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REST API（Representational State Transfer API）

  • Glossary

「REST API（Representational State Transfer API）」

This glossary explains various keywords that will help you understand the mindset necessary for data utilization and successful DX.
In this article, we will explain the "REST API," which is now widely used as a means of calling various functions via the Internet in the cloud era, and through it, we will think about what kind of IT and its thinking will be necessary in the future.

What is a REST API (Representational State Transfer API)?

REST API (Representational State Transfer API) is an architectural style of API that is widely used as a means of calling remote resources, such as various functions and data, via the Internet.
The specifications emphasize simplicity, making them easy to implement and use, and they are suitable for use on the Internet because they make good use of already widely used technologies such as the HTTP protocol. Following the "RESTful approach" that gave rise to this architectural style is sometimes called "RESTful."

What is an API?

API is an abbreviation for Application Programming Interface. Just as a mouse or keyboard is provided as an interface for people to use a computer, an API is an interface provided for external applications to use the functions and data of those applications or cloud services.

There is also an explanatory article on the API itself
⇒ API｜Glossary Vol.6

The situation before the advent of REST APIs

When you run a program on a computer to achieve something, various "function calls" are made. Almost all applications run by calling and using external functions, such as various OS functions, through "OS APIs." Even basic functions such as screen drawing and mouse operation are realized via APIs.

If you could call functions on other computers in addition to calling functions on your own computer, you could achieve even more. As computer networks became more widespread, such functions began to be used in practice. For example, there is "RPC (Remote Procedure Call)," a function that calls the functions of a program on a remote computer via a communications network.

Going further, if multiple computers could communicate and cooperate over a network, even more advanced things could be achieved. To achieve this, functions beyond simply being able to call the functions of other computers would be required. Functions would also be developed to enable the exchange of complex data and for computers to successfully find communication partners over the network and communicate smoothly. As a means to this end, full-fledged communication protocols with a full range of functions and the software (middleware) to realize them would also be developed.

Why is the "RESTful way of thinking" necessary?

As such, the development of functions that allow one computer to call and use the functions of another computer has progressed, but the REST API was a new concept proposed in response to this situation. Although these older protocols were full-fledged and equipped with a variety of functions, they tended to have complex specifications and were often cumbersome to use, requiring learning and the use of middleware, making it difficult to accomplish simple tasks.

As the cloud computing era approached and business activities using IT systems over the Internet began to flourish, there was a demand for new methods of implementing APIs that could "implement simple tasks in a simple way." This led to the proposal of a new architectural style for implementing APIs based on the "RESTful approach."

REST API（Representational State Transfer API）

REST APIs utilize the technologies and communication infrastructure that are prevalent on the Internet, and are implemented using the same concept as HTTP communication, the technology used when people browse the web in a web browser, to enable API calls over the Internet.

The same protocol as HTTP communication (web browsing)

The HTTP protocol mechanism, by which a web browser given a URL retrieves and displays an HTML document from a web server on the other side of the Internet, is used as the basis for realizing the API. In other words, it uses the same mechanism that humans use when browsing the web.

Not only is the HTTP protocol simple and easy to understand, but web browsing is so widespread that the things involved are overwhelmingly well-established.

Use the URI (URL) as is

For mail to arrive, addresses must be determined according to some rules, and a system for delivery based on those addresses must be created and maintained. The same is true when calling the functions of a communication partner on the other side of the Internet; some method is required to distinguish between the different partners and call them. To address this issue, we will simply use the "same system as a web browser URL" without creating a new system.

For example, the server you are communicating with is specified in a format like "www.example.com." Furthermore, if the computer has multiple functions that can be called, they are distinguished using the same mechanism as a URL. For example, a style like "www.example.com/users" allows you to specify multiple functions individually in an easy-to-understand manner.

Communications infrastructure can be used as is

Because it works in the same way as regular web access, the Internet's communications infrastructure can be used as is. The mechanism for reaching the other party using a URL can of course be used as is, the mechanism for secure communication using https can be used as is, and mechanisms for processing large amounts of access using cache can also be reused as is.

Because normal web browsing and communication are the same, there is no need to install new hardware or even change the settings on network devices. This means that those who want to use the API will have the infrastructure already in place around the world without having to set anything up themselves.

The "verb" used when calling is also the same as HTTP.

For example, with RPC, the mainstream style was to call the function name of the process you wanted to call by adding parameters. If you wanted information about all the members of a branch office, you would call it by specifying the individual "verb" that corresponds to what you wanted to do, such as "allMembers(branch office name)."

