All You Need to Know about REST APIs - ByteScout
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All You Need to Know about REST APIs

Representational Stateless Transfer APIs – popularly called REST or RESTful APIs – are the most commonly used web services currently in use. RESTFUL APIs are primarily application programming interfaces that allow developers to incorporate HTTP requests to provide communication services in different web technologies. Put simply, RESTful APIs are primarily web services that allow efficient communication between two systems.

  1. REST, don’t SOAP
  2. Isolated and Secure
  3. Our solution
  4. Efficiency at REST
  5. RESTful Authentication
  6. HATEOAS REST APIs
  7. Idempotent
  8. Conclusion

In one sense, they are no different from normal web URLs that you use to access content on the internet every day. However, they differ in one small aspect, which is that they give you the ability not only to make connections but to pass on additional information to the server. This is helpful as it allows developers to integrate certain functions to their API which would not otherwise be possible, particularly encryption, in an efficient way that does not use too much bandwidth.
In a typical Rest URL, this additional data would be appended after the “?” sign, and each individual request is separated by the & sign.
REST APIs offer certain advantages over other approaches, most of which are to do with the efficiency of code and of operation (see below).

PDF.co REST API (former ByteScout REST API) allows working with PDFs and barcodes, to sign PDF documents online as well as enables various conversions – HTML to PDF, PDF to TXT, PDF to CSV and more.

REST, don’t SOAP

Before the arrival of REST services, SOAP was the prevalent medium of communication. SOAP (Simple Object Access Protocol) was a bandwidth-heavy protocol that required far higher bandwidth use for applications and objects to communicate over the network. The reason for this was actually based on a good design need: SOAP allows the messages being sent over the network to be encrypted, which has been important in digital communications for decades and never more so today. Unfortunately, SOAP’s architecture meant that even simple messages such as “Hello World” had large sizes as compared to RESTful APIs, in order to embed the necessary encryption in the data. By comparison, due to their more efficient coding, REST services only retain a small portion of the bandwidth for themselves; which allows them to be far better at supporting internet applications.
SOAP also lacks portability, as it requires a program to be installed on the client as well as the server-side to allow communication between the two – to put it another way, the payload of a SOAP message can only be read by a specific program tailored for clients and servers. Given the breadth and variety of different platforms and environments being used on the internet today, a proprietary need like this is a killer for both usability and broad appeal.

Isolated and Secure

REST, by contrast, works efficiently by allowing invocation of services from servers, and authorization by isolated unique tokens. Given below is a code snippet that allows the invocation of a REST service that queries the server for a credential, parses it, and returns it as an isolated token to be used by the program.

private String getToken()
{
String url = host + "/identity/oauth/token?grant_type=client_credentials&client_id=" + clientId + "&client_secret=" + clientSecret;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.ContentType = "application/json";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream resStream = response.GetResponseStream();
StreamReader reader = new StreamReader(resStream);
String json = reader.ReadToEnd();
//Dictionary<String, Object> dict = JavaScriptSerializer.DeserializeObject(reader.ReadToEnd);
Dictionary<String, String> dict = JsonConvert.DeserializeObject<Dictionary<String, String>>(json);
return dict["access_token"];
}

Our solution

ByteScout’s expertise with REST Cloud APIs led us to realize that there was a real need in the market for a REST product which allowed developers a broad range of functionality, including the ability to work in and from various formats to PDF, or vice versa (with data extraction and to convert files from one format to another). Formats for PDF conversion supported by our REST Cloud API include TXT, JSON, XML, HTML, PNG, and JPG, as well as allowing digital signing, splitting, and merging of PDF files. Our REST Cloud API also allows developers to create simple QR codes or barcodes for data-sharing and integration of assets across formats.

Knowing the breadth of our development community, we wanted to make sure that our REST Cloud API provided access and SDKs for a range of usage cases, and the SDKs we have currently include Javascript, PHP, Python, .NET, Ruby, Android, and Objective-C.

