因为这个项目license问题无法开源，更多技术支持与服务请加入我的知识星球。

1、因为仿钉钉设计器里发送消息处理是一个服务任务，所以要根据这个服务任务进行处理

2、这里目前只对消息进行处理，就是用websocket的发送方式

输入相应的内容，这里也用扩展属性来处理

3、相应的后端代码如下：

public class NotifyNode extends AssigneeNode {
    private List<NotifyTypeEnum> types;
    private String subject;
    private String content;

    @Override
    public List<FlowElement> convert() {
        ArrayList<FlowElement> elements = new ArrayList<>();
        // 服务节点
        ServiceTask serviceTask = new ServiceTask();
        serviceTask.setId(this.getId());
        serviceTask.setName(this.getName());
        serviceTask.setAsynchronous(false);
        serviceTask.setImplementationType(ImplementationType.IMPLEMENTATION_TYPE_CLASS);
        serviceTask.setImplementation("org.jeecg.modules.flowable.ServiceTask.notifyDelegate");
        //增加扩展属性 add by nbacheng
        Map<String, List<ExtensionElement>> extensionElements = new HashMap<String, List<ExtensionElement>>();
        ExtensionElement extensionElementTotal = new ExtensionElement();
        extensionElementTotal.setName("flowable:properties"); 
        
        ExtensionElement eElementUser = new ExtensionElement();
        eElementUser.setName("flowable:property");
        ExtensionAttribute eAttributeUserName = new ExtensionAttribute();
        eAttributeUserName.setName("name");
        eAttributeUserName.setValue("notifyUserList");
        eElementUser.addAttribute(eAttributeUserName);
        ExtensionAttribute eAttributeUserValue = new ExtensionAttribute();
        eAttributeUserValue.setName("value");
        eAttributeUserValue.setValue(StringUtils.join(this.getUsers(), ","));
        eElementUser.addAttribute(eAttributeUserValue);
        extensionElementTotal.addChildElement(eElementUser);
        
        ExtensionElement eElementSubject = new ExtensionElement();
        eElementSubject.setName("flowable:property");
        ExtensionAttribute eAttributeSubjectName = new ExtensionAttribute();
        eAttributeSubjectName.setName("name");
        eAttributeSubjectName.setValue("subject");
        eElementSubject.addAttribute(eAttributeSubjectName);
        ExtensionAttribute eAttributeSubjectValue = new ExtensionAttribute();
        eAttributeSubjectValue.setName("value");
        eAttributeSubjectValue.setValue(this.getSubject());
        eElementSubject.addAttribute(eAttributeSubjectValue);
        extensionElementTotal.addChildElement(eElementSubject);
        
        ExtensionElement eElementContent = new ExtensionElement();
        eElementContent.setName("flowable:property");
        ExtensionAttribute eAttributeContent = new ExtensionAttribute();
        eAttributeContent.setName("name");
        eAttributeContent.setValue("content");
        eElementContent.addAttribute(eAttributeContent);
        ExtensionAttribute eAttributeContentValue = new ExtensionAttribute();
        eAttributeContentValue.setName("value");
        eAttributeContentValue.setValue(this.getContent());
        eElementContent.addAttribute(eAttributeContentValue);
        extensionElementTotal.addChildElement(eElementContent);
        
        extensionElements.put("notifyUserList", CollUtil.newArrayList(extensionElementTotal));
        serviceTask.setExtensionElements(extensionElements);
        elements.add(serviceTask);
        // 下一个节点的连线
        Node child = this.getChild();
        SequenceFlow sequenceFlow = this.buildSequence(child);
        elements.add(sequenceFlow);
        // 下一个节点
        if (Objects.nonNull(child)) {
            child.setBranchId(this.getBranchId());
            List<FlowElement> flowElements = child.convert();
            elements.addAll(flowElements);
        }
        return elements;
    }
}

4、相应的效果图