I want to know what’s the difference between a web service (web api) and a rest api
I have learnt till now only GET and POST methods in backend to communicate with my apps but people always talk about PUT DELETE UPDATE & REST etc I am unable to understand the benefits and meaning.
What is the difference between a rest api and web api
Neither of these terms is well enough defined to assert with any confidence "the" difference.
REST is an architectural style; the most important application of that style is the world wide web. The web has been so catastrophically successful that there really hasn't been a second REST application - if you need what REST offers, you use the web, because the hard work has already been done for you.
I am unable to understand the benefits and meaning.
For every standardized HTTP method, you can use the HTTP method registry to find the reference that defines the meaning of the method.
Most of the methods that people talk about on a regular basis have their meanings defined by RFC 7231.
The benefit comes from the fact that the meanings of the different methods are standardized; the provide certain semantic guarantees that allow general purpose components to do clever things.
For example, knowing that a method has idempotent semantics means that we can resend the http request when we don't get a response the first time, this is an important constraint when your network is unreliable. Because that's true of all idempotent requests, regardless of which URI is being targeted, we can build a retry into the browser.
It may help to think about POST as "the" basic message, and all of the others as being specializations
GET is a specialization of POST that is used to retrieve copies of representations
HEAD is a specialization of GET that is used to retrieve metadata
PUT is a specialization of POST that is used for "upserting" new representations
PATCH is a specialization of POST that applies patch documents to a resource
My aim is to select some text from a web page, start a google chrome extension and give the text to a google cloud api (Natural Language API) in my case.
I want to do some sentimental analysis and then get back the result to mark/ highlight positive sentences in green and negative ones in red.
I am new to this and do not know how to start.
The extension consists of manifest, popup etc. How should I call an API from there that does Natural Language Processing?
Should I create a Google Cloud Application with an API_KEY to call? In that case I would have to upload my credentials right?
Sorry sounds a bit confusing I know but I just don't know how I can bring this 2 things together an would be more than happy about any help
The best way to authenticate your app will depend on the specific needs and use cases of your application. You can see an overview of all the different methods here.
If you are not planning on identifying users nor on using a back end server that handles authenticating (as I assume to be your case), the best option would indeed be to use API keys. They do not identify the user, but are enough for the Natural Language APIs.
To do this you will need to create an API key for the services you want and add the necessary restrictions to make the key as secure as possible. Detailed instructions on how to do this and how to use the key in a url can be found here.
The API call could be made from within the Chrome extension with any JavaScript method capable of performing POST requests. For example using XMLHttpRequest or the Fetch API. You can find an example of the parameters that need to be included in the request here.
You may run into CORS issues when making the request directly from the extension. I recommend reading this answer, where a couple of workarounds for these issues are suggested.
I'm new to this game so I might be misunderstanding things. Actually, if someone tells me that I'm misunderstanding things, it will be a favor. Maybe this person will be considerate enough to show me the right path. But...
One of the "guidelines" or "best practices" of REST as it applies to Web Services (http://en.wikipedia.org/wiki/Representational_state_transfer#Applied_to_web_services) is that you should use the proper HTTP methods when making calls (did I misunderstand it?) to REST API's.
But looking at many API implementations on the web, what I see is that 100% of the calls made to them are actually GET calls that, depending on their URI, will be interpreted by the API as being of one of the HTTP verbs or methods.
So, for example, looking at the REST API documentation for Twitter (https://dev.twitter.com/rest/public) which, in principle, only defines two verbs/methods (GET and POST), actually have all calls sent as GET and, based on the URI in the GET call, are interpreted by the API and acted upon.
Example:
GET statuses/lookup: https://api.twitter.com/1.1/statuses/lookup.json
POST statuses/update (PUT?): https://api.twitter.com/1.1/statuses/update.json
In both cases, the call itself was made using GET and the last part of the URI defined it as a real GET or as a POST.
In summary, to be truly RESTful, shouldn't client side implementations of REST API's for web services use the proper HTTP verbs/methods?
What am I missing?
You're missing a lot, but don't worry about it, most people are.
The fact is that very few so-called REST APIs publicly available on the internet are really RESTful, mostly because they are not hypertext driven. REST became a buzzword to refer to any HTTP API that isn't SOAP, so don't expect for an API to really be RESTful just because it says it's a REST API. I recommend reading this answer.
From my experience, most API developers aren't aware what REST really is and believe any HTTP API that uses HTTP and avoids verbs in URIs is REST.
