RESTful Web Services follow the REST architectural style. REST defines any simple interface. That transmits data through a standardized interface. It transmits data without an extra messaging layer. For example, Simple Object Access Protocol (SOAP). REST gives a set of design rules for creating stateless services. Those are looked at as resources. Each resource may be signified by its unique Uniform Resource Identifiers (URIs).
In this article, we will understand RESTful Web Services in depth.
The REST architectural style is developed for network-based applications. It is designed particularly for client-server applications. Similarly, it is designed for Internet-scale usage. Therefore, the coupling between the client and the origin server must be as loose as possible to provide facilitation to large-scale adoption.
This is gained with the creation of a layer of abstraction on the server by defining resources. That encapsulates entities, for example, files on the server. Therefore, hiding the underlying application details such as file server, database, etc. Though, the definition is even more common than that:
- Any information that may be named can be a resource
- An image, a database query,
- A temporal service, for example, “today’s weather in London”
- Even a collection of other resources.
This method enables the greatest interoperability between clients and servers in a long-lived Internet-scale environment. That environment crosses organizational boundaries.
Clients may just access resources using URIs. A representation of a resource is an important concept in REST. That is to make sure the responses may be interpreted by the widest possible number of client applications a representation of the resource is sent in hypertext format. Therefore, a resource is handled via hypertext representations transferred in messages between the clients and servers.
Six Architectural Constraints
- Uniform interface
- Layered system
- Code on demand (optional)
1. Uniform interface
This is the main constraint that differentiates between a REST API and a Non-REST API. It proposes that there should be a uniform way of association with a given server irrespective of device or type of application.
Below are four guidelines principle of Uniform Interface:
- Resource-Based: Individual resources are signified in requests. For example API or users.
- Manipulation of Resources via Representations: The client has a representation of the resource and it comprises sufficient information to change or delete the resource on the server.
- Self-descriptive Messages: Every message comprises sufficient information to describe how to process the message. Therefore, that server may easily analyze the request.
- Hypermedia as the Engine of Application State (HATEOAS): It requires adding links for each response. Therefore, that client may discover other resources easily.
This constraint basically means that client applications and server applications MUST be capable to develop gradually without any dependency on each other. A client should understand only resource URIs, and that’s all. Nowadays, this is standard practice in web development. Therefore, nothing fancy is needed from our side. Keep it easy.
Stateless means that the required state to control the request is contained within the request itself. The server will not keep anything related to the session. The client must contain all information for the server. That is to fulfill the request whether as a part of query params, headers, or URI in REST. Statelessness allows greater availability since the server does not have to communicate that session state. There is a setback when the client requires to send a lot of data to the server. Therefore, it decreases the scope of network optimization and needs more bandwidth.
There is on the World Wide Web, clients and intermediaries may cache responses. Responses must describe themselves implicitly or explicitly as either cacheable or non-cacheable to pause the clients from giving stale or inappropriate data in response to further requests. Well-organized caching partially or completely removes some client-server interactions. That is for further enhancing scalability and performance.
5. Layered system
REST introduces and enables us to use a layered system architecture where;
- We deploy the APIs on server A.
- Store data on server B.
- Authenticate requests in Server C.
For example. The client may not ordinarily tell whether it is linked directly to the end server or an intermediary along the way.
6. Code on demand (optional)
This is an optional constrain. Many times, we will be sending the static representations of resources in the form of XML or JSON. Though, when we require to, we are free to
return executable code support a part of our application. For example, clients can call our API to get a UI widget rendering code. It is allowed.
- All the above constraints help us to build a truly RESTful API.
- We should follow them.
- We can find ourselves violating one or two constraints.
- Do not worry; we are still making a RESTful API.
- All above-described constraints are most closely related to World Wide Web (WWW).
- Using RESTful APIs, we can do the same thing with our web services that we do to web pages.
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