Issue #5133 - Reworking WebAppContext.extraClasspath

+ Reverting name ResourceFactory.newResource(String)
  to .getResource(String)
+ Reintroducing Resource.getResource(String)
+ ResourceHandler.getResource(String) cleaned up
  in light of Exception handling requirement
+ Resource.addPath(String) implementations can
  never return null now

Signed-off-by: Joakim Erdfelt <joakim.erdfelt@gmail.com>

jetty-server/src/main/java/org/eclipse/jetty/server/handler/ResourceHandler.java

@@ -152,18 +152,9 @@ public class ResourceHandler extends HandlerWrapper implements ResourceFactory,
     public Resource getResource(String path) throws IOException
     {
         if (LOG.isDebugEnabled())
-            LOG.debug("{} newResource({}): baseResource:{}", _context == null ? _baseResource : _context, path, _baseResource);
+            LOG.debug("{} getResource({}): baseResource:{}", _context == null ? _baseResource : _context, path, _baseResource);
 
-        if (path == null)
-        {
-            throw new IOException("null path");
-        }
-        else if (!path.startsWith("/"))
-        {
-            throw new IOException("Invalid path reference: " + path);
-        }
-
-        try
+        if (path != null && path.startsWith("/"))
         {
             Resource r = null;
 
@@ -172,15 +163,19 @@ public class ResourceHandler extends HandlerWrapper implements ResourceFactory,
                 path = URIUtil.canonicalPath(path);
                 r = _baseResource.addPath(path);
 
-                if (r != null && r.isAlias() && (_context == null || !_context.checkAlias(path, r)))
+                if (r.isAlias() && (_context == null || !_context.checkAlias(path, r)))
                 {
                     if (LOG.isDebugEnabled())
-                        LOG.debug("resource={} alias={}", r, r.getAlias());
-                    throw new IOException("Unacceptable alias reference: " + r);
+                        LOG.debug("Rejected alias resource={} alias={}", r, r.getAlias());
+                    throw new IOException("Rejected (see debug logs)");
                 }
             }
             else if (_context != null)
+            {
                 r = _context.getResource(path);
+                if (r != null)
+                    return r;
+            }
 
             if ((r == null || !r.exists()) && path.endsWith("/jetty-dir.css"))
                 r = getStylesheet();
@@ -188,10 +183,6 @@ public class ResourceHandler extends HandlerWrapper implements ResourceFactory,
             if (r != null)
                 return r;
         }
-        catch (Exception e)
-        {
-            LOG.debug("Unable to get Resource for {}", path, e);
-        }
 
         throw new IOException("Unable to find Resource for " + path);
     }

jetty-util/src/main/java/org/eclipse/jetty/util/resource/EmptyResource.java

@@ -124,6 +124,6 @@ public class EmptyResource extends Resource
     @Override
     public Resource addPath(String path) throws IOException, MalformedURLException
     {
-        return null;
+        return this;
     }
 }

jetty-util/src/main/java/org/eclipse/jetty/util/resource/Resource.java

@@ -413,7 +413,7 @@ public abstract class Resource implements ResourceFactory, Closeable
      * given name.
      *
      * @param path The path segment to add, which is not encoded
-     * @return the Resource for the resolved path within this Resource.
+     * @return the Resource for the resolved path within this Resource, never null
      * @throws IOException if unable to resolve the path
      * @throws MalformedURLException if the resolution of the path fails because the input path parameter is malformed.
      */

jetty-util/src/main/java/org/eclipse/jetty/util/resource/ResourceCollection.java

@@ -222,7 +222,7 @@ public class ResourceCollection extends Resource
 
         if (path == null)
         {
-            throw new MalformedURLException();
+            throw new MalformedURLException("null path");
         }
 
         if (path.length() == 0 || URIUtil.SLASH.equals(path))
@@ -270,11 +270,13 @@ public class ResourceCollection extends Resource
         {
             return resource;
         }
+
         if (resources != null)
         {
             return new ResourceCollection(resources.toArray(new Resource[0]));
         }
-        return null;
+
+        throw new MalformedURLException("path does not result in Resource: " + path);
     }
 
     @Override

jetty-util/src/main/java/org/eclipse/jetty/util/resource/URLResource.java

@@ -290,7 +290,9 @@ public class URLResource extends Resource
         throws IOException, MalformedURLException
     {
         if (path == null)
-            return null;
+        {
+            throw new MalformedURLException("null path");
+        }
 
         path = URIUtil.canonicalPath(path);
 

jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppClassLoader.java

@@ -88,7 +88,6 @@ public class WebAppClassLoader extends URLClassLoader implements ClassVisibility
      */
     public interface Context extends ClassVisibilityChecker
     {
-
         /**
          * Convert a URL or path to a Resource.
          * The default implementation