| Re: [jetty-users] Register ServletRequestListener from OSGi Bundle |
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Jan, Thank you for replying. Here is the scenario: We have a FOSS project named Lucee, which is a Servlet based on
JSP, which allows for rapid development of web applications
because it's much simpler to use and easier to learn than JSP/JSF,
for example. The project is used by many developers and
organizations all over the world. Lucee allows for extensions (or plugins), which are loaded via
OSGi, so that they can be loaded/unloaded/updated on demand
without restarting the Servlet container, as well as use different
versions of the same 3rd party libraries side by side. I wrote an open source extension for Lucee which provides WebSocket support: https://github.com/isapir/lucee-websocket -- The extension has the following requirements: 1) Be packaged as an OSGi bundle so that it can be installed as a Lucee extension. 2) Be JSR-356 compliant because Lucee could run on any
Servlet container, so I can not use Jetty- or Tomcat- specific
APIs. 3) Allow for WebSocket configuration to be set at runtime, as we do not know in advance what endpoint etc. the developer will want to use. 4) Be able to communicate with the Lucee servlet for Application and Session states. In order to be able to retrieve the correct state from Lucee (requirement 4) my code needs to know the root directory of the ServletContext, e.g. servletContext.getRealPath("/"), at the Handshake phase. This is required so that multiple contexts can maintain their separate states without "mixing" up state between the contexts, so that if there are two contexts, ServletContext1 and ServletContext2, a user that connects to ServletContext2 he will get the state from that context, and not the one from ServletContext1.The only way that I found to retrieve the ServletContext through the JSR-356 spec (requirement 2) is via the HttpSession in ServerEndpointConfig.Configurator.modifyHandshake(), i.e. handshakeRequest.getHttpSession().getServletContext().getRealPath("/"). The problem is, that according to the JSR, the Session should not be initialized in handshakeRequest.getHttpSession() if one does not exist, so by default, handshakeRequest.getHttpSession() always returns null. The "recommended" way to initialize the Session is with a ServletRequestListener, where a simple call to httpServletRequest.getHttpSession() does initialize the HttpSession object. I have provided a class to do that -- https://github.com/isapir/lucee-websocket/blob/master/src/main/java/net/twentyonesolutions/servlet/listener/HttpSessionInitializer.java#L40 -- but because this is an OSGi bundle (requirement 1), this jar is not on the classpath -- and can not be specified as-is in the web descriptor. The solution that I came up with, is to add a tiny jar file to the classpath with a Servlet Filter that initializes the HttpSession -- https://github.com/isapir/servlet-filter-utils/blob/master/src/main/java/net/twentyonesolutions/servlet/filter/HttpSessionInitializerFilter.java#L70 -- Then the user adds the tiny jar to the classpath, and configures the Filter to intercept WebSocket URIs. But there has to be a simpler method than that, no? Again, my ultimate goal here is to get the ServletContext's root directory, so if there is another way to do that then I would not need to jump through all those hoops. If not, I am looking to register the ServletRequestListener so that the user will not need to add another jar and/or modify web.xml. Thank you, Igal Sapir Lucee Core Developer
On 7/14/2017 12:23 AM, Jan Bartel
wrote:
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