An API stands for Utility Programming Interface. It serves as a gateway for purposes to entry some sources from different purposes.
The benefit of utilizing an API is to offer entry to third-party purposes in order that they will’t entry your entire knowledge of your utility. They’ll solely entry the info which you expose via your API.
The applying or a consumer who desires to entry the info is named a consumer, and the appliance which serves the info is named a server.
APIs are extensively used at this time in each software program structure. If you’re making use of for a front-end, back-end, full-stack, or community engineering function, then you can be requested a number of questions concerning APIs.
With that being mentioned, let’s discover a number of the most ceaselessly requested interview questions on REST APIs.
What Is REST?
Reply: REST is an architectural design that defines some constraints on the working of APIs. The APIs which observe the rules of REST are referred to as RESTful APIs. REST stands for Representational State Switch.
It’s not a protocol or a normal; as a substitute, it’s an structure that can be utilized to implement APIs in varied methods.
It gives excessive flexibility and freedom to builders, and that’s why it’s extensively used to develop APIs. Listed below are a number of the rules of a REST structure:
- Separation of Shopper & Server: In a RESTful API, the consumer mustn’t have an effect on the server in another approach aside from requesting knowledge via a URI (Uniform Useful resource Identifier). In the identical approach, the server mustn’t modify the content material of the consumer in any approach.
- Statelessness: When two separate requests are made, they don’t find out about one another. In different phrases, the requests are stateless and don’t keep a state. If a request is fulfilled, it merely terminates. Each request is remoted from different requests.
- Layered Structure: The consumer or the server doesn’t know whether or not the request is being made on to the origin or an middleman utility. They solely care in regards to the response to the request.
- Caching: Knowledge or response will be cached on the consumer in addition to server facet to enhance efficiency and scalability. If there are frequent requests for a selected useful resource, then the response to that request will be cached and used when wanted.
What Are Some Key Traits of REST?
Reply: Key traits or options of REST are:
- Flexibility: You’ll be able to transfer from one server to a different, and it gained’t change something as a result of the API will ship the identical response for a selected request. Additionally, you’ll be able to add as many endpoints as you need for various kinds of knowledge.
- Scalability: Caching improves scalability because of the responses being saved for later use. It decreases the load on the server and in addition reduces latency.
- Authorization: With the assistance of the Authorization Header, you’ll be able to specify the credentials which the server can use to authorize the request.
- Statelessness: That is a very powerful function of REST as a result of it prevents requests from understanding what’s taking place with different requests. Requests are remoted and terminated as quickly as they’re fulfilled.
What Are Sources in a REST Structure?
Reply: Sources are entities on which totally different operations are carried out, reminiscent of retrieving, updating, or deleting. They’re the essential constructing blocks of REST structure.
For instance, in case you think about a web-based e-commerce retailer, the merchandise, customers in addition to metadata are thought of sources as a result of they are often operated on. Sources will be transferred to a different utility via API.
Point out Some Benefits and Disadvantages of a REST API.
Reply: The benefits of REST APIs are as follows:
- It’s easy to implement.
- Sources will be simply dealt with.
- It’s scalable due to client-server structure.
- Helps a number of knowledge switch media varieties reminiscent of XML and JSON.
Its disadvantages are:
- You can’t keep a state between requests.
- The true origin supply of the useful resource can’t be identified due to layered structure.
- Not good for advanced queries or requests.
Outline REST Template.
Reply: A REST template is a utility or a consumer via which you’ll be able to entry REST APIs within the Spring framework. It principally hides the boilerplate code you could have to write down in an effort to request a useful resource from a REST API.
What Is RESTful?
Reply: RESTful APIs or providers are interfaces that implement the REST (Representational State Switch) architectural fashion and work utilizing protocols reminiscent of HTTP.
What Are RESTful Net Providers?
Reply: RESTful internet providers are constructed to work greatest on the Net. Representational State Switch (REST) is an architectural fashion that specifies constraints, such because the uniform interface, layered structure, and statelessness, if utilized to an internet service, induce fascinating properties, reminiscent of efficiency and scalability, that allow providers to work greatest on the Net.
How Can You Check RESTful Net Providers?
Reply: To check a RESTful internet service, you need to use a REST consumer reminiscent of Postman or Thunder Shopper and question the online service you wish to check. Then, once you get a response, perceive the response; that’s the important thing half.
If you wish to check a posh API with many endpoints, you could have to interrupt down testing and carry out unit testing, integration testing, efficiency testing, and end-to-end testing.
Point out Some Options of RESTful Net Providers.
Reply: A few of the key options of RESTful internet providers are:
- Assist for a number of media varieties reminiscent of JSON and XML.
- Scalability
- Isolation of consumer & server
- Flexibility
Outline RESTful Root Useful resource Courses.
Reply: Root useful resource lessons are “plain outdated Java objects” (POJOs) which might be both annotated with @Path or have at the least one technique annotated with @Path or a request technique designator, reminiscent of @GET, @POST, @PUT, or @DELETE.
What Is URI?
Reply: URI stands for Uniform Useful resource Identifier. It’s a sequence of characters used to find or determine sources of an API or a service. It makes use of the identify or location of the useful resource to determine it, but it surely doesn’t depend on a selected technique or approach.
What Is Statelessness in REST?
Reply: Statelessness refers to 1 constraint utilized to an API during which any two requests can’t know what’s taking place with one another. In different phrases, the state of the requests isn’t maintained. If the request is fulfilled, it merely terminates after getting a response.
What Is JAX-RS?
Reply: JAX-RS is a Java API that lets you develop purposes in Java that use the REST structure. This API makes it simple to develop REST purposes in Java.
What Are the Key Annotations in JAX-RS API?
Reply: Annotations in JAX-RS are utilized by builders to brighten Java lessons in an effort to outline sources and strategies that may be carried out on these sources. Some key annotations of the JAX-RS API are:
@GET: It’s used for making GET requests in HTTP.@POST: It’s used for making POST requests in HTTP.@Path: It refers back to the relative path of a Java class.@QueryParam: It refers back to the question parameters of the URI or URL.
What Are Some Key Options ofJAX-RS API?
Reply: Options of JAX-RS are:
- Shopper-side caching
- Server-side caching
- Question string customization
- Runtime annotations
How Can the JAX-RS Purposes Be Configured?
Reply: A JAX-RS utility consists of at the least one useful resource class packaged inside a WAR file. The bottom URI from which an utility’s sources reply to requests will be set in one among two methods:
- Utilizing the @ApplicationPath annotation in a subclass of javax.ws.rs.core.Utility packaged inside the WAR
- Utilizing the servlet-mapping tag inside the WAR’s internet.xml deployment descriptor
What Are JAX-WS and JAX-RS?
Reply: JAX-WS is a Jakarta XML Net Providers API used for creating APIs utilizing Easy Object Entry Protocol (SOAP) – an XML-based messaging protocol.
Alternatively, JAX-RS is a Java API used for creating internet providers utilizing the REST structure.
What Are HTTP Standing Codes?
Reply: Standing codes are nothing however a option to talk the standing of the response despatched by the server to the consumer. They’re current within the response headers despatched by the server.
The consumer is in a position to determine if the request has failed or been fulfilled or if there’s something flawed with the response through the use of the standing codes.
Listed below are some frequent standing codes of HTTP:-
200– It stands for “OK” key phrase. It implies that the request has been fulfilled, and the response is alright.404– It stands for “Not Discovered”. This implies a useful resource isn’t current on the server or an endpoint doesn’t exist.500– It stands for “Inside Server Error”. This normally occurs when the server can’t generate the proper response, or there’s an error that isn’t explicitly thrown.503– It stands for “Service Unavailable”. It implies that at present, the server can’t course of any requests, in all probability as a result of it’s lifeless or isn’t working due to request overload. It may well additionally happen when the server is up for upkeep.
What Are HTTP Strategies?
Reply: HTTP strategies are used to carry out a sure kind of motion on a selected useful resource of an API. For instance, if you wish to fetch a listing of films from a film assortment API, then you need to use the GET technique supplied by HTTP. If you wish to replace the info, you need to use the POST technique supplied by HTTP.
