The client connects to a server and then can request it AND the server can invoke some commands on the clients as well.
Is there anything like this in Java?
In my opinion there is no such thing called duplex webservices, To achieve Client-Server relationship in both direction (duplex as you termed it), You can expose webservice interface at both the ends for consuming.
Both webservices component acts as Client and Server simultaneously, by exposing consumable web service interface for each other.
See below image for better clarity.
Related
So I have currently been assigned to read about Web Services. I was going through the differences between REST, XML-RPC and SOAP and came across this particular link :
REST vs XML-RPC vs SOAP
It mentions this following, in terms of authentication and authorization
As for authentication and authorization, SOAP places the burden in the hands of the application developer. The REST methodology instead takes into account the fact that Web servers already have support for these tasks. Through the use of industry-standard certificates and a common identity management system, such as an LDAP server, developers can make the network layer do all the heavy lifting.
I was not able to understand this particular reference. Can some one explain how this happens in detail?
A web service is method or mechanism to communicate between different applications using open standard such as XML, WSDL, and SOAP. Using web service different device or program communicates over network
Type of WebService
SOAP Web Service
RESTFul Web Service
more information you can check :http://entityclass.in/rest/home.htm
I am developing an Emergency Response System. I have developed my server using the Django Framework in Python. I have an Android Client which needs to communicate with the Server. My question is :
1) Should I use REST API for communicating between the Android App and the Django Server?
2) Or is there any other RPC methods (like RMI in Java) which should be used for communication?
3) The Client developed as an Android App needs to send requests/messages to the server based on the user interaction. Would a REST API be a good option?
Thanks.
Use HTTP. This is the easiest protocol available to you.
REST is an architecture pattern (it describes how you would design your API service and client). It is designed to use HTTP (a protocol).
In order to implement RMI you would have to find an implementation for JRMP on Android and then make sure that all your users have access to this over the network; you would also have to use TCP/IP which would be near impossible to implement separately on your remote clients (unless you have deep level control over them) and even then, the network should allow such access which most mobile providers will not.
It is not practical, and it will not work reliably.
What does a Web service really mean ? I am not looking for a theoretical explanation, I am looking for something practical.
I was thinking that anything I can call from an external client is a Web service, so a basic PHP which returns JSON data could be a Web service.
But then I started reading about Web services in W3Schools.org and I got confused. If the PHP URL which returns JSON data is a web service, why would I need to do SOAP, WDSL etc ... to create a Web service. Isn't it extra work?
Also, if SOAP is the way data is sent back and forth, what about other transport types?
What differentiates a RESTful Web service from a SOAP based web service?
When you are talking about a webservice people generally misunderstand what it means, a webservice is simply a way to interact between a and b that abstracts the use of local technology standards. A WSDL defines the way in which the SOAP message is being sent over the channel. REST uses JSON over HTTP, WSDL uses SOAP over HTTP.
The advantage of a webservice is, say you develop one piece of code in .net and you wish to use JAVA to consume this code. You can interact directly with the abstracted layer and are unaware of what technology was used to develop the code.
SOA is a set of design paradigms and standards that tell you how to develop your services, in SOA each service is meant to comply with the principles listed below. WSDL is generally linked with but not essential for a SOA solution. If you wish to learn about SOA google "Thomas Erl SOA".
Priciples of SOA
Standardized service contract
Service loose coupling
Service abstraction
Service reusability
Service autonomy
Service statelessness
Service discoverability
Service composability
This Q&A Restful vs Other Web Services brings a lot of light to what is a webserver, and differences from SOAP and REST. Id recommend to read all the answers (many of them are very good).
Does web api have more advantage than socket communication when I am writing a software need calling server to function?
If we write a web api,do we can take advantage of http, http server, web app framework to do more thing with less work than doing the same function by socket ?
If my client call my server through internet, Do we have not any reason to not implement it as web api ?
