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How to use client side module
I created a bunch of java files by using the vaadin wideget wizzard, and deinfe a entrypoint class, it can compile success, but when access the result page, the browser said 'There is no information about interface com.geocom.administration.web.ui.login.client.logincomponent.LoginComponentServerRpc. Did you forget to compile the widgetset?'
It does have a file called LoginComponentServerRpc, how to resolve this
I'm not 100% certain whether you are talking about successful java compilation or widgetset compilation, so just in case:
Whenever you add or modify client-side classes you'll need to recompile your widgetset, e.g. by calling mvn install or clicking the compile widgetset -button in Eclipse. If you were using the default widgetset before, that won't be an option with client-side changes -- you'll need a YourWidgetsetName.gwt.xml -file in package com.geocom.administration.web.ui.login (or one of its parent packages) before you can recompile the widgetset, and your UI must be configured to use that widgetset.
That said, even if you've done all that, and your widgetset compilation has finished successfully, it's possible that something went wrong with the compilation of that particular class. Make sure to configure the widgetset compilation to 'strict', and check the console log in case there was anything suspicious that might have caused the compilation to skip that particular class. If everything else fails, temporarily remove absolutely everything non-essential from that file, and see if the compilation works then. Sometimes e.g. using an import that GWT doesn't support, or having a JavaDoc @link reference to a server-side class, might silently cause the file to be dropped.