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This open source software is a reference implementation, consisting of software and related files, for the OMG specification called the Semantics of a Foundational Subset for Executable UML Models (fUML). The reference implementation is intended to implement the execution semantics of UML activity models, accepting an XMI file from a conformant UML model as its input and providing an execution trace of the selected activity model(s) as its output. The core execution engine, which is directly generated from the normative syntactic and semantic models for fUML, may also be used as a library implementation of fUML in other software.

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package org.modeldriven.fuml.io;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.modeldriven.fuml.assembly.ElementAssemblerEventListener;
import org.modeldriven.fuml.assembly.ElementGraphAssembler;
import org.modeldriven.fuml.assembly.ElementStubAssembler;
import org.modeldriven.fuml.xmi.XmiChildFinder;
import org.modeldriven.fuml.xmi.stream.StreamNodeEvent;
import org.modeldriven.fuml.xmi.stream.StreamNodeListener;
import org.modeldriven.fuml.xmi.validation.ErrorCode;
import org.modeldriven.fuml.xmi.validation.ValidationError;
import org.modeldriven.fuml.xmi.validation.ValidationErrorCollector;
import org.modeldriven.fuml.xmi.validation.ValidationEventListener;

public class IncrementalElementReader extends ElementReader 
    implements StreamNodeListener 
{	
    private static Log log = LogFactory.getLog(IncrementalElementReader.class);
    
    private static String STREAM_ELEMENT_NAME_PACKAGED_ELEMENT = "packagedElement";
    
    public IncrementalElementReader() {
    }
    
    public String[] getElementNames()
    {
        return new String[] {
        		STREAM_ELEMENT_NAME_PACKAGED_ELEMENT
        };
    }

    public void nodeCreated(StreamNodeEvent event) {
        // not interested
    }

    public void nodeCompleted(StreamNodeEvent event) {

    	if (log.isDebugEnabled())
    		log.debug("nodeCompleted '" + event.getSource().getLocalName()
    				+ "'");
        XmiChildFinder childFinder = new XmiChildFinder(
                event.getSource().getLocalName());
        event.getSource().accept(childFinder);
        if (childFinder.getResult() != null) {
        	if (log.isDebugEnabled())
        		log.debug("ignoring element '" + event.getSource().getLocalName()
        				+ "' as non-atomic packaged element");
            return; // has a descendant with our local name. We want "atomic" packaged elements
        }    
        // FIXME: make finder namespace aware

        if (!event.getSource().getContext().getUmlNamespace().getNamespaceURI().equals(
                event.getSource().getNamespaceURI()))
            return; // not in UML namespace

        if (log.isDebugEnabled())
            log.debug("validating: "
                + event.getSource().getXmiType() + "("
                + event.getSource().getXmiId() + ")");

        ValidationErrorCollector errorCollector = new ValidationErrorCollector(
                event.getSource());
        errorCollector.setValidateExternalReferences(this.validateExternalReferences);
        if (this.validationEventListeners != null)
        	for (ValidationEventListener listener : this.validationEventListeners)
        		errorCollector.addEventListener(listener);
        errorCollector.validate();

        int count = errorCollector.getErrorCount();
        if (count == 0) // valid
        {
            ElementGraphAssembler assembler =
                new ElementGraphAssembler(event.getSource());
            assembler.setAssembleExternalReferences(this.assembleExternalReferences);
            if (this.elementAssemblerEventListeners != null)
            	for (ElementAssemblerEventListener listener : this.elementAssemblerEventListeners)
            		assembler.addEventListener(listener);
            assembler.start();
            assembler.clear();

            freeNode(event); 
        }
        else
        {
            // For packagedElement, allow internal (and external?) invalid reference errors, as these are to
            // be resolved in a later traversal over the data. For errors other than these
            // we create a stub element such that we can still reference it.
            int internalCount = errorCollector.getErrorCount(ErrorCode.INVALID_REFERENCE);
            if (count > internalCount) // invalid
            {
                if (log.isDebugEnabled())
                    log.debug("found invalid node: "
                        + event.getSource().getXmiType() + " ("
                        + event.getSource().getXmiId() + ")");

                ElementStubAssembler stubAssembler =
                    new ElementStubAssembler(event.getSource());
                if (this.elementAssemblerEventListeners != null)
                	for (ElementAssemblerEventListener listener : this.elementAssemblerEventListeners)
                		stubAssembler.addEventListener(listener);
                stubAssembler.start();
                
                for (ValidationError error : errorCollector.getErrors())
                	stubAssembler.addErrorText(error.getText());

                freeNode(event); 
            }
            else // unresolved references
                if (log.isDebugEnabled())
                    log.debug("found node with unresolved references: "
                        + event.getSource().getXmiType() + " ("
                        + event.getSource().getXmiId() + ") - ignoring during incremental loading");
        }
    }
    
    /**
     * Free (clip) the given XMI sub-graph from the stream, 
	 * so to recoup it's memory and keep processing
     * @param event - the event containing the XMI node to remove
     */
    private void freeNode(StreamNodeEvent event) {
        if (event.getParent() != null)
            if (!event.getParent().removeChild(event.getSource()))
                throw new IOException("could not remove assembled node: "
                    + event.getSource().getXmiType() + " ("
                    + event.getSource().getXmiId() + ")");
    	
    }
}