What is the difference between using a "Web Service" and calling a server page such as JSP/ASPX?
To me it looks like a Web Service is just a framework around the server pages. For e.g. I can have a JSP page that takes:
mypage.jsp?method=getupdate¶m1=23¶m=44
(I can also send these variables through POST)
In my JSP page I can call the appropriate method based on the value of "method" and return a value back to the caller client app. Is this the raw form how a Web Service actually works? OR is there more to a Web Service call like someone told me that when you call a page, it is rendered but a Web Service is not rendered. But What if I remove the HTML code from JSP page then?
So when we say XML Web Service, the difference is that the client and the server both wrap/unwrap the requests/responses using XML and POST it to the Web Service page.
Web Services are a well defined set of standards defined by the W3C and other relevant bodies, which mostly define an architecture that runs over a network to communicate diverse applications while ensuring interoperability, discoverability and some other relevant criteria.
You can certainly create a server page just for your application without SOAP or XML-RPC. It's just that you shouldn't call it a "Web Service" unless it outputs SOAP or XML-RPC and provides a WSDL description for itself, because that leads to confusion and show you don't know what the "standard Web Services" mean.
You are correct to say that web services are a layer on top of the server pages. One of the common types of web services are SOAP web services that wrap requests and response into XML to achieve interoperability between different platforms/frameworks.
Sites like Facebook and Flickr that have much the same kind of public APIs are calling them 'web services' and I don't see that you're doing anything different.
Vinko seems to have some objection to polluting the 'Web Service' moniker but there's plenty of room under the W3 definition of a web service to include what you're doing.
As for Web services having to output SOAP or XML and provide a WSDL? I think there's a few REST advocates that would argue that point.
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I am new to Web development. And hence, if the question is dumb, please be polite. For creating my application, I had to take a decision of whether writing a web service or a web application. After searching a few questions in stackoverflow, I came to know that, web service is something which doesn't involve human interaction. And web application is what human uses ( the UI/web page kind of stuffs ).
But lately, I saw gmail is a web service ( email service ). But I was confused from here on, because, gmail provides a UI, and human interactions do occur. And from there on, I got confused again.
So what I figured out from this is, gmail website is like a web application for users to use directly. The web application in turn uses the web service provided by Google for email. Is my understanding right? So can a web application be a client for web service?
If I am wrong somewhere, please do correct me. I hope to be clear after someone throws light on this with some good example. Thanks in advance.
You are quite right. Basically a Web Service has several endpoints over HTTP (normally) that provides data (generally in JSON or XML) and are meant to be consumed by Web Clients. Sometimes the are also called Web API's (Application Program Interface).
A Web Application is quite similar to a Web Service but it provides an interface where the user can interact with. Usually Web Applications are consumers of Web Services or Web APIs.
Following your example, Google email is could be considered as both, a Web Service and a Web Application. It is a Web Service because it provides a set of HTTP endpoints that works independently of its Web UI Application (GMail). In fact, you can find third party Web Apps that interact with the Google email Web API.
This concept is very important when designing Web Solutions. Ideally you want to design and implement a good Web API, usually a RESTful Service (in JSON/XML). Then you or others will be able to implement different types of applications (Web, Mobile, etc.) because of this API.
I am not sure if I am comparing onion with a cabbage. But I am really confused with the portlet and a web service. I know that web service is making your software components in your application as a service to other applications but to me it is similar to a portlet responding to requests. I know that my understanding is making you(Portlet & SAAS developers) really upset. But I need some clarity on this.
Why cannot I use the request-response to portlet work similar to a web service?
If yes, what is the benefit I get in using a web service than a portlet?
If not, then what are portlets lacking to act as a web service?
I am a newbie in portlet development. Please dont curse me for this question.
Please suggest.
EDIT:
Most of the answer say that the portlet is a UI component. My customer has requested me to create a webservice in liferay. So is it to make a portlet as a web service? If yes, can you please provide a pointer or some code snippet?
