Soap vs Rest | Know Their Differences and Which Should You Learn?
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Soap vs Rest | Know Their Differences and Which Should You Learn?

Last updated on 26th Dec 2021, Blog, General

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Ravichandran (Data Engineer - Financial Performance and Analytics )

Ravichandran has a wealth of experience in cloud computing, BI, Perl, Salesforce, Microstrategy, and Cobit. Moreover, he has over 9 years of experience as a data engineer, financial performance, and analytics.

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SOAP stands for Simple Object Access Protocol whereas REST stands for Representational State Transfer. SOAP needs more bandwidth for its usage whereas REST doesn’t need much bandwidth. Comparing SOAP vs REST API, SOAP only works with XML formats whereas REST work with plain text, XML, HTML and JSON.

    • What is SOAP?
    • What is REST?
    • Key Differences
    • Difference Between SOAP and REST
    • When to use REST?
    • Challenges in SOAP API
    • Advantage of SOAP and Rest
    • Features of SOAP and Rest
    • Conclusion

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      What is SOAP?

      SOAP is a protocol that was designed before REST and came into the picture. The main idea behind designing SOAP was to ensure that programs built on different platforms and programming languages ​​can exchange data in an easy way. SOAP stands for Simple Object Access Protocol.

      SOAP: Simple Object Access ProtocolSOAP is a standard protocol that was first designed so that applications built in different languages and on different platforms can communicate. Because it is a protocol, it implements built-in rules that increase its complexity and overhead, which can lead to longer page load times. However, these standards also provide built-in compliance that can make it better suited for enterprise scenarios. Underlying compliance standards include security, atomicity, consistency, isolation and durability (ACID), a set of properties to ensure reliable database transactions.


      Common web service specifications include:

      Web Service Security (WS-Security): Standardised how messages are secured and transferred via unique identifiers called tokens.

      WS-ReliableMessaging: Standardised error handling between messages transferred across untrusted IT infrastructure.

      Web services addressing (WS-addressing): Instead of maintaining such information deep within the network, SOAP packages the information as metadata within headers.

      Web Service Description Language (WSDL): Describes what a web service does, and where that service starts and ends.

      When a request for data is sent to the SOAP API, it can be handled via any of the application layer protocols: HTTP (for web browsers), SMTP (for email), TCP, and others. However, once the request is received, the return SOAP messages must be returned as XML documents—a markup language that is both human- and machine-readable. A completed request to a SOAP API is not cacheable by the browser, so it cannot be accessed later without sending it to the API.


      What is REST?

      REST is a set of architectural principles tailored to the needs of lightweight web services and mobile applications. Since this is a set of guidelines, it leaves the implementation of these recommendations to the developers.

      When a request for data is sent to a REST API, it is usually done via Hypertext Transfer Protocol (commonly referred to as HTTP). Once the request is received, APIs designed for REST (called RESTful APIs or RESTful web services) can return messages in a variety of formats: HTML, XML, plain text, and JSON. JSON (JavaScript Object Notation) is preferred as a messaging format because it can be read by any programming language (despite the name), is human- and machine-readable, and is lightweight. In this way, RESTful APIs are more flexible and can be easier to set up.


      An application is said to be RESTful if it follows the 6 Vastu guidelines. A reliable application should have:

    • Client-server architecture composed of clients, servers and resources.
    • Stateless client-server communication, which means that no client content is stored on the server between requests. Instead information about the state of the session remains with the client.
    • Cacheable data to eliminate the need for some client-server interaction.

    • Uniform interface between components so that information can be transferred in a standardised form rather than specific to the needs of an application. It has been described by Roy Fielding, the originator of REST, as “the central feature that differentiates the REST architectural style from other network-based styles.”
    • A layered system constraint, where client-server interactions can be mediated by hierarchical layers.
    • Code on Demand allows the server to extend the functionality of the client by moving the executable code (though reducing visibility, making this an optional guideline).
    • REST was specifically designed to work with components such as media components, files or even objects on a particular hardware device. Any web service which is defined on the principles of REST can be called as RESTful web service. A rest service will use the common HTTP verbs of GET, POST, PUT and DELETE to work with the required components. REST stands for Representational State Transfer.

