![]() If the response is cacheable, the client application gets the right to reuse the response data later for equivalent requests and a specified period. The cacheable constraint requires that a response should implicitly or explicitly label itself as cacheable or non-cacheable. The server cannot take advantage of any previously stored context information on the server.įor this reason, the client application must entirely keep the session state. Statelessness mandates that each request from the client to the server must contain all of the information necessary to understand and complete the request. ![]() While the client and the server evolve, we have to make sure that the interface/contract between the client and the server does not break. The client-server design pattern enforces the separation of concerns, which helps the client and the server components evolve independently.īy separating the user interface concerns (client) from the data storage concerns (server), we improve the portability of the user interface across multiple platforms and improve scalability by simplifying the server components. The client application should dynamically drive all other resources and interactions with the use of hyperlinks. ![]() Hypermedia as the engine of application state – The client should have only the initial URI of the application.It should also provide information of the additional actions that the client can perform on the resource. Self-descriptive messages – Each resource representation should carry enough information to describe how to process the message.API consumers should use these representations to modify the resources state in the server. Manipulation of resources through representations – The resources should have uniform representations in the server response.Identification of resources – The interface must uniquely identify each resource involved in the interaction between the client and the server.The following four constraints can achieve a uniform REST interface: Multiple architectural constraints help in obtaining a uniform interface and guiding the behavior of components. Uniform Interfaceīy applying the principle of generality to the components interface, we can simplify the overall system architecture and improve the visibility of interactions. ![]() The six guiding principles or constraints of the RESTful architecture are: 1.1. These principles must be satisfied if a service interface needs to be referred to as RESTful.Ī Web API (or Web Service) conforming to the REST architectural style is a REST API. Like other architectural styles, REST has its guiding principles and constraints. Roy Fielding first presented it in 2000 in his famous dissertation. Extension is discussed later in this section.REST is an acronym for REpresentational State Transfer and an architectural style for distributed hypermedia systems. Interfaces cannot be instantiated-they can only be implemented by classes or extended by other interfaces. Method bodies exist only for default methods and static methods. In the Java programming language, an interface is a reference type, similar to a class, that can contain only constants, method signatures, default methods, static methods, and nested types. In fact, each group considers its software highly proprietary and reserves the right to modify it at any time, as long as it continues to adhere to the published interface. Neither industrial group needs to know how the other group's software is implemented. The guidance manufacturers can then write software that invokes the methods described in the interface to command the car. The auto manufacturers must publish an industry-standard interface that spells out in detail what methods can be invoked to make the car move (any car, from any manufacturer). Another industrial group, electronic guidance instrument manufacturers, make computer systems that receive GPS (Global Positioning System) position data and wireless transmission of traffic conditions and use that information to drive the car. Automobile manufacturers write software (Java, of course) that operates the automobile-stop, start, accelerate, turn left, and so forth. Generally speaking, interfaces are such contracts.įor example, imagine a futuristic society where computer-controlled robotic cars transport passengers through city streets without a human operator. Each group should be able to write their code without any knowledge of how the other group's code is written. There are a number of situations in software engineering when it is important for disparate groups of programmers to agree to a "contract" that spells out how their software interacts.
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