Spring Batch - Parallel Item Writer

Spring Batch - Parallel Item Writer

here's a quick solution i put together for stackoverflow and writing to many itemwriters in parallel

here's the class

package de.incompleteco.spring.batch.item.support;

import java.util.List;

import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.support.CompositeItemWriter;
import org.springframework.core.task.TaskExecutor;
import org.springframework.util.Assert;

import de.incompleteco.spring.domain.SimpleEntity;

public class ParallelCompositeItemWriter extends CompositeItemWriter< SimpleEntity > {

 private List< ItemWriter< ? super SimpleEntity > > delegates;
 
 private TaskExecutor taskExecutor;
 
 @Override
 public void write(final List< ? extends SimpleEntity > item) throws Exception {
  for (final ItemWriter< ? super SimpleEntity > writer : delegates) {
   taskExecutor.execute(new Runnable()  {
    @Override
    public void run() {
     try {
      writer.write(item);
     } catch (Throwable t) {
      rethrow(t);
     } 
    }
    
    private void rethrow(Throwable t) {
     if (t instanceof RuntimeException) {
      throw (RuntimeException) t;
     }
     else if (t instanceof Error) {
      throw (Error) t;
     }
     throw new IllegalStateException(t);
    }  
   });
  }//end for
 }


 public void setTaskExecutor(TaskExecutor taskExecutor) {
  this.taskExecutor = taskExecutor;
 }
 
 @Override
 public void setDelegates(List < ItemWriter < ? super SimpleEntity > > delegates) {
  this.delegates = delegates;
  super.setDelegates(delegates);
 }

 @Override
 public void afterPropertiesSet() throws Exception {
  super.afterPropertiesSet();
  Assert.notNull(taskExecutor,"Task executor needs to be set");
 }
 
}

and here's a sample configuration to run it

 
  
   
    
   
  
 

 
  
 
 
 
  
  
 
 
 
  
   
   
   
    
   
  
  
   
   
   
    
   
    
 
 
 
  
   
  
  
   
    
  
   
    
 
 
 
 

 
     
     
     
     
     
         
             jdbc:h2:mem:a;DB_CLOSE_DELAY=-1
         
     
  
 
 
     
     
     
     
     
         
             jdbc:h2:mem:b;DB_CLOSE_DELAY=-1
         
     
   
 
 
  
 
 
 
  
 
 

 
 
 

 
     
     
 

there's a couple of things to note;
- Bitronix JTA is used to support XA transactions across multiple databases
- the jdbc stuff is pretty rubbish and needs to be done better