Evaluation of gwt.xml

I'm new to GWT and trying to understand the role of gwt.xml. The documentation says that one can specify things like <replace-with ... > where you can specify different implementations based on, say, the c开发者_Python百科urrent user agent. My question is: who evaluates these rules and when? What part of the execution stack deals with gwt.xml? Can the rules be modified runtime, by the way?

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You are talking about deferred-bindings.

• Compiler evaluates these rules --at compile time of course-- and depending on the parameters, creates or selects a specific implementation. See deferred bindings documentation for more detailed information.
• Again compiler
• They cannot be modified at runtime however depending on your use case there a lot of libraries to make things configurable/dynamic at runtime. If you can provide a use case, I am sure we can find something to help you.