REST is defined by a set of constraints. Among them is the uniform interface, which in simple terms means that you should not change the expected behavior of the underlying protocol. REST isn't coupled to any particular protocol, but since it's common to be used with HTTP, they get convoluted sometimes.
HTTP has very well defined semantics for the GET, POST, PUT, DELETE, PATCH and HEAD methods, and the POST method has its semantics determined by the server. Ideally, a REST API should respond to the methods other than POST exactly as determined in the RFC 7231, but as you noticed, there are many APIs who call themselves REST but don't do that. This happens for many reasons. Sometimes there's a simple misunderstanding about the correct semantics, or it's done to keep consistency, or because of backwards compatibility with intermediaries that don't support all methods, and many other reasons.
So, there's a lot more that has to be done to be truly RESTful other than using the HTTP methods correctly. If an API doesn't get even that right, it needs to find another buzzword, because it's definitely not REST.
I can't exactly tell what your question is, but I believe there are some concepts that will help you. Allow me to elaborate...
You are correct that many APIs use a limited number of HTTP "verbs" in their API. GET/POST are the most common. PUT less so, and then all others (DELETE, HEAD, OPTIONS etc) are used with vanishing probabilities.
Dropbox Core API for file uploads allows optional PUT / POST and their stated reason is "For compatibility with browser environments, the POST HTTP method is also recognized."
Indeed the limitation is the browser. Popular web servers have no problem with all HTTP request methods and even made up ones. After all, the request method is just some string with regard to the web server.
HTML4 and HTML5 only allow GET and POST requests for form requests. If you want your API to be used through a browser at all - and hey why not, it sounds like a useful thing - then you're limited to GET/POST. For a useful discussion on this see: https://softwareengineering.stackexchange.com/questions/114156/why-are-there-are-no-put-and-delete-methods-on-html-forms
Further complicating things is the fact that REST is not an industry standard. There exists no RFC, ISO or other document detailing what a "compliant" implementation must and must not do. While many folks have been playing concepts related to REST for some time, the REST concept was "invented" in the PhD disseration of Roy Fielding. A fantastic read if you're interested in such things.
Yes, according to REST, APIs should be using the correct verbs. However, as long as the documentation is clear and all GET requests are idempotent, then life should continue smoothly.
(Source: I wrote PipeThru.com which integrates 40+ APIs, Dropbox and Twitter included)
I think that this link could give you some hints about the design of RESTful services / Web API: https://templth.wordpress.com/2014/12/15/designing-a-web-api/.
It's clear that not all Web services that claim to be RESTful are really RESTful ;-)
To be short, RESTful services should leverage HTTP methods for what they are designed for:
method GET: return the state of a resource
method POST: execute an action (creation of an element in a resource list, ...)
method PUT: update the complete state of a resource
method PATCH: update partially the state of a resource
method DELETE: delete a resource
You need to be also to be aware that they can apply at different levels, so methods won't do the same things:
a list resource (for example, path /elements)
an element resource (for example, path /elements/{elementid})
a field of an element resource (for example, path elements/{elementid}/fieldname). This is convenient to manage field values with multiple cardinality. You don't have to send the complete value of the fields (whole list) but add / remove elements from it.
Another important thing is to leverage HTTP headers. For example, the header Accept for content negotiation...
I find the Web API of Github well designed and its documentation is also great. You could browse it to make you an idea. See its documentation here: https://developer.github.com/v3/.
Hope it helps you,
Thierry
You are correct. If they want to be "RESTful", their API should respect the semantics of each HTTP method.
Roughly, REST is about method Information (what the server should do), scoping information (where the server should do it) and, I almost forgot to mention, hypermedia driven (make sure you check #PedroWerneck's great answer to this question as it talks about it a little more and referecences a blog post from Fielding on the matter).
What the API you mentioned does is have both method and scoping information in the URL. That would not fit the RESTful architecture very well, as it, in general terms, tells us to:
1) use the HTTP methods the proper way (respecting their properties, such as idempotency and others), and
2) use unique URIs to identify unique resources.
Point 1 says "use HTTP methods to convey method information" and point 2 says "use URIs to convey scoping information".
Again, if an API uses GET with a specific parameter in the URI to do something (and not get something), then it is using URI to convey method information.
Now, don't be alarmed. Most APIs out there are just RESTful-ish (like twitter's of flickr's), meaning they are an animal between REST and something else. That is not bad per se, it just means they will not fully benefit from what RESTful architectures (and HTTP) have to offer.
Remember that being RESTful isn't just a matter of fashion, it does have its benefits, such as statelesness, adressability, and so on. And those can only be fully achieved by using the HTTP verbs like they were supposed to be used.