Steadily used HTTP strategies are as follows:
- GET: Requests utilizing GET ought to solely retrieve knowledge.
- POST: It updates the useful resource by sending a newly up to date useful resource to the server.
- DELETE: It deletes the desired useful resource.
- PATCH: It partially modifies the useful resource.
How Does HTTP Primary Authentication Work?
Reply: Authentication is a course of to confirm the authenticity of a consumer to take care of knowledge safety. In HTTP, authentication works via an Authorization Header, which is shipped by the consumer.
Authorization Header consists of the username/id and password of the consumer, which is then verified by the server, and entry is granted.
One vital factor to notice right here is that when utilizing HTTP authentication, the channel via which the credentials move ought to be encrypted and safe.
You’ll be able to safe the channel utilizing the SSL layer, which is built-in into HTTPS. So, it is strongly recommended to make use of HTTPS as a substitute of easy HTTP when coping with credentials.
What Are the Core Parts of HTTP Request?
Reply: An HTTP request consists of the next parts:
- Request line: It’s the primary line in any request and consists of the HTTP technique, the trail or endpoint, and the HTTP model quantity.
- Headers: HTTP headers are used to offer metadata of the request.
- Physique (Optionally available): This part is just current for a number of the request strategies. It’s not required for GET requests, but it surely’s required for POST requests. It’s the precise message of the request.
What Are the Core Parts of HTTP Response?
Reply: An HTTP response consists of the next parts:
- Standing: It refers back to the HTTP standing code which is shipped by the server.
- Headers: Identical to requests, responses even have their respective headers, which give helpful details about the response.
- Message: That is the precise knowledge that’s despatched by the server to the consumer for requesting a selected useful resource.
What Is the Distinction Between REST and AJAX?
Reply: AJAX is a consumer via which you’ll be able to entry RESTful APIs. It’s used to ship asynchronous requests utilizing JavaScript.
REST, or Representational State Switch, is an structure that may be applied to create RESTful APIs. In brief, to ship HTTP requests, you need to use AJAX which serves as a consumer, however if you wish to implement RESTful APIs, then it’s important to use REST structure.
What Is the Distinction Between SOAP and REST?
Reply: Representational State Switch, or REST, is an structure with minimal constraints to create APIs. SOAP, or Easy Object Entry Protocol, is a protocol with strict necessities to implement an API.
REST is extra versatile and simple to make use of than SOAP. XML-based messaging is utilized in SOAP, whereas in REST, you need to use many knowledge switch varieties reminiscent of JSON, XML, and so forth. As in comparison with SOAP, REST is extra light-weight and quick.
SOAP internet providers have built-in safety, which is one benefit of utilizing SOAP over REST, however the added options additionally make it advanced and heavy to make use of.
What Is the Distinction Between PUT and POST?
Reply: POST is an HTTP request technique that sends some knowledge to the server. In the event you make a number of POST requests for a selected useful resource, then there will be negative effects to your knowledge. For instance, if you wish to add an article to a set, in case you make a number of POST requests, a number of articles might be added to the gathering resulting in redundant articles.
PUT is an HTTP request technique that sends knowledge to the server for a selected useful resource however solely updates the info as soon as. In the event you ship a number of PUT requests for a selected useful resource, no negative effects will happen, and the info might be added solely as soon as. In PUT, if the useful resource doesn’t exist, it can create a brand new one, and if it exists, it can replace the present one.
PUT is idempotent, whereas POST isn’t.
What Is a Payload?
Reply: A payload in a REST API is just the physique of the request despatched from the consumer to the server. It’s the info you wish to ship to the server and get a response.
What Is the Most Payload Dimension That Can Be Despatched in Publish Strategies?
Reply: There isn’t a default restrict set by the HTTP protocol itself. The restrict can rely upon the utmost restrict of the consumer or the server, whichever is the minimal.
Whereas Creating URI, What Are the Finest Practices That Must Be Adopted?
