Message filters are Spring Integration components, which act as an interceptor and decide whether to pass on the message to the next channel/component or drop it. Unlike routers, which decide what should be the next channel for a message, filters only take a boolean decision—whether to pass or not. There are two ways to define a message filter in Spring Integration:
Write a simple Java class and designate its method that will take decisions whether to pass the message or not
Configure it as a message endpoint that delegates to an implementation of the
MessageSelectorinterface
This can be configured either in XML or annotations can be used.
Let's take an example of using a simple Java class as a filter—this is part of our example about feeds. As feeds come in, we try to validate whether the payload is empty or not—then only pass it on for further processing:
<int:filter input-channel="fetchedFeedChannel" output-channel="filteredFeedChannel...