This module interfaces with the TLS implementation of Oracle JDK8 to provide an implementation of ALPN. The module was written for use in Grizzly, but is intended as a general purpose solution to allow JDK8 based software to use ALPN.
How Grizzly Uses This Module
Grizzly has the concept of an AddOn
. This facility allows Grizzly to be extended using an implementation of the Chain of Responsibility design pattern. In general, an AddOn
implementation will insert one or more Filter
implementations into the FilterChain
which is used to process HTTP requests and cause HTTP responses to be sent.
Grizzly itself uses this AddOn
concept to provide HTTP/2 support, in the form of Http2AddOn
In addition to registering filters for HTTP/2 processing, this AddOn
implementation registers a callback withthe ALPN extension to insert itself into the SSL Handshake process
Programmatic Configuration
AddOn
has a setup
method that is called to allow the implementation to do whatever one-time setup is required to make things work. The setup
override in the Http2AddOn
takes the following actions if the current connection is secure (that is, it is supposed to be using ALPN).
-
Use the
addHandshakeListener
method of the existingSSLBaseFilter
to cause an ALPN specific SSL handshake listener to be added to the existing list of listeners that are invoked when an ssl handshake happens.Grizzly's handshake listener has several methods, but the only one used is
onStart
. This obtains the JDKSSLEngine
and takes different action depending on the return from itsgetUseClientMode()
method. Thegrizzly-npn
module providesAlpnClientNegotiator
andAlpnServerNegotiator
interfaces for these two cases. Please see the interfaces for the specification of the required actions.If
getUseClientMode
is true,-
use the grizzly
addCloseListener
facility to install a listener that callsNegotiationSupport
.removeClientNegotiator()
. This will ensure the client negotiator is removed when the connection closes. -
Call
NegotiationSupport.addNegotiator
passing theSSLEngine
and the client negotiator impl.
If
getUseClientmode
is false,- do the same as above, but use the server negotiator impl.
By the time
onStart
is invoked, the handshake listener will have been initialized with implementations ofAlpnClientNegotiator
andAlpnServerNegotiator
by theHttp2AddOn
. -
Deployment Configuration
The above programmatic configuration steps will make it so the simple act of including the module built from the bootstrap
sub-module of this repository in the bootclasspath of the JVM will enable ALPN support in that JVM.