      Key Differences:

    • SOAP stands for Simple Object Access Protocol while REST stands for Representational State Transfer.
    • SOAP is a protocol whereas REST is an architectural pattern.
    • SOAP uses service interfaces to expose its functionality to client applications whereas REST uses Uniform Service Locators to access components on hardware devices.
    • SOAP requires more bandwidth for its use whereas REST does not require much bandwidth.
    • Comparing SOAP vs REST API, SOAP only works with XML formats whereas REST works with plain text, XML, HTML and JSON.
    • SOAP cannot use REST whereas REST can use SOAP.

      Difference Between SOAP and REST:

    • Many legacy systems may still follow SOAP, while REST came later and is often seen as a faster alternative in web-based scenarios. REST is a set of guidelines that provide flexible implementation, whereas SOAP is a protocol with specific requirements such as XML messaging.

    • REST APIs are lightweight, making them ideal for new contexts such as Internet of Things (IoT), mobile application development and serverless computing. SOAP web services provide built-in security and transaction compliance that aligns with many enterprise needs, but it also makes them bulky. Additionally, many public APIs, such as the Google Maps API, follow the REST guidelines.

    • Each technology has its advantages and disadvantages. Therefore, it is always good to understand in which situations each design should be used. This REST and SOAP API difference tutorial covers some of the key differences between REST and SOAP APIs, as well as what challenges you might face while using them.

    • Below is the main difference between SOAP and REST API:

    • SOAP stands for Simple Object Access Protocol.
    • REST stands for Representational State Transfer.
    • SOAP is a protocol. SOAP was designed with a specification in mind. It includes a WSDL file that contains essential information about what the web service does in addition to the location of the web service.
    • REST is an architectural style in which a web service can be considered as a RESTful service only if it adheres to the constraints of being client server,stateless,collectible,layered system, uniform interface.
    • SOAP cannot use REST because SOAP is a protocol and REST is an architectural pattern.
    • REST can use SOAP as the underlying protocol for web services, because in the end it is just an architectural pattern.
    • SOAP uses service interfaces to expose its functionality to client applications. In SOAP, the WSDL file provides essential information to the client that can be used to understand what services a web service can offer.
    • REST uses Uniform Service Locators to access components on a hardware device. For example, if there is an object that represents the data of an employee hosted at , below are some URIs that may exist to access them.
    • SOAP requires more bandwidth for its use. Since SOAP messages contain a lot of information inside it, the amount of data transfer using SOAP is usually very high.

    • REST does not require much bandwidth when the request is sent to the server. REST messages consist mostly of JSON messages. Below is an example of a JSON message passed to a web server. You can see that the message size is comparatively smaller than SOAP. {“city”: “Mumbai”, “state”: “Maharashtra”}. SOAP can only work with XML format. As seen from SOAP messages, all the data passed is in XML format.


      When to use REST?

      One of the most debatable topics is when REST should be used or when to use SOAP when designing web services. Below are some of the major factors that determine when REST and SOAP API technology should be used for web services REST services should be used in the following examples:

      Limited resources and bandwidth – Since SOAP messages are heavy in content and consume more bandwidth, REST should be used in cases where network bandwidth is a bottleneck.


      Statelessness – REST should be used if there is no need to maintain the state of information from one request to another. If you need a proper information flow in which some information needs to flow from one request to another then SOAP is more suitable for that purpose. We can take the example of any online shopping site. These sites usually require the user to add the items they need to purchase to the cart. All cart items are transferred to the payment page to complete the purchase. This is an example of an application that needs a state feature. The status of the cart item needs to be transferred to the payment page for further processing.


      Caching – If a lot of requests need to be cached then REST is the right solution. At times, clients may request multiple times for the same resource. This can increase the number of requests sent to the server. By implementing a cache, the results of the most frequent queries can be stored in an intermediate location. So whenever the client makes a request for a resource, it will first check the cache. If the resource exists, it will not proceed to the server. Therefore caching can help in reducing the amount of visits that have to be done to the web server.


      Ease of Coding – The coding and subsequent implementation of REST services is far easier than that of SOAP. So if a quick win solution is needed for web services, REST is the way to go.


      When to use SOAP?

      Asynchronous Processing and Subsequent Invocation – If the requirement is that the client requires a guaranteed level of reliability and security then the new SOAP standard of SOAP 1.2 provides a lot of additional features, especially when it comes to security.