About using POST instead of PUT, considering they have different properties (PUT is idempotent, POST is not), it is not bad to use POST, as long as it is uniformly designed, that is, a programmer should not wonder what POST will do for each and every URI in the API: they all should behave the same. (PUT does not suffer from that because it already is uniform.) I talked a little more about this - and quoted Roy Fielding's say on it - in another question (check out the "Wrapping Up" part).
Consider looking at REST Richardson Maturity Model topic.
This specification is about how much RESTful particular API is:
Level 0:
Simple GET and POST request to descriptive url
/getUserByName?name=Greg
Level 1:
Divide all content in resources and define actions in resource group
/user/getByName?name=Greg
Level 2:
Proper use of HTTP verbs.
GET /user/Greg
Level 3:
Use hypermedia controls
Different APIs in interent implement different maturity level of REST. That's why some APIs don't support all HTTP features.
Rest confuses me sometimes. I know that it involves creating an API layer over your data and then you make calls to that data through the API. The best way I think of Rest is that the actual Twitter website interfaces with the data-layer through API calls.
That made me wonder then: Is a backend-service like Parse also a Rest API to your data?
What might be the difference between Parse and say, building your own Rest API like this guy did: http://coenraets.org/blog/2012/10/nodecellar-sample-application-with-backbone-js-twitter-bootstrap-node-js-express-and-mongodb/ (he's getting some solid google rankings for his API tutorials).
A simple yes/no might answer the question, but providing details will really be appreciated.
I look forward to the answers.
Parse is built around a restful API just like most, if not all, other mBaaS out there.
A RESTful Api isn't just CRUD operations though nor is it the same thing as Parse. Parse is a company that provides a remote backend to developers using a RESTful api.
RESTful api !== BaaS
I have dealt with about 5 mBaaS and Parse isn't really one of them, but I've glanced at their API reference for JS and I think they use mongodb clusters. An mBaaS usually provides the developer the ability to have cloud storage, push notifications, server side code, easier social media integration, and mobile analytics. So it's not just any backend. Although there are some mBaaS, like Urban Airship, that only supply push notifications to developers.
A RESTful api at it's core usually has some key functions that are centered/wrapped around an httpRequest
They usually use "GET", "POST", "DELETE", and "PUT" to make all calls. Some allow the implementation of rpc for custom server logic. An mBaaS takes a lot of work to implement right and well. You can't build Parse in a Day. It takes a lot of planning and such. The differences between Parse and that guy in link are in the implementation, range of features, and purpose in general(the audience).
To better understand REST maybe look here you can also read the HTTP spec if you are feeling adventurous.
I have a website that revolves around transactions between two users. Each user needs to agree to the same terms. If I want an API so other websites can implement this into their own website, then I want to make sure that the other websites cannot mess with the process by including more fields in between or things that are irrelevant to my application. Is this possible?
If I was to implement such a thing, I would allow other websites to use tokens/URLs/widgets that would link them to my website. So, for example, website X wants to use my service to agree user A and B on the same terms. Their page will have an embedded form/frame which would be generated from my website and user B will also receive an email with link to my website's page (or a page of website X with a form/frame generated from my server).
Consider how different sites use eBay to enable users to pay. You buy everything on the site but when you are paying, either you are taken to ebay page and come back after payment, or the website has a small form/frame that is directly linked to ebay.
But this is my solution, one way of doing it. Hope this helps.
It depends on how your API is implemented. It takes considerably more work, thought, and engineering to build an API that can literally take any kind of data or to build an API that can take additional, named, key/value pairs as fields.
If you have implemented your API in this manner, then it's quite possible that users of this API could use it to extend functionality or build something slightly different by passing in additional data.
However, if your API is built to where specific values must be passed and these fields are required, then it becomes much more difficult for your API to be used in a manner that differs from what you originally intended.
For example, Google has many different API's for different purposes, and each API has a very specific number of required parameters that a developer must use in order to make a successful HTTP request. While the goal of these API's are to allow developers to extend functionality, they do allow access to only very specific pieces of data.
Lastly, you can use authentication to prevent unauthorized access to your API. The specific implementation details depend largely on the platform you're working with as well as how the API will be used. For instance, if users must login to use services provided by your API, then a form of OAuth may suffice. However, if other servers will consume your API, then the authorization will have to take place in the HTTP headers.
For more information on API best practices, see 7 Rules of Thumb When You Build an API, and a slideshow from a Google Engineer titled How to Design a Good API and Why That Matters.