I'd say that 'web API' is-kind-of a 'socket API'. While socket API may be basically anything running over sockets, web API is done using the HTTP protocol. That has a bit of limitation but usually the advantages are more important:
You reuse existing protocols and methods instead of re-inventing your own ones. That makes the work easier for you, and much easier for your users who do not have to implement everything from scratch;
You can use existing tools (and even a regular web browser) to debug your API. Well, with socket API you usually can use telnet but with more complex cases, a web browser or any HTTP querying tool is simpler to use;
You reuse HTTP ports 80 (and/or 443). That usually means it's less likely that any firewall will forbid your users to access the ports used by your service;
And after all, if you choose the right technologies, you can reuse them 'in' or even 'as' web pages. For example, you can use AJAX or similar technologies to catch data from your API in scripts on your web page.
Even better, if you just use XML for the API output, you can basically make it an API and a web page at the same time. You simply add a reference to an XSLT stylesheet to it, and whenever a web browser uses that API, it will use it to transform the raw XML into HTML.
Web services only output XML instead of HTML. The reasons why you should create a web service does not differs from the ones for creating a web site.
A web API can be called remotely.
A web API can be called in an independant manner. That means that you can allow you user (and you) to use an other interface that the one you build for the final customer.
You can program the API the way you want. The only requirment is to produce valid XML. So, yes you can use some framework, you are supposed to use a web server as the ones that output webpages.
If the client call your service throught Internet (SAAS), creating a web service allow you to give a new interface. Web services are required in order to use SOAP and to allow refreshing of webpages and also to give the datas to a heavy client.
Assume there are 2 web services A and B setup in SOA infrastructure.
Web services A depends on information that is available from the locally installed Desktop application (its a legacy application based on C++ programming and provides C++ API to give the information needed by web service A).
The scenario is this: Human actor (which can be considered as Consumer of web service B)logs into a website and clicks a button which requests the service provided by web service B. As part of this request, his ID is sent. Web service B sends request to web service A with this ID. Web service A uses this ID to somehow determine a way to talk to locally installed desktop application of the human actor who originated the request.
The main problem how can web service A connect to desktop application and get the information in a reliable way using SOA infrastructure.
Assume that everything in this SOA is Java based except the desktop application.
The desktop application is basically like a CRM application with its own internal database and not traditional database like MySQL. It provides just basic textual information about the human actor and about the customer(s) of that human actor in his installed CRM desktop application.
I do want to use SOA related technologies even though it may be more complicated.
Given above details:
How can I use JMS to solve this problem?
If JMS is not the right solution, what about ESB and how can I use ESB to solve this problem?
The communication with the desktop application will greatly be determined by what different methods the application is capable of performing. If the application has a database backend, an ESB can facilitate communication with predefined adapters for the specific database being used. If the application has an api that can be tapped programmatically, that is a method as well. I am not sure JMS would be the appropriate solution since given your use case you would want a synchronous reply. Putting JMS in the middle (somehow) will break that reply and rather return an asynchronous response.
I would recommend looking more into the functionality available in the desktop application and with your findings start with evaluating ESB functionality. An ESB may be overkill for this use case but if you plan to do more operations like this it may become valuable.
I think the problem boils down to a Java Web Service A, having a requirement to talk to a C++ desktop application to get user details.
If the Desktop application is able to use JMS using Stomp etc, ActiveMQ or HornetQ maybe used. This also allows you to scale A into multiple instances across many machines, and use JMS to request user information from the Desktop application.
Another option is to expose a simple API (REST, TCP etc) on the Desktop application and make the Web Service A talk to the Desktop application using that. Again, you could distribute the A into multiple instances for scalability.
You can use an ESB to convert a REST call to TCP, or a SOAP to JMS etc. Basically any-to-any conversion. The Free and Open Source ESB UltraESB [http://adroitlogic.org] contains many examples, and is lightweight (~35MB) so the 'overkill' will be minimal compared to > 300MB+ resource hungry ESBs