/*
    * Copyright 2006-2008 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.step.job;
  
  import org.springframework.batch.core.Job;
  import org.springframework.batch.core.JobExecution;
  import org.springframework.batch.core.JobParameters;
  import org.springframework.batch.core.Step;
  import org.springframework.batch.core.StepExecution;
  import org.springframework.batch.core.UnexpectedJobExecutionException;
  import org.springframework.batch.core.launch.JobLauncher;
  import org.springframework.batch.core.step.AbstractStep;
  import org.springframework.batch.item.ExecutionContext;
  import org.springframework.util.Assert;
  
  /**
   * A {@link Step} that delegates to a {@link Job} to do its work. This is a
   * great tool for managing dependencies between jobs, and also to modularise
   * complex step logic into something that is testable in isolation. The job is
   * executed with parameters that can be extracted from the step execution, hence
   * this step can also be usefully used as the worker in a parallel or
   * partitioned execution.
   * 
   * @author Dave Syer
   * 
   */
  public class JobStep extends AbstractStep {
  
  	/**
  	 * The key for the job parameters in the step execution context. Needed for
  	 * restarts.
  	 */
  	private static final String JOB_PARAMETERS_KEY = JobStep.class.getName() + ".JOB_PARAMETERS";
  
  	private Job job;
  
  	private JobLauncher jobLauncher;
  
  	private JobParametersExtractor jobParametersExtractor = new DefaultJobParametersExtractor();
  
  	@Override
  	public void afterPropertiesSet() throws Exception {
  		super.afterPropertiesSet();
  		Assert.state(jobLauncher != null, "A JobLauncher must be provided");
  		Assert.state(job != null, "A Job must be provided");
  	}
  
  	/**
  	 * The {@link Job} to delegate to in this step.
  	 * 
  	 * @param job a {@link Job}
  	 */
  	public void setJob(Job job) {
  		this.job = job;
  	}
  
  	/**
  	 * A {@link JobLauncher} is required to be able to run the enclosed
  	 * {@link Job}.
  	 * 
  	 * @param jobLauncher the {@link JobLauncher} to set
  	 */
  	public void setJobLauncher(JobLauncher jobLauncher) {
  		this.jobLauncher = jobLauncher;
  	}
  
  	/**
  	 * The {@link JobParametersExtractor} is used to extract
  	 * {@link JobParametersExtractor} from the {@link StepExecution} to run the
  	 * {@link Job}. By default an instance will be provided that simply copies
  	 * the {@link JobParameters} from the parent job.
  	 * 
  	 * @param jobParametersExtractor the {@link JobParametersExtractor} to set
  	 */
  	public void setJobParametersExtractor(JobParametersExtractor jobParametersExtractor) {
  		this.jobParametersExtractor = jobParametersExtractor;
  	}
  
  	/**
  	 * Execute the job provided by delegating to the {@link JobLauncher} to
  	 * prevent duplicate executions. The job parameters will be generated by the
  	 * {@link JobParametersExtractor} provided (if any), otherwise empty. On a
  	 * restart, the job parameters will be the same as the last (failed)
  	 * execution.
  	 * 
  	 * @see AbstractStep#doExecute(StepExecution)
 	 */
 	@Override
 	protected void doExecute(StepExecution stepExecution) throws Exception {
 
 		ExecutionContext executionContext = stepExecution.getExecutionContext();
 
 		JobParameters jobParameters;
 		if (executionContext.containsKey(JOB_PARAMETERS_KEY)) {
 			jobParameters = (JobParameters) executionContext.get(JOB_PARAMETERS_KEY);
 		}
 		else {
 			jobParameters = jobParametersExtractor.getJobParameters(job, stepExecution);
 			executionContext.put(JOB_PARAMETERS_KEY, jobParameters);
 		}
 
 		JobExecution jobExecution = jobLauncher.run(job, jobParameters);
 		if (jobExecution.getStatus().isUnsuccessful()) {
 			// AbstractStep will take care of the step execution status
 			throw new UnexpectedJobExecutionException("Step failure: the delegate Job failed in JobStep.");
 		}
 
 	}
 
 }