如何在Eclipse中使用BPMN2 Modeler插件修改和保存BPMN模型？

问：

我想对 BPMN 模型进行更改，并将修改后的模型另存为新模型。我有下面的代码作为演示，它试图删除模型的最后一个元素，但似乎它没有正确完成。打开修改后的模型时，图表信息似乎消失了。我还收到有关序列流未解析引用的错误。我很感激你在这方面的帮助？

    private static void removeLastNode() {
        String modelPath = "process_2.bpmn";
        URI uri = URI.createURI(modelPath); 
        Bpmn2ResourceFactoryImpl resFactory = new Bpmn2ResourceFactoryImpl();
        Resource resource = resFactory.createResource(uri); 
        HashMap<Object, Object> options = new HashMap<Object, Object>();
        options.put(XMLResource.OPTION_DEFER_IDREF_RESOLUTION, true);   
        try {
        // Load the resource
            resource.load(options);
        }
        catch(Exception e){         
        }
        // This is the root element of the XML document
        Definitions d = (Definitions) resource.getContents().get(0).eContents().get(0);
        
        //if more than 1 node in the process, then extract and remove the last node             
        for(RootElement re: d.getRootElements()) {
            if(re instanceof Process) {
                Process p = (Process)re;                    
                FlowElement node_toRemove = null;
                List<SequenceFlow> seqflowList_toRemove = new ArrayList();
                for(FlowElement fe: p.getFlowElements()) {                  
                    if(fe instanceof FlowNode) {
                        FlowNode fn = (FlowNode)fe;
                        if(fn.getOutgoing().size()==0) {//no outgoing node
                            node_toRemove = fe;
                            //get the list of the incoming sequence flows of the element
                            for(SequenceFlow sf: fn.getIncoming()) {
                                seqflowList_toRemove.add(sf);
                            }
                            break;
                        }
                    }                       
                }               
                
                //remove node and its seq flows
                for(SequenceFlow sf: seqflowList_toRemove) {
                    p.getFlowElements().remove(sf);
                }
                p.getFlowElements().remove(node_toRemove);                      
                                
            }
        }
                
        String newFileName = "newModel" + ".bpmn";
        try {           
            File f = new File(newFileName);
            URI new_uri = URI.createURI(f.getPath());   
            resource.setURI(new_uri);
            resource.save(options);
            System.out.println("model " + newFileName + " saved!");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }