I am planning to build an application bundle that includes a mobile app, a website and an web service for other developers. Website has the first priority and mobil application has second.
For creating the mobile application ordinarily first i need to create the web service.
What is the way i should follow:
Create web service, than website and mobile application using it.
Create website, than create service and mobile application.
P.S: I will develop the service and website using Scala and Play! Framework
The optimal order will vary depending on priorities and how stable requirements are.
Usually during development, the understanding of the problem improves and the requirements change. This can happen particularly for the user interface. The first usability tests can lead to changes in the application's design and behavior.
A construction order that takes this into account would be:
Create an initial version of the website. Depending on the project this would include a short description of the project, a way to collect emails, and authentication features such as user registration and login.
Create the mobile application, mocking the service layer in the mobile application itself (i.e. using mock service proxy objects). The objective is to discover and stabilize user interface requirements. This process will clarify which services are needed, which operations these services must perform, and exactly which data these operations must receive and provide.
Implement the web service, based on the already stabilized requirements.
Complete the web site, including description of the application's features and benefits, and showing the application's content (e.g. screenshots, videos).
This order assumes the application's features are the main benefit of the project. If, on the other hand, the main value and complexity resides in the web service, and the application is just a thin, optional front-end over it, then it might be more appropriate to develop the web services first and then the application.
I'm going to integrate a Moodle-based application into my website wherein all data/activities being posted in this Moodle-based application can be retrieved by my website and vice versa.
So, is the Moodle web service enough to access all the data in that Moodle application?
Yes, you should be able to use web services. No, not all data is accessible out-of-the-box.
Things you can do with the webservices:
Retrieve a list of users, courses, assignments
Upload files
Create notes
Send messages
Enrol to courses, groups, cohorts
Check grades
On your Moodle site turn on web services and go to /admin/webservice/documentation.php to get a full list of existing functions you can call.
You can see some examples of this implemented in the Moodle Mobile App:
User: http://docs.moodle.org/26/en/Mobile_app
Dev: http://docs.moodle.org/dev/Moodle_Mobile
If these satisfy your requirements then yes web services should be sufficient as they are.
If they do not then you can extend the web services as a local plugin to provide richer functionality, which would be limited by your development capacity rather than the system itself. To port all of the features of some modules to web services would be a significant undertaking, but there are some low-hanging fruit to get activity lists, forum discussions/posts, choice polls, etc.
Web services is a better approach than exposing the database to an external system as it allows you to utilise the core APIs to improve integrity.
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.
I am newbie here and confused by few things
Some websites (twitter, foursquare, etc) provide API to third-party developer to call. are those APIs the web services that the sites provide?
Are those web sites themselves built on top of those public APIs/web services? theoretically is it possible?
Comparing the traditionally built website and the websites build on top of web service, pros and cons? are there any performance, scalability, etc differences?
Thanks in advance!
I'm sure somebody can give you a more exact answer but reading your question and applying my self-taught knowledge:
The simple technical definition of Web Services according to W3C:
A Web service is a software system designed to support interoperable machine-to-machine interaction over a network.
http://www.w3.org/TR/2004/NOTE-ws-gloss-20040211/
I like to think of web services as the interactive elements of a site that its customer base utilizes. For example, Twitter's web services include: tweeting, messages, hashtags, etc. Web services are what users get to DO or DATA passed back and forth.
A public web API provides means for developers to utilize the web services on their own site. For example, Twitter's API allows example.com site to utilize tweeting, messaging, hashtags, etc from within their own domain. An API is how developers get external access to web services to make apps using those services.
I have no idea about this question. I wouldn't do that. I would use the methods the public API exposes access to. But, I've never written my own API, let alone on the scale of Twitter or foursquare.
I hope this helps.
First of all, maybe you need some more info about what an API is: please take a look at the Wikipedia api page.
To answer to you questions (these are only general thoughts and not best practices):
An API, in this case, is a way that a developer uses to access a webservice, and it's not the service itself.
The websites you mention are not using their own APIs, as these APIs are meant for remote users (clients), and offer limited data sets, while the websites need maximum performance, access to the full database, and (almost) always use server-side code. The websites you mentioned, probably use other, server-side, high-performance APIs.
See the previous point: although it depends highly on which APIs you use, what you call "traditionally built websites" (that is, web applications using server-side APIs) can afford higher performance than websites totally built on top of remote APIs, because they do not depend on the bottleneck of the network connection (because, again usually, the web server and the database server either run on the same machine, or communicate faster than the client's browser and the server).
The reason that would make most people choose to develop a webapp the traditional way is that free APIs provide limited functionality (e.g. Google custom Search, limited to 100 reults).
I've been reading about "web services" here on SO, on Wikipedia, Google, etc., and I don't quite understand what they are. What is the plain English definition/description?
If I make a simple website using PHP that just, say, prints a random integer to the page... is this a "web service"? If not, why not?
A simple definition: A web service is a function that can be accessed by other programs over the web (HTTP).
For example, when you create a website in PHP that outputs HTML, its target is the browser and by extension the human reading the page in the browser. A web service is not targeted at humans but rather at other programs.
So your PHP site that generates a random integer could be a web service if it outputs the integer in a format that may be consumed by another program. It might be in an XML format or another format, as long as other programs can understand the output.
The full definition is obviously more complex but you asked for plain English.
Simplified, non-technical explanation:
A web serivce allows a PROGRAM to talk to a web page, instead of using your browser to open a web page.
Example:
I can go to maps.google.com, and type in my home address, and see a map of where I live in my browser.
But what if you were writing a computer program where you wanted to take an address and show a pretty map, just like Google maps?
Well, you could write a whole new mapping program from scratch, OR you could call a web service that Google maps provides, send it the address, and it will return a graphical map of the location, which you can display in your program.
There is a lot more to it, as some of the other posts go into, but the upshot is that it allows your application to either retrieve information FROM, or submit information TO some resource. Some other examples:
You can use a web service to retrieve information about books at Amazon.com
You can use a similar web service to submit an order to Amazon.com
You could CREATE a web service to allow outside applications to find out about product information within your company
you could create a web service to allow outside applications to submit orders to your company.
Yes that is a simple web service.
Web services are really nothing more than a request/ response mechanism that allows a client to remotely access/ modify data. There are formal standards for web services (SOAP, SOA etc), but your simple page is a service too.
The main downside to printing it to a page is that your service would return HTML. Preferable data formats are JSON and XML, because most client frameworks (and server frameworks) are designed around using JSON and XML.
So if you modified your service to return:
<RANDOM>some random number</RANDOM>
rather than:
<HEAD>...</HEAD>
<BODY>some random number</BODY>
then it would be more useful to most clients
In over simplified terms a web service is something that provides data as a service over the http protocol. Granted that isn't alway the case....but it is close.
Standard Web Services use The SOAP protocol which defines the communication and structure of messages, and XML is the data format.
Web services are designed to allow applications built using different technologies to communicate with each other without issues.
Examples of web services are things like Weather.com providing weather information for that you can use on your site, or UPS providing a method to request shipping quotes or tracking of packages.
Edit
Changed wording in reference to SOAP, as it is not always SOAP as I mentioned, but wanted to make it more clear. The key is providing data as a service, not a UI element.
A web service differs from a web site in that a web service provides information consumable by software rather than humans. As a result, we are usually talking about exposed JSON, XML, or SOAP services.
Web services are a key component in "mashups". Mashups are when information from many websites is automatically aggregated into a new and useful service. For example, there are sites that aggregate Google Maps with information about police reports to give you a graphical representation of crime in your area. Another type of mashup would be to take real stock data provided by another site and combine it with a fake trading application to create a stock-market "game".
Web services are also used to provide news (see RSS), latest items added to a site, information on new products, podcasts, and other great features that make the modern web turn.
Hope this helps!
The best plain English explanation comes from using an analogy:
Web pages allow people to communicate and collaborate with each other.
Web services allow programs to communicate and collaborate with each other.
Your PHP example is a web service by that definition, because the output could be consumed by another program. But in reality, HTML screen-scraping is not a reliable or maintainable way of producing web services.
For most sites you have HTML pages that you visit when you use your browser. These are human-readable pages (once rendered in your browser) where a lot of data might be crammed together, because it makes sense for humans.
Now imagine that someone else want to use some of that data. They could download your page and start filtering out all the "noise" to get the data they wanted, but most websites are not built in a way where data is 100% certain to be placed in the same spot for all elements, so in addition to being cumbersome it also becomes unreliable.
Enter web services.
A web service is something that a website chooses to offer to those who wish to read, update and/or delete data from your website. You might call it a "backdoor" to your data. Instead of presenting the data as part of a webpage it is provided in a pre-determined way where some of the more popular are XML and JSON. There are several ways to communicate with a webservice, some use SOAP, others have REST'ful web services, etc.
What is common for all web services is that they are the machine-readable equivelant to the webpages the site otherwise offers. This means that others who wish to use the data can send a request to get certain data back that is easy to parse and use. Some sites may require you to provide a username/password in the request, for sensitive data, while other sites allow anyone to extract whatever data they might need.
A web service is a collection of open protocols and standards used for exchanging data between applications or systems. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards (XML, SOAP, HTTP).
All the standard Web Services works using following components:
SOAP (Simple Object Access Protocol)
UDDI (Universal Description, Discovery and Integration)
WSDL (Web Services Description Language)
It works somewhat like this:
The client program bundles the account registration information into a SOAP message.
This SOAP message is sent to the Web Service as the body of an HTTP POST request.
