Web services are categorised into two types: SOAP and REST. Typically SOAP and REST are the methods used to call the web services. There are several differences between SOAP and REST. Firstly SOAP relies on XML to assist the services while REST can support various formats such as HTML, XML, JSON, etc. Another significant difference is that SOAP is a protocol. Conversely, REST is considered to be an architecture, which means that REST is a platform that uses existing protocols for the client and server interaction whereas SOAP itself a protocol through which client and server communicate.
Now, let’s understand what is a web service and why it is needed? Web service is an interface which a network accesses, to provide application functionality to the users. In other words, web service could be a service provided by one electronic device to other, interacting with each other. It contains three constituent part – first part involves a listener which receives messages, a proxy for fetching the message and converting it into the suitable action to be performed and for employing that particular action an application code is needed.
Content: SOAP Vs REST
|Basis for comparison||SOAP||REST|
|Expands to||Simple Object Access Protocol||Representational State Transfer|
|Basic||XML based message protocol utilizes WSDL.||Based on architecture and uses XML, JSON or other languages.|
|Size of the messages||Small||Larger as compared to SOAP.|
|Performance||Good||Better performance and caching support than SOAP.|
|Coupling between client and server||Tight coupling||Loose coupling|
|Security||Provide highly secure API||Less secure|
|Messaging protocols||HTTP, SMTP, FTP, TCP, etc.||HTTP protocol is used for transferring.|
|Invocation of services||Through RPC.||Uses URL.|
Definition of SOAP
SOAP (Simple Object Access Protocol) is the standard protocol designed for offering the web services to the consumers specifically for the message sharing. The specifications describe the rules used in transferring the information within the XML based envelope. These rules basically translate particular application and platform based data types into XML form. Several types of application messaging and integration formats implement SOAP design because of its appropriateness.
Message path and actors in SOAP
The exchange model describes that a message essentially involves a one-way transmission of an envelope from sender to the receiver but the fact is that it goes through many intermediary processes which have the ability to commit the change in terms of values or functionality. So, the combination of the intermediate web services along which a message flows is known as message path and the intermediary are referred to as an actor. There is a method named as “targeting” is used to recognise the number of actors involved in the processing of particular messages.
Features of SOAP
- SOAP depends on XML standards for the definition and function as SOAP is an application of XML specification.
- It uses two associated applications that are RPC and EDI. RPC provides a mechanism for making the procedure calls form one program to another in the distributed computing. EDI specifies a format and rendition of commercial documents and messages.
- SOAP messages involve an envelope which is comprised of an optional header and required body. The header information drives the processing of the message such as delivery, authentication, and transaction etc.
- Encoding style is a combination of rules for encoding the application and platform datatypes into regular XML syntax.
- For providing the information about communication errors occurring in the process, a special type of message SOAP fault message is utilized.
- WS-routing protocol is used in SOAP for the message routing.
- Transport protocols such as HTTP, FTP, SMTP, POP3, TCP, MQSeries and Jabber are used in SOAP which offers the capability to exchange SOAP messages.
Definition of REST
REST (Representational State Transfer) is an architectural approach constructed to operate best on the web. The REST web services describe certain restrictions to generate properties like performance, modifiability, scalability and allowing services. The major restriction that is implied in the REST is the uniformity in the interface. REST label the architectural approach, functionality and data as resources. To access these resources well-defined operations are performed on resources where the web links are used known as URIs (Uniform Resource Identifiers).
Another constraint on REST is that it needs the architecture to be client and server type and it is specifically designed for the exchange presentation of the resources utilizing uniform interface and protocol. Lastly, a stateless communication protocol is the standardized protocol to be used in the REST web services.
The primary advantage of using REST web services is that it is lightweight, simple and performs well as compared to SOAP. The REST uncovers all the functionalities of the RPC style service as used in SOAP, but rather than implementing it with custom named functions; it exposes resources that are mentioned above and comprised of standard HTTP objects. The crucial HTTP methods used for responding back in REST are: Create, Retrieve, Update and Delete. While in previous web services custom methods are used such as getobjects.
Key Differences Between SOAP and REST
- The SOAP essentially uses WSDL more specifically XML specification for its definition and function. On the other hand, REST can support formats, such as JSON, XML, etc.
- SOAP provides a standard and considered as a protocol while REST does not build new standards and uses existing standards as REST is just an architectural style.
- The size of the messages in REST is smaller and it also consumes less bandwidth because it just needs a JSON body with an HTTP connection for writing the request to the client, unlike SOAP. As against, SOAP contains large size messages which take a lot of bandwidth.
- The performance of REST is far better than SOAP and REST supports caching and banish the handling of XML envelope resulting minimized overhead.
- SOAP client and server are tightly coupled where any feature extension and alteration may not be possible or difficult. Conversely, in REST the client and server has a loose coupling and can easily adapt change.
- SOAP offers high security and is adhere to WS security specification while REST APIs are not that much secure and uses basic authentication and token-based mechanism.
- Only, HTTP is used in REST as the messaging protocol. On the contrary, SOAP could utilize protocols such as HTTP, SMTP, FTP, TCP for messaging.
- Services are invoked in the SOAP with the help of RPC method while in REST the services can also be called using URL.
SOAP is elected over REST when the machine to machine interaction, enterprise solutions and its security are the priority whereas REST is opted for the public facing lightweight APIs which can assist the CRUD operations.