Addressing your 'edit' specifically with regards to Liferay...
Liferay plugin projects can expose web services without too much work.
The Liferay Service Builder actually has facilities so you can create SOAP web services or JSON web services backed by tables in the Liferay database (and that make queries on existing database tables). In the case of JSON web services, the URL scheme generated is not RESTful (unfortunately), but it is well defined. With a bit of work on your part you can impose Liferay's permission system on web service calls as well.
Here's a reasonable starting point in the Liferay Developer's Guide:
See the links on that page to SOAP and JSON services.
Note that a 'portlet' is only one type of Liferay plugin. The web service facility is part of the service layer - which can be used by many plugin types. So there isn't necessarily a portlet involved in creating a web service in Liferay, you can make a web service that has no visual component associated with it.
Portlets are areas you create to add and display content. Portlets can be added to the left and right of the center body area and can contain myriad content ranging from news, events, calendars, RSS feeds, collections, plain text, and more. Also, you can set properties and policies for showing the portlets.
you want to use portlet when
You have content you want to have special focus, like news.
You need to specify the configuration data for an item. - i.e. number of entries to show.
You want to give the content editors a choice about when and where to display content.
You'd like to show it only to some groups or users.
On the other hand, web services:
Enables applications to expose their services
“progammatically”, i.e. the services can be invoked by programs
Enables software running on other computers (could be a desktop, mobile phone, PDA, etc.) to invoke operations exposed by Web applications
if you are trying to identify the main difference portal historically, the portlets have three layers architechture (client, middle tier, backend) this cause two weakness:
Different portal groups have no well established way of sharing services
Different technologies(Java, Perl, CORBA, EJB) in middle tier.
Different protocols(GRAM, IIOP,...)
Consequently, lots of redundancy, reinvention
Example: batch script generation
so Web services address the service sharing problem and reduces the redundancy.
source1 source2 source3
Portlets are meant to be a user interface component in a portal solution.
Web Services provide functionality to remotely interact with a system commonly using SOAP, REST, JMS or other related
They provide completely separate functions. The closest you get is the serveResource method in portlets. This functionality is used to serve various types of content from a portlet (such as a PDF document or an AJAX response) without the need to perform a full page request.
Lets have an example scenario:
Client opens a web site and finds the sum of two numbers which he enters from the textboxes.Then clicks on the ADD button.Two parameters are HTTP GET'ed to server where PHP code is written to add the numbers and result is echo'ed.
Based on this scenario could anybody explain the difference between Web services and application?
In your case if you have User Interface for providing two numbers and then getting the result, it should be called a web application. But if you have an API exposed to receive two numbers and return result over http , then it should be called a web service.
At low level, both Web application and web service are kind of same thing. But the main point is that web services are for machine/program to machine/program communication whereas Web application is for Users.
I'd say that web applications are intended for users and web services are intended for other applications. That's the most important difference. Web applications usually present data in HTML which looks nice to the user and web services usually present data in XML which easy to parse by other applications.
A person drives a car. That car could be powered by an internal combustion engine, electric motor, or nuclear reactor. The power source doesn't matter to the driver though, as all they need to see are the controls and the road ahead.
The application is the car. Web services are the nuclear reactor.
To add 2 no.s we write a web service, to subtract we write a diffrent web service, however calculator is an web application that uses add,subtract and many other webservices in combine.
Lets take an example of Google search.
We can use Google search in two ways. First, we can visit http://www.google.com and put out query for search. Google the returns the result. Second, we can integrate Google Search in our websites with custom search API.
In first case Google Search is acting as web application while in second example it is acting as web service.
Here we can point out few differences,
User interacts with web application while machine interacts with web service.
To access web application, one must visit application. While web service can be access from anywhere (from any application which integrated it). We don't need to visit the service explicitly.
