simplify the usage of WebSocketUpgradeFilter in jetty 10

jetty-servlet/src/main/java/org/eclipse/jetty/servlet/FilterHolder.java

@@ -36,6 +36,7 @@
 import javax.servlet.ServletResponse;
 
 import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.util.Loader;
 import org.eclipse.jetty.util.TypeUtil;
 import org.eclipse.jetty.util.component.Dumpable;
 import org.eclipse.jetty.util.component.DumpableCollection;
@@ -221,6 +222,39 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
         }
     }
 
+    /**
+     * Work out the class of the held {@link Filter} even before the {@link FilterHolder} has been started.
+     * @return the class of the held {@link Filter}, or null if not available.
+     */
+    @SuppressWarnings("unchecked")
+    public Class<? extends Filter> getFilterClass()
+    {
+        if (_filter != null)
+            return _filter.getClass();
+
+        Filter filter = getInstance();
+        if (filter != null)
+            return filter.getClass();
+
+        Class<? extends Filter> heldClass = getHeldClass();
+        if (heldClass != null)
+            return heldClass;
+
+        String className = getClassName();
+        if (className != null)
+        {
+            try
+            {
+                return Loader.loadClass(className);
+            }
+            catch (ClassNotFoundException e)
+            {
+                LOG.warn("Could not load filter class", e);
+            }
+        }
+        return null;
+    }
+
     @Override
     public void dump(Appendable out, String indent) throws IOException
     {

jetty-websocket/websocket-util-server/src/main/java/org/eclipse/jetty/websocket/util/server/WebSocketUpgradeFilter.java

@@ -40,7 +40,6 @@
 import org.eclipse.jetty.util.component.Dumpable;
 import org.eclipse.jetty.util.thread.AutoLock;
 import org.eclipse.jetty.websocket.core.Configuration;
-import org.eclipse.jetty.websocket.core.server.WebSocketServerComponents;
 import org.eclipse.jetty.websocket.util.server.internal.WebSocketMapping;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -78,34 +77,40 @@ public class WebSocketUpgradeFilter implements Filter, Dumpable
     private static final Logger LOG = LoggerFactory.getLogger(WebSocketUpgradeFilter.class);
     private static final AutoLock LOCK = new AutoLock();
 
+    /**
+     * The init parameter name used to define {@link ServletContext} attribute used to share the {@link WebSocketMapping}.
+     */
+    public static final String MAPPING_ATTRIBUTE_INIT_PARAM = "org.eclipse.jetty.websocket.util.server.internal.WebSocketMapping.key";
+
+    /**
+     * Return any {@link WebSocketUpgradeFilter} already present on the {@link ServletContext}.
+     *
+     * @param servletContext the {@link ServletContext} to use.
+     * @return the configured default {@link WebSocketUpgradeFilter} instance.
+     */
     private static FilterHolder getFilter(ServletContext servletContext)
     {
         ContextHandler contextHandler = Objects.requireNonNull(ContextHandler.getContextHandler(servletContext));
         ServletHandler servletHandler = contextHandler.getChildHandlerByClass(ServletHandler.class);
-
         for (FilterHolder holder : servletHandler.getFilters())
         {
-            if (holder.getInitParameter(MAPPING_ATTRIBUTE_INIT_PARAM) != null)
+            if (WebSocketUpgradeFilter.class.isAssignableFrom(holder.getFilterClass()))
                 return holder;
         }
-
         return null;
     }
 
     /**
-     * Configure the default WebSocketUpgradeFilter.
-     *
-     * <p>
-     * This will return the default {@link WebSocketUpgradeFilter} on the
-     * provided {@link ServletContext}, creating the filter if necessary.
+     * Ensure a {@link WebSocketUpgradeFilter} is available on the provided {@link ServletContext},
+     * a new filter will added if one does not already exist.
      * </p>
      * <p>
      * The default {@link WebSocketUpgradeFilter} is also available via
      * the {@link ServletContext} attribute named {@code org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter}
      * </p>
      *
-     * @param servletContext the {@link ServletContext} to use
-     * @return the configured default {@link WebSocketUpgradeFilter} instance
+     * @param servletContext the {@link ServletContext} to use.
+     * @return the configured default {@link WebSocketUpgradeFilter} instance.
      */
     public static FilterHolder ensureFilter(ServletContext servletContext)
     {
@@ -132,8 +137,6 @@ public static FilterHolder ensureFilter(ServletContext servletContext)
         }
     }
 
-    public static final String MAPPING_ATTRIBUTE_INIT_PARAM = "org.eclipse.jetty.websocket.util.server.internal.WebSocketMapping.key";
-
     private final Configuration.ConfigurationCustomizer defaultCustomizer = new Configuration.ConfigurationCustomizer();
     private WebSocketMapping mapping;
 
@@ -174,10 +177,9 @@ public void init(FilterConfig config) throws ServletException
         final ServletContext context = config.getServletContext();
 
         String mappingKey = config.getInitParameter(MAPPING_ATTRIBUTE_INIT_PARAM);
-        if (mappingKey != null)
-            mapping = WebSocketMapping.ensureMapping(context, mappingKey);
-        else
-            mapping = new WebSocketMapping(WebSocketServerComponents.ensureWebSocketComponents(context));
+        if (mappingKey == null)
+            mappingKey = WebSocketMapping.DEFAULT_KEY;
+        mapping = WebSocketMapping.ensureMapping(context, mappingKey);
 
         String max = config.getInitParameter("idleTimeout");
         if (max == null)

jetty-websocket/websocket-util-server/src/main/java/org/eclipse/jetty/websocket/util/server/internal/WebSocketMapping.java

@@ -63,7 +63,6 @@ public class WebSocketMapping implements Dumpable, LifeCycle.Listener
     public static WebSocketMapping getMapping(ServletContext servletContext, String mappingKey)
     {
         Object mappingObject = servletContext.getAttribute(mappingKey);
-
         if (mappingObject != null)
         {
             if (mappingObject instanceof WebSocketMapping)
@@ -86,7 +85,6 @@ public WebSocketCreator getMapping(PathSpec pathSpec)
     public static WebSocketMapping ensureMapping(ServletContext servletContext, String mappingKey)
     {
         WebSocketMapping mapping = getMapping(servletContext, mappingKey);
-
         if (mapping == null)
         {
             mapping = new WebSocketMapping(WebSocketServerComponents.ensureWebSocketComponents(servletContext));