From a1e837530eecaee9e3abe1f780eca72721df6d14 Mon Sep 17 00:00:00 2001
From: gregw <gregw@webtide.com>
Date: Wed, 28 Oct 2020 15:42:36 +0100
Subject: [PATCH] Fixes #5521 ResourceCollection NPE

Fix constructor and addPath so that all resources in a RC must exist when created.
---
 .../util/resource/ResourceCollection.java     | 47 ++++++++++---------
 .../util/resource/ResourceCollectionTest.java |  3 +-
 2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/ResourceCollection.java b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/ResourceCollection.java
index 4b7484081f1d..f67232b1ab0f 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/resource/ResourceCollection.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/resource/ResourceCollection.java
@@ -62,8 +62,19 @@ public ResourceCollection()
      * @param resources the resources to be added to collection
      */
     public ResourceCollection(Resource... resources)
+    {
+        this(Arrays.asList(resources));
+    }
+
+    /**
+     * Instantiates a new resource collection.
+     *
+     * @param resources the resources to be added to collection
+     */
+    public ResourceCollection(Collection<Resource> resources)
     {
         _resources = new ArrayList<>();
+
         for (Resource r : resources)
         {
             if (r == null)
@@ -82,17 +93,6 @@ public ResourceCollection(Resource... resources)
         }
     }
 
-    /**
-     * Instantiates a new resource collection.
-     *
-     * @param resources the resources to be added to collection
-     */
-    public ResourceCollection(Collection<Resource> resources)
-    {
-        _resources = new ArrayList<>();
-        _resources.addAll(resources);
-    }
-
     /**
      * Instantiates a new resource collection.
      *
@@ -247,27 +247,28 @@ public Resource addPath(String path) throws IOException
         ArrayList<Resource> resources = null;
 
         // Attempt a simple (single) Resource lookup that exists
+        Resource addedResource = null;
         for (Resource res : _resources)
         {
-            Resource r = res.addPath(path);
-            if (!r.isDirectory() && r.exists())
-            {
-                // Return simple (non-directory) Resource
-                return r;
-            }
-
+            addedResource = res.addPath(path);
+            if (!addedResource.exists())
+                continue;
+            if (!addedResource.isDirectory())
+                return addedResource; // Return simple (non-directory) Resource
             if (resources == null)
-            {
                 resources = new ArrayList<>();
-            }
+            resources.add(addedResource);
+        }
 
-            resources.add(r);
+        if (resources == null)
+        {
+            if (addedResource != null)
+                return addedResource; // This will not exist
+            return EmptyResource.INSTANCE;
         }
 
         if (resources.size() == 1)
-        {
             return resources.get(0);
-        }
 
         return new ResourceCollection(resources);
     }
diff --git a/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceCollectionTest.java b/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceCollectionTest.java
index fc39c573f476..cb5313fe8d0e 100644
--- a/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceCollectionTest.java
+++ b/jetty-util/src/test/java/org/eclipse/jetty/util/resource/ResourceCollectionTest.java
@@ -35,7 +35,6 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.contains;
-import static org.hamcrest.Matchers.emptyArray;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.nullValue;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -189,7 +188,7 @@ public void testList() throws Exception
 
         assertThat(Arrays.asList(rc1.list()), contains("1.txt", "2.txt", "3.txt", "dir/"));
         assertThat(Arrays.asList(rc1.addPath("dir").list()), contains("1.txt", "2.txt", "3.txt"));
-        assertThat(rc1.addPath("unknown").list(), emptyArray());
+        assertThat(rc1.addPath("unknown").list(), nullValue());
     }
 
     @Test