This valve encapsulates the basic behavior of the StandardHost. It has two primary responsibilities:

  • It invokes the pipeline of the appropriate Context to process the request
  • It handles any exceptions that occur during the processing of the request

This valve's invoke() method first obtains the Context associated with the incoming Catalina Request.

It then sets the context class loader of the current Thread to the ClassLoader associated with that Context. This ensures that any class loading will occur in the context of the selected web application, and so will get a view of the world as described by the WEB-INF/lib and WEB-INF/classes folders of that application.

It then invokes the pipeline associated with that Context as follows: ...

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