/*
 * Copyright 2013 the original author or authors.
 *
 * 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 org.springframework.batch.core.scope.context;

import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.jsr.configuration.support.BatchPropertyContext;

/**
 * Central convenience class for framework use in managing the job scope
 * context. Generally only to be used by implementations of {@link Job}. N.B.
 * it is the responsibility of every {@link Job} implementation to ensure that
 * a {@link JobContext} is available on every thread that might be involved in
 * a job execution, including worker threads from a pool.
 *
 * @author Dave Syer
 * @author Jimmy Praet
 * @since 3.0
 */
public class JobSynchronizationManager {

	private static final SynchronizationManagerSupport<JobExecution, JobContext> manager = new SynchronizationManagerSupport<JobExecution, JobContext>() {

		@Override
		protected JobContext createNewContext(JobExecution execution, BatchPropertyContext args) {
			return new JobContext(execution);
		}

		@Override
		protected void close(JobContext context) {
			context.close();
		}
	};

	/**
	 * Getter for the current context if there is one, otherwise returns null.
	 *
	 * @return the current {@link JobContext} or null if there is none (if one
	 * has not been registered for this thread).
	 */
	public static JobContext getContext() {
		return manager.getContext();
	}

	/**
	 * Register a context with the current thread - always put a matching
	 * {@link #close()} call in a finally block to ensure that the correct
	 * context is available in the enclosing block.
	 *
	 * @param JobExecution the step context to register
	 * @return a new {@link JobContext} or the current one if it has the same
	 * {@link JobExecution}
	 */
	public static JobContext register(JobExecution JobExecution) {
		return manager.register(JobExecution);
	}

	/**
	 * Method for unregistering the current context - should always and only be
	 * used by in conjunction with a matching {@link #register(JobExecution)}
	 * to ensure that {@link #getContext()} always returns the correct value.
	 * Does not call {@link JobContext#close()} - that is left up to the caller
	 * because he has a reference to the context (having registered it) and only
	 * he has knowledge of when the step actually ended.
	 */
	public static void close() {
		manager.close();
	}

	/**
	 * A convenient "deep" close operation. Call this instead of
	 * {@link #close()} if the step execution for the current context is ending.
	 * Delegates to {@link JobContext#close()} and then ensures that
	 * {@link #close()} is also called in a finally block.
	 */
	public static void release() {
		manager.release();
	}
}