A webservice is equivalent to a method in java that has a web wrapper around it. It lives on the server and it can be sent data / queried etc. and may or may not return a result. It does not have any front end it can only be accessed via http get, put, delete etc.
A web Application is a fully functional piece of software that lives on a sever that is designed to help people achieve a task. This would have a front end that would allow users to interact with it / enter data etc.
A web application could use multiple webservices to achieve its goal / end result
There is little difference between web application and web services.
Web Application: In web application when user request any data then the server embeds the response into some HTML and forward it to the user and on browser the HTML is rendered.
While in web services it's done differently that when some user requests for some data then the server returns it a json or XML array of objects and the data can be displayed by anyway the web designers wants.
Thanks Hope it resolves the matter.
Web service is for application consumption , invoked through web application
To communicate with webservice data should be sent as SOAP message or as REST i.e XML over HTTP
Most of the times web service is not part of application because to facilitate the use by other web applications and it is not for direct consumption to end users
Web application is for human consumption invoked directly by GUI which may or may not use web service for giving response
I am looking for some good starting point for developing web-service.
I have one application which has C++ library support using which I can get all the details of the product.
I am supposed to write web service SDK for the same.
Any help.
Web services generally refer to a technique that allows code to be called via HTTP requests and responses. This is similar to a web page, except that what is returned from a web service is usually not HTML intended to be displayed in a browser - it is usually data of some kind.
"Web Service" is one of those terms that means whatever the person saying it means. Basically, its just a way to access data or functionality via http. There's a few standardized methods - REST, SOAP for web services, or you can just serve up XML, JSON, or other data from a plain old server side web app.
What you'd want to do is investigate what form this Web Server you are supposed to write needs to be in (SOAP, REST, something else), and then go from there.
When I want to find a "Big" Web service (WS-*/WSDL based) of required functionality I can simply google for ".... filetype:wsdl" because Google indexes also WSDL definitions. Or I can simply use some registries that already crawled the Web for WSDL definitions for me, e.g. SeekDa.com or ServiceFinder.
When I want to find RESTful Web service (RESTful Web API) I may count only on the community, because it is not possible to distinguish between URI of RESTful Web service and other Web resources (e.g. Web sites URLs) and hence any focused crawler cannot tell for 100% sure: this is URI of RESTful Web service. So, I come e.g. to the ProgrammableWeb.com and I hope someone already used/found the service I'm looking for and registered it there.
Recently, I was looking for the Web service for abbreviation expansion. I couldn't find it in portals like ProgrammableWeb, because no-one has put it there. Finally I was forced to browse through several abbreviation dictionaries sites, dig and drill there and I finally found Abbreviations.com Web service API in RESTful form. That took me a lot of time!
Is there any other Way to discover RESTful Web services on the Web?
There is a convention (recommended in REST API Design Handbook for example) that you expose a /api endpoint at the root of your service. This returns an XML or JSON response containing the "child" resources that your service supports e.g. /api/products
The REST ideal is that services are as consumable as Web Pages are, they don't need registries. [Got to admit I don't fully "get" the implications of this RESTful world, no WSDL, no registry feels like riding a bike with no stabilisers.]
In the old Web, pre-Google, how did we find pages? Effectively word-of-mouth and a few key starting points. REST services so far as I can see are pretty much in the pre-Google stage.
I don't agree that "it is not possible to distinguish between URI of RESTful Web service and other Web resources" - if we follow the link we get certain types of content application/xml and application/json would be pretty strong indicators wouldn't they?
There's a WSDL-like file for REST webservices: it's called WADL.
SoapUI now can discover the REST services. It works as a proxy, writing down all requests/responses that pass through. Having requests and responses SoapUI recreates descriptions/definitions of the services.
Now the definitions can be stored in WADL and WSDL formats (as WSDL and XML-Schema in XML world). It also can be stored in Swagger format. I prefer Swagger.
Swagger can be stored in SwaggerHub right from SoapUI, which is like GitHub for source code. SwaggerHub is one of many API management systems.