      A formal means of communication – SOAP 1.2 lays out strict specifications for this type of interaction if there is an agreement on the exchange format between both the client and the server. An example is an online shopping site in which users add items to a cart before a payment is made. Let’s say we have a web service that makes final payment. There can be a firm agreement that the web service will only accept the cart item name, unit price and quantity. If such a scenario exists, it is always better to use SOAP protocol.


      Stateful Operations – If the application requires that state needs to be maintained from one request to another, the SOAP 1.2 standard provides a WS* structure to support such requirements.


      Challenges in SOAP API:

      APIs are known as Application Programming Interfaces and are offered by both the client and the server. In the client world, it is offered by the browser whereas in the server world it is provided by a web service which can be either SOAP or REST.


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      Challenges with SOAP API

      WSDL file – One of the major challenges of the SOAP API is the WSDL document itself. The WSDL document is what tells the client about all the operations that can be performed by the web service. The WSDL document will contain all the information such as the data type being used in the SOAP messages and whether all the operations are available through the web service. The code snippet below is a part of a sample WSDL file.

    • As per the above WSDL file, we have an element named “TutorialName” which is of type String which element is part of TutorialNameRequest.

    • Now, suppose the WSDL file has to be changed as per the business requirements and TutorialName is to become TutorialDescription. This would mean that all clients that are currently connecting to this web service would need to make this related change in their code to accommodate the change in the WSDL file.

    • This illustrates the biggest challenge of the WSDL file which is the tight contract between the client and the server and that one change can have a major impact on the entire client application.

    • Document size – The other major challenge is the size of SOAP messages that are transferred from the client to the server. Using SOAP can be a big issue where bandwidth is a bottleneck, due to large messages.

      Challenges in REST API:

      Lack of security – REST does not impose any kind of security like SOAP. This is why REST is so well suited for publicly available URLs, but when it comes to passing confidential data between client and server, REST is the worst arrangement used for web services.


      State constraints – A stateful mechanism is required for most web applications. For example, if you had a shopping site that provided for having a shopping cart, it is necessary to know the number of items in the shopping cart before the actual purchase can be made. Unfortunately, the burden of maintaining this state lies with the client, which makes client applications bulky and difficult to maintain.


      Advantage of SOAP and Rest:

      Benefits of SOAP

      SOAP provides the following advantages over REST:

    • Language, platform and transport independent (REST requires the use of HTTP)
    • Works well in distributed enterprise environments (REST assumes direct point-to-point communication)
    • Standardised
    • Provides significant pre-build extensibility in the form of WS* standards
    • Built-in error handling
    • Automation when used with certain language products

    • Rest profit

      For the most part REST is easier to use and more flexible. It has the following advantages over SOAP:

    • No expensive tools are required to interact with the web service
    • Short learning curve
    • Efficient (SOAP uses XML for all messages, REST can use shorter message formats)
    • Fast (does not require extensive processing)
    • Closer to other web technologies in design philosophy

      Features of SOAP and Rest:

    • SOAP is a completely XML-based protocol, the data formatting is in XML so it is easy for the programmer to understand.
    • It is a platform independent protocol.
    • It is an open standard protocol so anyone can use it.
    • It is an extension of the HTTP protocol for XML messaging.
    • SOAP messaging is useful for transmitting messages from one computer to another.
    • It is also possible to implement a client-server architecture. The client can invoke a remote procedure call located on the server-side using SOAP protocol messaging.
    • SOAP provides data transport for web services.
    • SOAP works by sending an envelope that contains information about what needs to be done with web services. A typical SOAP envelope consists of a WSDL (Web Service Definition Language) file along with a header and body. This entire envelope is sent to the service provider and hence SOAP requires large bandwidth.

    • Features of Rest:

    • These are fast web services as they consume less bandwidth and resources.
    • REST can be written in any programming language.
    • These services can be executed on any platform.
    • It is a lightweight and scalable service built on the REST architecture.
    • It uses HTTP verbs like GET, POST, DELETE, PUT and PATCH for CRUD (Create, Read, Update and Delete) operations.
    • It supports basic communication encryption via TLS (Transport Layer Security), so is less secure than SOAP.
    • It is easy to develop.
    • It requires less bandwidth than SOAP.

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      Conclusion:

      We discussed the two most popular web services SOAP and REST. Both have their own importance in different scenarios. We have to choose any one of them based on our requirements and the complexity of the application. REST is easy to develop but on the other hand SOAP provides many other options so it is a bit difficult to develop


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