SpotlessCache.java

/*
 * 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.io.IOException;
import java.io.Serializable;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;

/**
 * Spotless' global cache. {@link SpotlessCache#clear()} should be called
 * when Spotless is no longer in use to release any resources it has grabbed.
 */
public final class SpotlessCache {
	/** Allows comparing keys based on their serialization. */
	static final class SerializedKey {
		final byte[] serialized;
		final int hashCode;

		SerializedKey(Serializable key) {
			Objects.requireNonNull(key);
			serialized = LazyForwardingEquality.toBytes(key);
			hashCode = Arrays.hashCode(serialized);
		}

		@Override
		public final boolean equals(Object other) {
			return other instanceof SerializedKey
					&& Arrays.equals(serialized, ((SerializedKey) other).serialized);
		}

		@Override
		public final int hashCode() {
			return hashCode;
		}
	}

	final Map<SerializedKey, URLClassLoader> cache = new HashMap<>();

	@SuppressFBWarnings("DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED")
	synchronized ClassLoader classloader(JarState state) {
		SerializedKey key = new SerializedKey(state);
		return cache
				.computeIfAbsent(key, k -> new URLClassLoader(state.jarUrls(), null));
	}

	static SpotlessCache instance() {
		return instance;
	}

	/** Closes all cached classloaders. */
	public static void clear() {
		List<URLClassLoader> toDelete;
		synchronized (instance) {
			toDelete = new ArrayList<>(instance.cache.values());
			instance.cache.clear();
		}
		for (URLClassLoader classLoader : toDelete) {
			try {
				classLoader.close();
			} catch (IOException e) {
				throw ThrowingEx.asRuntime(e);
			}
		}
	}

	private static final SpotlessCache instance = new SpotlessCache();
}