[FIXED JENKINS-44898] Add findResource to PluginFirstClassLoader

core/src/main/java/hudson/PluginFirstClassLoader.java

@@ -27,13 +27,16 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.lang.reflect.Field;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Enumeration;
 import java.util.List;
+import java.util.Vector;
 
 import org.apache.tools.ant.AntClassLoader;
+import org.apache.tools.ant.Project;
 
 /**
  * classLoader which use first /WEB-INF/lib/*.jar and /WEB-INF/classes before core classLoader
@@ -45,7 +48,21 @@ public class PluginFirstClassLoader
     extends AntClassLoader
     implements Closeable
 {
-
+
+    private final Vector pathComponents;
+
+    public PluginFirstClassLoader() {
+        super();
+
+        try {
+            Field $pathComponents = AntClassLoader.class.getDeclaredField("pathComponents");
+            $pathComponents.setAccessible(true);
+            pathComponents = (Vector)$pathComponents.get(this);
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+            throw new Error(e);
+        }
+    }
+
     private List<URL> urls = new ArrayList<URL>();
 
     public void addPathFiles( Collection<File> paths )
@@ -100,6 +117,27 @@ public InputStream getResourceAsStream( String name )
     {
         InputStream is = super.getResourceAsStream( name );
         return is;
-    }   
-
+    }
+
+    /**
+     * As of 1.8.0, {@link AntClassLoader} doesn't implement {@link #findResource(String)}
+     * in any meaningful way, which breaks fast lookup. Implement it properly.
+     */
+    @Override
+    protected URL findResource(String name) {
+        URL url = null;
+
+        // try and load from this loader if the parent either didn't find
+        // it or wasn't consulted.
+        Enumeration e = pathComponents.elements();
+        while (e.hasMoreElements() && url == null) {
+            File pathComponent = (File) e.nextElement();
+            url = getResourceURL(pathComponent, name);
+            if (url != null) {
+                log("Resource " + name + " loaded from ant loader", Project.MSG_DEBUG);
+            }
+        }
+
+        return url;
+    }
 }