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--- docs:3500:0300:0314 [2023/04/05 05:57] – removed - external edit (Unknown date) 127.0.0.1
+++ docs:3500:0300:0314 [2023/04/05 07:40] (current) – [Examples of custom process components] sean
@@ Line 1: / Line 1: @@
+{{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:}}