in Dev mode using JDK6, but dev mode works fine with JDK7. I am using Chromium + GWT plugin. Is 2.7 GWT Dev mode supported only on JDK7+?. Eventually, I will switch to Super dev mode.

[ERROR] [gwt27demo] - Unable to load module entry point class com.google.gwt.user.client.DocumentModeAsserter (see associated exception for details)

[ERROR] [gwt27demo] - Failed to load module 'gwt27demo' from user agent 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2192.0 Safari/537.36' at 127.0.0.1:49436

12:06:38.522 [ERROR] [gwt27demo] Unable to load module entry point class com.google.gwt.user.client.DocumentModeAsserter (see associated exception for details)

java.lang.RuntimeException: Deferred binding failed for 'com.google.gwt.user.client.DocumentModeAsserter$DocumentModeProperty' (did you forget to inherit a required module?)

    at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:53)

    at com.google.gwt.core.shared.GWT.createImpl(GWT.java:83)

    at com.google.gwt.core.client.GWT.create(GWT.java:86)

    at com.google.gwt.user.client.DocumentModeAsserter.onModuleLoad(DocumentModeAsserter.java:88)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

    at java.lang.reflect.Method.invoke(Method.java:597)

    at com.google.gwt.dev.shell.ModuleSpace.onLoad(ModuleSpace.java:423)

    at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)

    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:530)

    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:368)

    at java.lang.Thread.run(Thread.java:662)

Caused by: java.lang.UnsupportedClassVersionError: com/google/gwt/user/client/DocumentModeAsserter_DocumentModeProperty : 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.lang.ClassLoader.defineClass(ClassLoader.java:465)

    at com.google.gwt.dev.shell.CompilingClassLoader.findClass(CompilingClassLoader.java:1142)

    at com.google.gwt.dev.shell.CompilingClassLoader.loadClass(CompilingClassLoader.java:1215)

    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

    at java.lang.Class.forName0(Native Method)

    at java.lang.Class.forName(Class.java:249)

    at com.google.gwt.dev.shell.ModuleSpace.loadClassFromSourceName(ModuleSpace.java:683)

    at com.google.gwt.dev.shell.ModuleSpace.rebindAndCreate(ModuleSpace.java:486)

    at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:49)

    at com.google.gwt.core.shared.GWT.createImpl(GWT.java:83)

    at com.google.gwt.core.client.GWT.create(GWT.java:86)

    at com.google.gwt.user.client.DocumentModeAsserter.onModuleLoad(DocumentModeAsserter.java:88)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

    at java.lang.reflect.Method.invoke(Method.java:597)

    at com.google.gwt.dev.shell.ModuleSpace.onLoad(ModuleSpace.java:423)

    at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)

    at com.google.gwt.dev.shell.BrowserChannelServer.processConnectio

    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChann

[wade...@gmail.com]

San,
Did you get this problem solved? I have the same issue. Please let me know if you know the solution.
Thanks

[Kirill Prazdnikov]

Is there any reason using JDK 6 ? 

Why not JDK 5 or 4 ?