{{tag>Programmers_Reference Example Custom_Process}}
[<10>]
==== Examples of custom process components ====

The following example shows the code for the simple process component that changes the attribute of the process input.

<code java>public class SimpleProcess implements IProcess
{
    public SimpleProcess()
    {
    }
    /**
     * @see com.bas.basserver.executionengine.IProcess#cancel()
     */
    @Override
    public boolean cancel()
    {
        return true;
    }
    /**
     * @see com.bas.basserver.executionengine.IProcess#execute(com.bas.basserver.executionengine.IExecutionEngine,java.lang.Object[])
     */
    @Override
    public Object execute(IExecutionEngine engine, Object[] parameters)
    throws SuspendProcessException, ExecutionException, AccessDeniedException
    {
        // one entity is declared as process input
        if (parameters== null || parameters.length!=1 || !(parameters[0] instanceof IEntity))
        {
            return null;
        }
        // get the parameter
        IEntityentity=(IEntity)parameters[0];
        Object oldValue = null;
        try
        {
            // change "attrName" attribute to "attrValue" in memory
            oldValue = entity.getAttributeValue ("attrName");
            entity.setAttributeValue("attrName","attrValue");
        }
        catch (Exception e)
        {   
        }
        try
        {
        // update entity in persistence
            engine.updateEntity(this, entity,
                new String[]{"attrName"}, 
                new Object [] {oldValue} );
        }
        catch (ServerTimeOutExceptionste)
        {
            throw new SuspendProcessException(ste);
        }
        return null;
    }
    /**
     * @see com.bas.basserver.executionengine.IProcess#resume(com.bas.basserver.executionengine.IExecutionEngine,java.lang.Object)
     */
    @Override
    public Objectresume(IExecutionEngineengine,Objectreply)
    throws SuspendProcessException, ExecutionException, AccessDeniedException
    {
        return null;
    }
}
</code>

The next example shows the code of the process that performs some lengthy calculation and throws SuspendProcessException every now and again:

<code java>public class LongProcess implements IProcess
{
    private boolean m_cancelled = false;
    private long m_count;
    public LongProcess()
    {
    }
    /** @see IProcess#cancel()*/
    @Override
    public boolean cancel()
    {
        // set m_cancelled flag. This flag will be checked by execute // and resume methods
        synchronized (this)
        {
            m_cancelled = true;
        }
        return true;
    }
    /**
     * @see IProcess#execute(IExecutionEngine, Object[])
     */
    @Override
    public Object execute(IExecutionEngine engine, Object[] parameters)
    throws SuspendProcessException, ExecutionException
    {
        m_count=0;
        execute(engine);
        return null;
    }
    private void execute(IExecutionEngine engine)
    throws SuspendProcessException
    {
        try
        {
            // get the context in which the process is running
            IExecutionContextmyContext = engine.getExecutionContext(this);
            while (true)
            {
                Thread.sleep(500);
                // finish after 400 iterations
                if (m_count++ >=400)
                    break;
                    // every 4 iterations update our progress
                if (m_count % 4==0)
                {
                    int progress = myContext.getProgress ();
                    if (progress<100)
                        myContext.setProgress (progress + 1);
                }
                // check if we have been cancelled
                synchronized (this)
                {
                    if (m_cancelled)
                        break;
                }
                // every 120 iterations suspend ourselves so that
                // transaction can be committed (though this is 
                // only for illustrational purposes as we are not 
                // doing any transactional operations here such as 
                // changing values of attributes etc)
                if (m_count % 120 == 0)
                {
                    throw new SuspendProcessException (true);
                    // we will be called soon – see resume
                }
            }
        }
        catch (InterruptedException ie)
        {            
        }
    }
    /**
     * @see IProcess#resume(IExecutionEngine,Object)
     */
    @Override
    public Object resume (IExecutionEngine engine, Object reply)
    throws SuspendProcessException, ExecutionException
    {
        // this is called every 120 iterations
        execute (engine);
        return null;
    }
}
</code>

{{simplenavi>:docs:3500:3000:0314:}}