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If I understood you correctly, you have a REST-like API on another servlet, and want to use this in your Vaadin application. This is NOT a Vaadin feature, and Vaadin does not provide any methods for you to access these. The open()-call you are using sends a browser redirect to the vaadin client side, which is not what you are after here. You need to use a 3rd part library or the Java interfaces for making HTTP calls.