The Web Service unpacks the SOAP request and converts it into a command that the application can understand.
The application processes the information as required and responds with a new unique account number for that customer.
Next, the Web Service packages up the response into another SOAP message, which it sends back to the client program in response to its HTTP request.
The client program unpacks the SOAP message to obtain the results of the account registration process.
Simple way to explain web service is ::
A web service is a method of communication between two electronic devices over the World Wide Web.
It can be called a process that a programmer uses to communicate with the server
To invoke this process programmer can use SOAP etc
Web services are built on top of open standards such as TCP/IP, 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.
Webservice is a technology by which two or more remote web applications interact with each other over network/internet. It can be implemented using Java, .net, PHP etc.
Features of Web service:-
Using web services two or more systems exchange data over network. Data are exchanged either using XML or JSON.
Any web service has two parts Server end where the service is deployed and the client part where the service is accessed by its clients. Any web service can have multiple clients. When a travel portal is selling tickets of an airliner. Portal is client and the Airline is the server as it is selling its service.
Web services can be synchronous or it can be asynchronous also.A web application can interact with many web services but these web services are loosely coupled with their client web applications. That means any change in the parent application has little or no effect on the web services or vice versa.
Web services can carry attachment document also like PDF, Word etc. with its XML payload. Java provides separate API for this type of web services.
A web service always hides the internal complexity of the service to its clients. For an example, an airliner which is selling tickets via a third party portal is only gathering end user info via a web service and in return it is providing ticket. The portal which is selling ticket doesn't have to bother about the internal complexity of the airlines ticket reservation systems.
A web service can be of fire and forget type or it can return something. Suppose, a web application just want to send some info to a third party application. The sender doesn't need any acknowledgement from the receiver. In this type of scenario we need a fire and forget type of web service.
A web service, as used by software developers, generally refers to an operation that is performed on a remote server and invoked using the XML/SOAP specification. As with all definitions, there are nuances to it, but that's the most common use of the term.
An operating system provides a GUI (and CLI) that you can interact with. It also provides an API that you can interact with programmatically.
Similarly, a website provides HTML pages that you can interact with and may also provide an API that offers the same information and operations programmatically. Or those services may only be available via an API with no associated user interface.
Well,
As #Vincent Ramdhanie has said that a web service is not meant to be seen / consumed by end user but another program. So technically logic in your program will be:
In case of acting as a normal program
user on website -> HTML/JS/JQuery etc -> give me a random number ->ur program
Now
ur program -> generate random number -> generate HTML and encapsulate o/p -> go back to user
but in case of web service the flow changes a little:
user -> my application -> XML/JSON/some other format -> give me a random number ->ur program
Now
ur program -> generate random number -> generate XML/JSON/some other format -> my application -> generate HTML and encapsulate o/p -> go back to user
Hope this helps :)
A simple definition would be an HTTP request that acts like a normal method call; i.e., it accepts parameters and returns a structured result, usually XML, that can be deserialized into an object(s).
Web services are almost like normal a web page. The difference is that they are formatted to make it very easy for a program to pull data from the page, to the point of probably not using any HTML. They generally also are more reliable as to the consistency of the format, may use a different formal process to define the content such soap or raw xml, and there is often also a descriptor document that formally defines the structure for the data.
A way of sending a message to invoke an operation on another computer. The difference between web services and previous methods is what gets sent over the wire is standardized at a higher level.
Old way: describe endians, encoding, port numbers, etc.
Web Service: URL, XML
Web Service is like a medium of commuication between two unrelated programs. The programs use a specified protocol(Usually Simple Object Access Protocol (SOAP)) as medium to understand what REQUEST/RESPONCE they are to process/execute on there respective end.
A web service defines a contract of actions that a server will perform for you. The format and protocol doesn't really matter, but you should have some set definition of how the communication happens.
In your example, it depends, if that is being used in another application that reads that number, yes it is service, otherwise, it's just a webpage with a number.
In simple words Web service could be any simple program ex: add two numbers which should be published over the UDDI and can be consumed by another program.WSDL will have the endpoint to locate the webservice and also the binding and port details.
'Web Service' is composed of two words,'Web' and 'Service'.
What is 'Web'? 'Web' means 'World Wide Web'.
'Service' for what? Not for Human,if so,it's 'Web Page',such as text,images,video etc.
It's for Programs to communicate through the Internet using the same technology the 'Web' used,such as TCP,HTTP etc.
'Service' also means it provides some functions,like the 'Service Layer' in CRUD.
There are mainly two types:
1. SOAP(Simple Object Access Protocol)
2. RESTful(Representational state transfer)
Without prejudice to other definitions I would say that a web service is software system that allows for inter-operable machine-to-machine / application-to-application interaction over a network. This generic definitions would also help consider REST architectures to be a web service as they provide similar functionality albeit being an architectural style unlike the SOAP which is a fully defined protocol.