In contrast, REST uses the verbs "HEAD," "GET," "POST," "PUT," and "DELETE" defined in the HTTP protocol. Of these, "PUT" and "DELETE" are rarely used in normal web browsing, but the standard makes good use of those that are implemented.

If you reinterpret the meaning of these verbs as "GET (read data)," "POST (create data)," "PUT (update data)," and "DELETE (delete data)," you can directly correspond to the CRUD (Create, Read, Update, Delete) of database access. For example, if you do this, you will be able to use the same processing capabilities as general database access via the HTTP protocol.

The method of passing parameters also uses the HTTP method.

The method for passing parameters when calling the API also follows the HTTP protocol, and is the same as the method for passing parameters (and files) in a GET request or a POST request.

stateless

Like HTTP, REST APIs make API calls stateless. What is meant by "stateless" is that "the same request will return the same result" regardless of the context of previous or subsequent calls. Alternatively, each time an API call is made, the parameters included in the request themselves contain all the information necessary for that process.

This allows the party processing the API call to process only the request that just arrived and generate a response without referring to the context of previous or subsequent requests. Not only does this simplify implementation, but the same request will produce the same result, making it easier to utilize caching (which makes it easier to speed up processing and implement APIs with high loads).

The method of returning processing results is also HTTP style

The method for returning the results of processing from the API also uses the same method as the HTTP protocol. The paper proposing REST also suggested using HTML as the data format, and stated that using HTML would allow existing technologies to be used, such as communicating references to external resources using HTML styles (anchor tags, etc.).

In practice, results are often returned in JSON format (JSON/REST). XML is sometimes used, and CSV or image files are also sometimes returned. JSON originates from the data (object) description method used in JavaScript, a programming language that runs on web browsers, and has become widely used because it is not only an easy-to-process format, but also easy for people to read. In other words, JSON is a direct adaptation of a widely used technology that originated on the web.

How simple is it?

REST APIs are so simple that people can access them from a web browser. APIs used by programs usually cannot be called by human means; for example, people cannot directly communicate with Android APIs. However, with REST APIs, people can often make API calls using a web browser, and it is not uncommon for people to be able to read the returned results.

The world of REST APIs spreading across the Internet

This is not something that is noticed when using the Internet normally, but especially since the cloud era, a huge amount of functionality has been rapidly made available on the Internet as REST APIs.

The cloud era is also the era of REST APIs

Cloud computing has become increasingly popular in recent years, but cloud computing does not just mean adopting and using SaaS applications that can be used on a web browser; it also means using the many REST APIs that are publicly available on the cloud.

For example, how do major cloud services such as the huge AWS provide their many functions? Many of these functions are provided via REST APIs. In other words, using AWS means using REST APIs. Many other cloud services also provide various functions via REST APIs.

Leveraging REST APIs necessary for your business

The use of REST APIs will become increasingly important in the future, both as a means for companies to conduct business over the Internet and as a means for establishing cooperative relationships with other companies.

For example, if each company in a supply chain publishes the functions of its own system as a REST API, the companies can use those functions with each other, potentially realizing unprecedented collaborative relationships. In other words, advanced automation and the creation of ecosystems through REST APIs with other companies, such as the entire supply chain, can be realized.

You can also publish a REST API for your own business. You can offer the functions of your own system for a fee, or provide them free of charge and encourage external use of the API to create your own ecosystem. You can also provide an order acceptance function via API to streamline your business.

How to use the world of REST APIs in your company

Some people may think that REST APIs are easy to use and would like to try using them in their own company right away, while others may think that APIs require programming and would be impossible for their company to use.

Programming is basically required

As I mentioned at the beginning, an API is not something that people use, but rather an interface that applications use. In other words, it is a world that requires programming. There is a vast world of REST APIs on the Internet, but unfortunately, not everyone can easily use them.

"Easy to call" does not mean "easy to use"

As explained above, the REST API itself is a very simple mechanism, but whether or not the implementation of each API is easy to use is another matter. They may have complex specifications, and you may need to read and understand the documentation to use them.

Publishing your own API is not easy

The same thing can happen on the provider's side; if the API is not provided carefully, it may become very difficult for external parties to use and no one will use it, or it may become difficult to expand the API's functionality in the future.

Peripheral functions associated with API release, such as authentication and security

Publishing your own API offers great potential, but it also exposes your functions to the internet, which can lead to malicious attacks. This means that you will need authentication and security measures to appropriately restrict API access.

