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Independent Rest API service and Website

I have designed a independent Angular 4 application in Node.js and also design a rest api service using dropwizard. I have tried to connect website as static asset for dropwizard service but I could not integrate it properly. I had gone through several links on google, everywhere repeating same thing which I have tried many a times.
One thing I thought of deploying both of these independently but a question rises how?? How can I deploy two thing on server under same domain?
Another thing which can be possible is Integrate Dropwizard with angular app, which I have tried and read many docs. but still If someone can give some sort of link related to creating these in maven is most welcome.
I need some insight regarding this.
Thanks.

How can I deploy two thing on server under same domain?
Deploy them behind a reverse proxy like nginx and use different context paths.

You could serve the result of package Angular app as a Dropwizard asset
Then you can call the rest API from Angular.
Remember that Dropwizard is just some code to glue together Jersey (for rest), Jetty (webserver) and Jackson (JSON), with the main purpose of simplifying configuration.

spring boot microservice framework how to call another microservice from one microservice

I am trying to build a new application with spring boot microservice framework. I have tried some demo. The existing demo is too simple, doesn't introduce how to call another service from one service. Should still going through http, or should going through RPC? If going RPC, which RPC framework support?

The way of integrating among services depends on numerous factors, like synchronicity/asynchronicity, load that will be generated, etc. The most popular (I guess) way of integration is REST-based one. Because you tagged your question with spring I would recommend using declarative REST client - Feign that is very well described here. You can use message brokers as well, which are also very well abstracted by Spring Cloud Stream - you can read more here. I think that more in depth discussion should be based on your needs.

If another micro-services are exposing the REST API , then you can simple use jersey client
or httpclient to call them.

Two spring boot apps communicating with messaging queue between each other

I have two spring boot apps running in the same local network and they need to communicate with each other. An obvious answer is to leverage REST API and make http calls, but I would like to use Spring Integration project for this purpose.
That said, I have several architectural questions regarding that:
Should I setup a standalone messaging framework (e.g. Rabbit MQ) or embedded should also work (e.g. messaging will be embedded to one of the two apps).
If standalone, what messaging framework should I choose: ActiveMQ, RabbitMQ or something else?

Welcome to the Messaging Microservices world!
You go right way, but forget the embedded middleware if you are going to production. Especially when your application will be distributed geographically.
So, right you need some Message Broker and that should be definitely external one.
It's really your choice which one is better for your purpose. For example you can even take into account Apache Kafka or Redis.
If we talk here about Spring Integration it might be better for you to consider to use our new product - Spring Cloud Stream.
With that you just have your applications as Spring Boot Microservices which are able to connect to the external middleware transparently for the application. You just deal with message channels in the application!

Existing spring application extension by adding camel features

I have my web application written in Spring MVC. It is quite simple app for registering some activities and generating reports after some time. Now I have it done fully in Spring. The only entry point is HTTP webapp request. I'd like to add other entry points to allow user to trigger application via JMS queue, FTP files and SOAP-based web service.
I know I can do this all using Spring own features somehow, but I wonder if it is desirable to involve Apache Camel into all that stuff?
I think about leaving web application as it is (communicating directly with services), only add some Camel magic to spring context and expose several endpoints from Camel and then after messages processing and transformations call existing services.
I think about using Camel to be able to use some asynchronous processing and threads/scalability features. Is it the right way to go?

I will recommend you to use Apache Camel. I have used it for a similar purpose. The solution is an appropriate one from a 'Separation of Concerns' point. Camel implement Enterprise Integration Patters and is a better solution for integrating various protocols and interfaces. Your application should deal with functionality only and as designed should just expose a servlet to get requests and process it.
Handling of interfaces and protocols are well structured in Camel and its easy to maintain and configure in the long run.

Notification Mechanism Using Spring

I have currently two wars files in which one war has to send notification to other war file using spring.Both of the wars are implemented using spring and web service.
My requirement is first war has to send notifications to other war file.
Could you please provide some pointers to implement the same using spring ?

I do not know exactly your requirements but I'd suggest you to use RestFull web service for this notification. Spring has a perfect support of this kind of services.
Internally the first application will send HTTP POST (or GET) request like http://thehost/webapp2/mynotification
Other way is to communicate using JMS. This way is good if you have to make the communication asynchronous. Spring supports JMS using JMS templates.

You can use:
JMS
a webservice (or spring http invoker) in the target app and invoke it from the notifier

You can use RMI to export your beans and make them visible from other modules, better than other alternatives in this case because:
JMS is asynchronous and needs a middleware.
Webservice are less efficient (since it is mostly conceived to communicate heterogeneous platforms).
Take a look here on how to do it:
http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/remoting.html#remoting-rmi
But I would first of all review the architecture you are using, in case you can refactor it for a better integration of business logic.