Just create a my test canvas app with heroku and all looks good with my developer account. Is it possible to create canvas app without using heroku. We use google app engine to host and manage our application . If canvas app would work with external server This will help us to maintain our app easily for future release and bug fix. Please let me know if you need more detail on this.
Sure. Here's a Java framework on GitHub that should provide an example for you https://github.com/forcedotcom/SalesforceCanvasFrameworkSDK it even has in the readme how to build it locally before deploying it to "heroku or any other server"