Bug 123523 Previewing a scripted data set mapped to a java event handler throws NPE
When previewing a scripted data set we try to get a class loader from the ExecutionContext. (See ScriptExecutor.getClassUsingCustomClassPath). The context will be null in this case. The reason for using the context is to use cached class loaders when possible. Need to use some other mechanism to get the class loader if the context is null. We can either provide an external map to use as cache, or not bother with caching at all.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/script/eventadapter/ScriptedDataSetEventAdapter.java
return false;
	}
	public void close( IDataSetInstance dataSet )
	{
	}
	public void beforeOpen( IDataSetInstance dataSet,
			IReportContext reportContext )
	{
	}
	public void afterOpen( IDataSetInstance dataSet,
			IReportContext reportContext )
	{
	}
	public void onFetch( IDataSetInstance dataSet, IDataSetRow row,
			IReportContext reportContext )
	{
	}
	public void beforeClose( IDataSetInstance dataSet,
			IReportContext reportContext )
	{
	}
	public void afterClose( IReportContext reportContext )
	{
	}
	public boolean describe(IDataSetInstance dataSet, IScriptedDataSetMetaData metaData) 
	{
		return false;
	}
}