Java tutorial
/** * Copyright 2012 Netflix, Inc. * * 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.netflix.hystrix.contrib.javanica.command; import com.netflix.hystrix.contrib.javanica.exception.FallbackInvocationException; import org.apache.commons.lang3.ArrayUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import javax.annotation.concurrent.ThreadSafe; import java.util.Arrays; /** * Implementation of AbstractHystrixCommand which returns an Object as result. */ @ThreadSafe public class GenericCommand extends AbstractHystrixCommand<Object> { private static final Logger LOGGER = LoggerFactory.getLogger(GenericCommand.class); public GenericCommand(HystrixCommandBuilder builder) { super(builder); } /** * {@inheritDoc} */ @Override protected Object run() throws Exception { LOGGER.debug("execute command: {}", getCommandKey().name()); return process(new Action() { @Override Object execute() { return getCommandAction().execute(getExecutionType()); } }); } /** * The fallback is performed whenever a command execution fails. * Also a fallback method will be invoked within separate command in the case if fallback method was annotated with * HystrixCommand annotation, otherwise current implementation throws RuntimeException and leaves the caller to deal with it * (see {@link super#getFallback()}). * The getFallback() is always processed synchronously. * Since getFallback() can throw only runtime exceptions thus any exceptions are thrown within getFallback() method * are wrapped in {@link FallbackInvocationException}. * A caller gets {@link com.netflix.hystrix.exception.HystrixRuntimeException} * and should call getCause to get original exception that was thrown in getFallback(). * * @return result of invocation of fallback method or RuntimeException */ @Override protected Object getFallback() { if (getFallbackAction() != null) { final CommandAction commandAction = getFallbackAction(); try { return process(new Action() { @Override Object execute() { Object[] args = commandAction.getMetaHolder().getArgs(); if (commandAction.getMetaHolder().isExtendedFallback()) { if (commandAction.getMetaHolder().isExtendedParentFallback()) { args[args.length - 1] = getFailedExecutionException(); } else { args = Arrays.copyOf(args, args.length + 1); args[args.length - 1] = getFailedExecutionException(); } } else { if (commandAction.getMetaHolder().isExtendedParentFallback()) { args = ArrayUtils.remove(args, args.length - 1); } } return commandAction .executeWithArgs(commandAction.getMetaHolder().getFallbackExecutionType(), args); } }); } catch (Throwable e) { LOGGER.error(FallbackErrorMessageBuilder.create().append(commandAction, e).build()); throw new FallbackInvocationException(e.getCause()); } } else { return super.getFallback(); } } }