Does servlet engine read the whole request before

问题:

Servlet engine (e.g. Tomcat or Jetty) receives an HTTP request and calls a servlet with an HttpServletRequest object, which contains an InputStream of the request body.

Now I wonder if the engine has already read the whole request from the network and the InputStream is just a buffer in memory or it has read the request partially and when the servlet calls the InputStream.read it actually reads the socket.

回答1:

Usually that's not the case, because the request body can be really huge. A servlet container MAY do that if the content length is known and is small enough.

回答2:

It has to, at least in the case of POST, so it can form the requestParameterMap from the name-value pairs in the body of the request.