Access to ServletContext from PushStrategy - jetty

Question

I try to implement a custom PushStrategy, which is an API related to server push support of SPDY protocol inside Jetty.
I implement the following method:
public Set<String> apply(Stream stream, Fields requestHeaders, Fields responseHeaders);
However I need to access the ServletContext inside the method call but I don't know how I can access it.
I'm investigating a way to inject the WebAppContext in jetty.xml:
<New id="pushStrategy" class="spdy.MyPushStrategy">
<Set name="webAppContext">
<Ref id="..." />
</Set>
</New>
The problem is that this configuration step is in the Server block declared in jetty.xml:
<Configure id="Server" class="org.eclipse.jetty.server.Server">....</Configure>
while WebAppContext is configured in jetty-web.xml
<Configure id="WebAppContext" class="org.eclipse.jetty.webapp.WebAppContext">
I don't know how to refer any existing WebAppContext ID in this file.
Here is my maven plugin config:
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>${jetty-version}</version>
<configuration>
<stopPort>8888</stopPort>
<stopKey>quit</stopKey>
<jvmArgs>
-Xbootclasspath/p:${settings.localRepository}/org/mortbay/jetty/npn/npn-boot/${npn-version}/npn-boot-${npn-version}.jar
</jvmArgs>
<webAppConfig>
<jettyEnvXml>${basedir}/src/main/config/jetty-web.xml</jettyEnvXml>
</webAppConfig>
<jettyXml>${basedir}/src/main/config/jetty.xml</jettyXml>
<contextPath>/</contextPath>
</configuration>

Answer 1

When you create a WebAppContext via an XML file, such as what is described in the Configuring a Specific WebApp Deployment.
You can configure an id attribute for that particular webapp's <Configure> element.
Example:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN"
"http://www.eclipse.org/jetty/configure_9_0.dtd">
<Configure id="myapp1" class="org.eclipse.jetty.webapp.WebAppContext">
<Set name="contextPath">/wiki</Set>
<Set name="war">/opt/myapp/myapp.war</Set>
</Configure>
Then you can use the Jetty XML notation you described to reference that particular webapp.
<New id="pushStrategy" class="spdy.MyPushStrategy">
<Set name="webAppContext">
<Ref id="myapp1" />
</Set>
</New>
Now, back to your more specific concern, access to the ServletContext from the PushStrategy implementation.
That cannot be done from a PushStrategy implementation, as it is too high-level in the layering of the TLS -> SPDY (with PushStrategy) -> Connector -> Connection -> HTTP -> Request -> Handlers -> WebAppContext -> ServletContext -> Servlet.
You might be able to split up the behavior though.
Create a CustomPushFilter that your Servlet context has, it has the logic on what you want to associate for the push, done via a custom response header. Then your CustomPushStrategy could look for those response headers to know how to associate those extra resources. Bonus with this approach is that your Servlets could even automatically add resources for push based on servlet specific knowledge.