Efficiency at REST

Invoking resources using REST is fairly simple, as REST treats each resource on the network as a black-box, and doesn’t concern itself with the states of each individual call, making each call stateless.
Stateless calls mean that REST APIs are extremely suitable for use with Cloud applications because they allow safe and secure redeployment of the software components of a cloud application in case the deployment fails the first time, in the case of network problems, or in the case of an insecure connection.
It also has an efficiency benefit in that it does not create or rely on a record of specific calls and their specific status. Calls can be made at any time, as REST calls don’t require the results of the previous transaction to be saved by the server or the client, meaning that calls can be directed to the server without keeping track of the sequence of the calls made, leading to far greater efficiency.

RESTful Authentication

To illustrate how easy authentication can be using REST, here is a code sample which provides the functionality of basic authentication for a program using REST APIs:

public class BasicAuth {
public static void main(String[] args) throws MalformedURLException, IOException {
String baseURL = "{base url}/rest/latest/";

// Username and password should be stored according
// to your organization's security policies
String username = "API_User";
String password = "********";
String auth = Base64.getEncoder().encodeToString((username + ":" + password).getBytes());

String resource = "projects";
URL url = new URL(baseURL + resource);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setRequestProperty("Authorization", "Basic " + auth);

InputStream content = connection.getInputStream();

BufferedReader in = new BufferedReader(new InputStreamReader(content));
System.out.println(in.readLine());
}
}

HATEOAS REST APIs

HATEOAS means Hypertext As The Engine Of Application State. It indicates that hypertext should be applied to locate your route through the API. It is a limitation or restriction of the REST application structure that holds the RESTful method different from most other system application designs. The word “hypermedia” applies to any material that includes links to application forms of media like images, videos, and text. In this, a client communicates with a REST API completely through the acknowledgments produced dynamically by the server.

The REST design method allows users to utilize the hypermedia links in the acknowledgment contents. It enables the client to operate to the proper resources by crossing the hypermedia links. Now, going through the hypermedia links is almost the same as an internet user browsing exploring, or visiting web pages by clicking the appropriate hyperlinks to reach a definitive object. The following example is displaying the use of this:

For example, the below-written JSON response may be from an API like HTTP GET http://api.mydomain.com/admin/dept/20

{
"deptId": 20,
"deptName": "Admin",
"locationId": 3500,
"mgrId": 250,
"links": [
{
"href": "20/emp",
"rel": "emp",
"type" : "GET"
}
]
}

In the above example, the reply delivered by the server includes hypermedia links to emp resources 20/emp, which can be crossed by the client to understand employees relating to the department. The benefit of the above method is that hypermedia links returned from the server run the application’s environment and not the other way around.

Idempotent

Now, including idempotency is an essential component of developing strong and predictable APIs. In fundamental words, idempotence is a situation where how many occasions the operation may be completed but the result remains the same. For example, take a(q) = q*q, how many occasions you may run a(3) it will always return 9. This call is idempotent.

Networks are often unpredictable, in situations where an API client may send and call but because of a technical problem does not get the response. This could not be the case in the GET request where it can retire but it could be a problem for non-idempotent HTTP techniques such as POST. That is why GET, PUT, DELETE, HEAD, OPTIONS, and TRACE are idempotent and POST is not idempotent.

To explain this, suppose we have a DELETE method, which is described as idempotent. Now think a client executes a DELETE call to remove a resource from the server. The server accepts the call, the resource gets removed and the server gives 204. Then the client returns the same DELETE request and, as the function has already been removed, the server responds with 404.

Conclusion

While REST APIs are very powerful, the fundamental fact about their function is that they are efficient and secure. REST APIs allow the stateless transfer of data with a maximum available bandwidth for use, allowing REST APIs to be extremely suitable for use in web technologies as well as cloud services, and providing a solid, secure, efficient backbone for web and cloud services of a variety of types.

   

About the Author

ByteScout Team ByteScout Team of Writers ByteScout has a team of professional writers proficient in different technical topics. We select the best writers to cover interesting and trending topics for our readers. We love developers and we hope our articles help you learn about programming and programmers.  
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