Allow for customization of the Jetty WebAppContext

Standalone Jetty installations provide a means to configure the context via XML files: https://jetty.org/docs/jetty/12/operations-guide/xml/index.html

The mechanism doesn't work for embedded use - XML files need to be discovered and loaded explicitly. For our purposes, applications can place a jetty-context.xml file in their WEB-INF directory in order for Alpine to discover them.

Since Alpine applications do not directly depend on alpine-executable-war, and thus do usually not have access to Jetty classes, the Jetty-native XML configuration was preferred over programmatic customization.

Signed-off-by: nscuro <nscuro@protonmail.com>

alpine-executable-war/src/main/java/alpine/embedded/EmbeddedJettyServer.java

@@ -28,6 +28,9 @@
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
 import org.eclipse.jetty.util.Callback;
+import org.eclipse.jetty.util.resource.Resource;
+import org.eclipse.jetty.util.resource.URLResourceFactory;
+import org.eclipse.jetty.xml.XmlConfiguration;
 import org.slf4j.Logger;
 import org.slf4j.bridge.SLF4JBridgeHandler;
 
@@ -93,6 +96,19 @@ public static void main(final String[] args) throws Exception {
         final URL location = protectionDomain.getCodeSource().getLocation();
         context.setWar(location.toExternalForm());
 
+        // Allow applications to customize the WebAppContext via Jetty context XML file.
+        // An example use-case is the customization of JARs that Jetty shall scan for annotations.
+        //
+        // https://jetty.org/docs/jetty/12/operations-guide/xml/index.html
+        // https://jetty.org/docs/jetty/12/operations-guide/annotations/index.html
+        final URL jettyContextUrl = Thread.currentThread().getContextClassLoader().getResource("WEB-INF/jetty-context.xml");
+        if (jettyContextUrl != null) {
+            LOGGER.debug("Applying Jetty customization from {}", jettyContextUrl);
+            final Resource jettyContextResource = new URLResourceFactory().newResource(jettyContextUrl);
+            final var xmlConfiguration = new XmlConfiguration(jettyContextResource);
+            xmlConfiguration.configure(context);
+        }
+
         server.setHandler(context);
         server.addBean(new ErrorHandler());
         try {

pom.xml

@@ -157,7 +157,7 @@
         <plugin.cyclonedx.outputReactorProjects>true</plugin.cyclonedx.outputReactorProjects>
 
         <!-- Dependency Versions -->
-        <lib.alpine.executable.war.version>3.0.2-SNAPSHOT</lib.alpine.executable.war.version>
+        <lib.alpine.executable.war.version>3.1.0-SNAPSHOT</lib.alpine.executable.war.version>
         <lib.angus-mail.version>2.0.3</lib.angus-mail.version>
         <lib.bcrypt.version>0.4</lib.bcrypt.version>
         <lib.caffeine.version>3.1.8</lib.caffeine.version>