Still, REST APIs can be used as a means to connect

You may think that using REST APIs is difficult, but there are ways to make it possible. These are efforts that use connecting technologies such as "DataSpider" and "HULFT Square," known as "EAI," "ETL," and "iPaaS."

You can place and configure icons on the GUI and use them.

There is no need to write source code in a programming language; you can achieve the equivalent of programming by placing icons on the GUI and making the necessary settings. In addition to REST API calls, you can also access a wide variety of systems and data other than REST APIs, from on-site Excel files to mainframes.

You can make your own or use pre-made options.

You can call the REST API yourself using a "general-purpose connection adapter" and create and use it yourself, or if the API specifications are too difficult and require too much time and effort, or if you don't want to create it yourself, you can simply and conveniently use the connected service using a "dedicated connection adapter" that has been prepared in advance to make it easy to call existing REST APIs.

The created functionality can be published as an API.

With "HULFT Square," you can publish functions created on the GUI as REST APIs. If you have created a function that is necessary for your company and want to publish it as an API for reuse, or if you want other companies to use it as an API, you can create it on the GUI and publish it as a REST API.

Peripheral functions associated with the release of APIs, such as authentication and usage log acquisition

HULFT Square also provides the necessary functions for publishing APIs, such as authentication and API usage logging. You can use the functions already provided without having to develop them individually in-house.

No need to operate in-house as it is iPaaS

With DataSpider, you can operate it securely under your own management. With the cloud service (iPaaS) HULFT Square, you can use this "connecting" technology without having to operate it yourself. You can take advantage of the potential of APIs without the hassle of in-house implementation and operation.

API utilization made possible by "connecting" technology

Using APIs with this kind of "connecting" technology may seem like a desperate measure or a simple way to use them.

It is true that skilled engineers can take on more advanced challenges by utilizing APIs through programming and cloud services, but it is rare for skilled engineers to also have a deep understanding of the company's business.

When using APIs in business, it is the people on the front lines who can judge how a published API can be useful in their company's operations. Also, if a company wants to publish an API and do business, that means doing business through the API, so it is important to have business sense for things like what kind of API it should be, what functions can and cannot be used, and how to charge, and it is the people on the front lines who have the best sense for these things.

In other words, the ability for business people to "access the API world themselves" has huge business potential. Business speed increases if they can do things themselves rather than having to ask an engineer each time. Alternatively, securing skilled engineers in-house and then effectively combining this with efforts using "connecting" technology will likely lead to even better API utilization.

Related keywords (for further understanding)

  • EAI
    • It is a concept of "connecting" systems by data integration, and is a means of freely connecting various data and systems. It is a concept that has been used since long before the cloud era as a way to effectively utilize IT.
  • ETL
    • In the recent trend of actively working on data utilization, the majority of the work is not the data analysis itself, but rather the collection and preprocessing of data scattered in various places, from on-premise to cloud.
  • iPaaS
    • A cloud service that "connects" various clouds with external systems and data simply by operating on a GUI is called iPaaS.
  • API Platform
    • When providing an API, it is necessary to prepare not only the API itself but also peripheral functions such as authentication. Why such functions are necessary and what an API infrastructure is.

Are you interested in "iPaaS" and "connecting" technologies?

Try out our products that allow you to freely connect various data and systems, from on-premise IT systems to cloud services, and make successful use of IT.

The ultimate "connecting" tool: data integration software "DataSpider" and data integration platform "HULFT Square"

"DataSpider," data integration tool developed and sold by our company, is a "connecting" tool with a long history of success. "HULFT Square," a data integration platform, is a "connecting" cloud service developed using DataSpider technology.

Another feature is that development can be done using only the GUI (no code) without writing code like in regular programming, so business staff who have a good understanding of their company's business can take the initiative to use it.

Try outDataSpider/ HULFT Square 's "connecting" technology:

There are many simple collaboration tools on the market, but this tool can be used with just a GUI, is easy enough for even non-programmers to use, and has "high development productivity" and "full-fledged performance that can serve as the foundation for business (professional use)."

It can smoothly solve the problem of "connecting disparate systems and data" that hinders successful IT utilization. We offer a free trial version and online seminars where you can try it out for free, so we hope you will give it a try.


Why not try a PoC to see if "HULFT Square" can transform your business?

Why not try verifying how "connecting" can be utilized in your business, the feasibility of solving problems using data integration, and the benefits that can be obtained?

  • I want to automate data integration with SaaS, but I want to confirm the feasibility of doing so.
  • We want to move forward with data utilization, but we have issues with system integration
  • I want to consider data integration platform to achieve DX.

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