Reply: A few of the key factors you want to bear in mind whereas designing URIs are:
- Keep away from utilizing file extensions
- Be according to all URIs
- Divide the URIs into domains and subdomains for various units of sources
- It’s best to use hyphen or underscore to separate phrases in sentences embedded in URIs
- It’s best to use the ahead slash to point a hierarchy of sources
- Encode a URI utilizing correct encoding
- Attempt to make the URI human-readable
What Are Idempotent Strategies?
Reply: Idempotent HTTP strategies have the identical impact on the server regardless of sending a number of similar requests. For instance, in case you ship a number of similar DELETE requests for a selected useful resource, the useful resource gained’t change on each request; it can replace as if just one request has been despatched.
A few of the idempotent strategies embrace:
- PUT
- DELETE
- GET
- HEAD
- OPTIONS
What Is Postman?
Reply: Postman is an API improvement device to develop, modify, and check APIs. It gives many options to construct and check APIs shortly with out the necessity to arrange a consumer.
What Are Cache-Management Headers?
Reply: The Cache-Management header consists of directions or directives to configure caching in browsers and servers. It tells the browser or the server what to cache and the way lengthy it ought to be cached earlier than being requested via the community request.
The Cache-Management header consists of the next directives:-
- max-age
- no-cache
- non-public
- public
- no-store
- immutable
Outline Messaging in RESTful Net Providers.
Reply: Messaging in RESTful internet providers refers back to the consumer sending an HTTP Request to the server, to which the server responds with an HTTP Response. This communication between the consumer and the server is known as messaging.
What Is the Distinction Between Monolithic, SOA, and Microservices Structure?
Reply: In a monolithic structure, every thing is managed in a single place. The consumer facet, the server, in addition to the database are all managed from a single place. That’s why it’s referred to as monolithic as a result of the phrase “monolith” refers to a single block or stone.
SOA stands for Service-Oriented Structure. On this structure, totally different facets of the appliance are managed by totally different providers, that are additionally software program. So, it’s a mixture of a number of service software program modules. Integration is the important thing a part of this structure.
Microservices structure is much like SOA, however in contrast to SOA, it has a number of autonomous software program applications which discuss to one another utilizing APIs. Not like monolithic structure, every thing right here is autonomous and, to some extent, unbiased.
How Does Microservice Structure Work?
Reply: In a microservice structure, the purposes are divided into smaller subunits which might be unbiased of one another and work on their very own, however they impart with one another through a well-defined set of APIs.
Some advantages of microservices structure embrace agility, flexibility, scalability, unbiased applied sciences, reusable providers, and simple deployment.
What Is CRUD?
Reply: CRUD stands for Create, Learn, Replace, Delete. These are the operations that may be carried out on a selected useful resource. The API which helps all of those operations is named a CRUD API. These are essentially the most primary operations which will be carried out by an API on a useful resource.
What Is Caching?
Reply: Caching is a way of storing a response or a request on the consumer or the server for it for use once more later.
Responses are typically cached on the consumer as a result of if the consumer makes the identical request a number of instances in a short while interval, then it is unnecessary to request the response once more over the community and waste the bandwidth.
What Is the Use of @RequestMapping?
Reply: It’s an annotation within the spring framework which is used to map internet requests onto particular handler lessons and/or handler strategies.
What Does @PathVariable Do?
Reply: The @PathVariable annotation within the spring framework is used to extract the worth of the template variables and assign their worth to a way variable.
Outline HttpMessageConverter.
Reply: When an HTTP request (or parts of it) must be transformed into a kind wanted as an argument for a handler technique or when the worth returned by a handler technique must be transformed not directly to create an HTTP response, HTTP message converters are used.
What Instruments Are Required to Check Your Net API?
Reply: Some instruments which will help you in API testing are as follows:
- Postman
- Relaxation Assured
- Relaxation Sharp
- Katalon
- ReadyAPI
- Apigee
Closing Phrases
These days, APIs have turn out to be extraordinarily in style due to the arrival of the web. One more reason REST APIs are in style is that they’re simple to develop and simple to make use of.
If you’re getting ready for an interview, think about the above questions on REST APIs that may be requested in your interview.
Subsequent, you’ll be able to verify learn how to scrape a web site utilizing Geekflare’s Net Scraping API.