JBO-25004: Definition name of type Form Binding Definition is invalid @ADF

I got following error message when i ran my application first time:

oracle.jbo.InvalidDefNameException: JBO-25004: Definition name sessiondef.3App_CancelButton.CancelButttonPageDef of type Form Binding Definition is invalid.
at oracle.jbo.mom.DefinitionManager.validateSessionDefName(DefinitionManager.java:509)
at oracle.jbo.mom.DefinitionManager.findSessionDefObject(DefinitionManager.java:548)
at oracle.adf.model.binding.DCBindingContainerDef.findSessionDefObject(DCBindingContainerDef.java:328)
at oracle.adf.model.binding.DCBindingContainerDef.findDefObject(DCBindingContainerDef.java:290)
at oracle.adf.model.binding.DCBindingContainerReference.getDef(DCBindingContainerReference.java:107)
at oracle.adf.model.BindingContext.findBindingContainerDefByPath(BindingContext.java:1555)
at oracle.adf.model.BindingRequestHandler.isPageViewable(BindingRequestHandler.java:371)
at oracle.adf.model.BindingRequestHandler.beginRequest(BindingRequestHandler.java:247)
at oracle.adf.model.servlet.ADFBindingFilter.doFilter(ADFBindingFilter.java:189)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)

In my case, the reason of above error was wrong package name ie 3App_CancelButton. I created a page in a folder named 3App_CancelButton under web content and generated its page definition file. The file was generated it self under package named 3App_CancelButton, which is not a valid package name. To remove this, rename the package using Refactor->Rename to a valid name.