Replaced "local first" class loading approach by "missing only" appro…

…ach.

lib/src/main/java/com/diffplug/spotless/FeatureClassLoader.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2016 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.spotless;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Objects;
+
+/**
+ * The requests to load a class for a feature is first delegated to the system class loader,
+ * before the feature class loader searches the provided URLs. In case the class resolution or
+ * verification fails, the request is delegated to the class loader of the build tool.
+ * <br/>
+ * Features shall be independent from build tools. Framework capabilities provided by
+ * build tools can be explicitly accessed by omitting the run-time dependencies for these
+ * classes in the provided URLs.
+ * <br/>
+ * For build tools not supporting framework capabilities required by certain features,
+ * the Spotless plugin for the specific build tool provides the missing framework capabilities.
+ */
+public class FeatureClassLoader extends URLClassLoader {
+	static {
+		try {
+			ClassLoader.registerAsParallelCapable();
+		} catch (NoSuchMethodError ignore) {
+			// Not supported on Java 6
+		}
+	}
+
+	private final ClassLoader buildToolClassLoader;
+
+	/**
+	 * Constructs a new FeatureClassLoader for the given URLs, based on an {@code URLClassLoader},
+	 * using the system class loader as parent. In case the class resolution or verification fails,
+	 * the the class loader of the build tool is used.
+	 *
+	 * @param urls the URLs from which to load classes and resources
+	 * @param buildToolClassLoader The build tool class loader
+	 * @exception  SecurityException  If a security manager exists and prevents the creation of a class loader.
+	 * @exception  NullPointerException if {@code urls} is {@code null}.
+	 */
+
+	public FeatureClassLoader(URL[] urls, ClassLoader buildToolClassLoader) {
+		super(urls, null);
+		Objects.requireNonNull(buildToolClassLoader);
+		this.buildToolClassLoader = buildToolClassLoader;
+	}
+
+	@Override
+	protected Class<?> findClass(String name) throws ClassNotFoundException {
+		try {
+			return super.findClass(name);
+		} catch (ClassNotFoundException e) {
+			return buildToolClassLoader.loadClass(name);
+		}
+	}
+
+}

lib/src/main/java/com/diffplug/spotless/JarState.java

@@ -105,10 +105,6 @@ public ClassLoader getClassLoader() {
 		return SpotlessCache.instance().classloader(this);
 	}
 
-	public ClassLoader getClassLoaderOld() {
-		return SpotlessCache.instance().classloaderOld(this);
-	}
-
 	/**
 	 * Returns a classloader containing only the jars in this JarState.
 	 *

lib/src/main/java/com/diffplug/spotless/SpotlessCache.java

@@ -62,18 +62,11 @@ synchronized ClassLoader classloader(JarState state) {
 		return classloader(state, state);
 	}
 
-	@SuppressFBWarnings("DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED")
-	synchronized ClassLoader classloaderOld(JarState state) {
-		SerializedKey serializedKey = new SerializedKey(state);
-		return cache
-				.computeIfAbsent(serializedKey, k -> new URLClassLoader(state.jarUrls(), null));
-	}
-
 	@SuppressFBWarnings("DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED")
 	synchronized ClassLoader classloader(Serializable key, JarState state) {
 		SerializedKey serializedKey = new SerializedKey(key);
 		return cache
-				.computeIfAbsent(serializedKey, k -> new LocalFirstClassLoader(state.jarUrls(), this.getClass().getClassLoader()));
+				.computeIfAbsent(serializedKey, k -> new FeatureClassLoader(state.jarUrls(), this.getClass().getClassLoader()));
 	}
 
 	static SpotlessCache instance() {

lib/src/main/java/com/diffplug/spotless/markdown/FreshMarkStep.java

@@ -81,7 +81,7 @@ FormatterFunc createFormat() throws Exception {
 			Logger logger = Logger.getLogger(FreshMarkStep.class.getName());
 			Consumer<String> loggingStream = logger::warning;
 
-			ClassLoader classLoader = jarState.getClassLoaderOld();
+			ClassLoader classLoader = jarState.getClassLoader();
 
 			// instantiate the formatter and get its format method
 			Class<?> formatterClazz = classLoader.loadClass(FORMATTER_CLASS);