| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.tinkerpop.gremlin.server.op; |
| |
| import org.apache.tinkerpop.gremlin.server.OpProcessor; |
| import org.apache.tinkerpop.gremlin.server.Settings; |
| import org.apache.tinkerpop.gremlin.server.op.standard.StandardOpProcessor; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.Map; |
| import java.util.Optional; |
| import java.util.ServiceLoader; |
| |
| /** |
| * Uses {@link ServiceLoader} to load {@link OpProcessor} instances into a cache. |
| * |
| * @author Stephen Mallette (http://stephen.genoprime.com) |
| */ |
| public final class OpLoader { |
| private static final Logger logger = LoggerFactory.getLogger(OpLoader.class); |
| |
| private static final Map<String, OpProcessor> processors = new HashMap<>(); |
| |
| static { |
| ServiceLoader.load(OpProcessor.class).forEach(op -> { |
| final String name = op.getName(); |
| logger.info("Adding the {} OpProcessor.", name.equals(StandardOpProcessor.OP_PROCESSOR_NAME) ? "standard" : name); |
| if (processors.containsKey(name)) |
| throw new RuntimeException(String.format("There is a naming conflict with the %s OpProcessor implementations.", name)); |
| |
| processors.put(name, op); |
| }); |
| } |
| |
| private static volatile boolean initialized = false; |
| |
| /** |
| * Initialize the {@code OpLoader} with server settings. This method should only be called once at startup but is |
| * designed to be idempotent. |
| */ |
| public static synchronized void init(final Settings settings) { |
| if (!initialized) { |
| processors.values().forEach(processor -> processor.init(settings)); |
| initialized = true; |
| } |
| } |
| |
| /** |
| * Gets an {@link OpProcessor} by its name. If it cannot be found an {@link Optional#EMPTY} is returned. |
| */ |
| public static Optional<OpProcessor> getProcessor(final String name) { |
| return Optional.ofNullable(processors.get(name)); |
| } |
| |
| /** |
| * Gets a read-only map of the processors where the key is the {@link OpProcessor} name and the value is the |
| * instance created by {@link ServiceLoader}. |
| */ |
| public static Map<String, OpProcessor> getProcessors() { |
| return Collections.unmodifiableMap(processors); |
| } |
| |
| /** |
| * Reset the processors so that they can be re-initialized with different settings which is useful in testing |
| * scenarios. |
| */ |
| public synchronized static void reset() { |
| initialized = false; |
| } |
| } |