Hey there! If you build technology products these days, you have likely heard the letters "API" thrown around a lot. APIs allow different applications to talk to one another by formally defining how one system can request services and data from another in a structured way.
As an API developer, you have choices in how your API communicates behind the scenes using particular sets of standards and design paradigms. The two major styles for API development are known as SOAP and REST. They take fundamentally different approaches.
Throughout this guide, we will unpack the meaning behind these buzzwords to understand how SOAP and REST differ, probe their technical trade-offs, and identify which situations each one handles best. Like choosing between taking the highway or scenic backroads to reach your destination, SOAP and REST can both work – the optimal path depends on your specific needs.
Let‘s shift gears and start unraveling what makes them unique!
Under the Hood: SOAP vs REST Architectural Styles
Inside SOAP: Remote Procedure Calls
The SOAP style stands for Simple Object Access Protocol. It relies on the concept of Remote Procedure Calls (RPCs) – packaging up requests to execute functions hosted remotely as if they were local procedures inside your own program.
For example, imagine we have a separate AirportWeatherReporting server that checks conditions. My client application could access its functionality using RPCs like this:
getWeatherReport(airportCode)
fetchWeatherForecast(dateRange)Rather than directly executing my own weather reporting logic locally, SOAP offloads these functions calls to a remote server in a standardized XML structure.
This RPC abstraction however means both my client and the server have to strictly adhere to predefined interfaces specifying the inputs, outputs, error codes etc. I couldn‘t suddenly call checkWeather() for instance without the server throwing an error!
Inside REST: Resources and Representations
REST stands for Representational State Transfer and is more loosely coupled. It treats servers as black boxes that expose resources which clients interact with.
These resources correspond to nouns like /airport, /forecast, /observations. The verbs come from HTTP request types – GET, POST, PUT, DELETE etc.
GET /observations/lax
PUT /forecasts/2023-03-01Resources return representations – payload data formatted in HTML, JSON, XML, images etc. REST cares only about the media types, not rigid method call structures.
Thisremoves the tight coupling seen in RPC-based SOAP. Server and client teams can work independently and evolve functionality as long as resources remain identifiable.
Communication Protocols and Message Encodings
SOAP and REST adopt different styles when it comes to protocols used for communication and data formats for message encoding as well:
| SOAP | REST | |
|---|---|---|
| Protocols | HTTP, SMTP, TCP, JMS | Only HTTP |
| Data Formats | XML | XML, JSON, Plain Text, HTML |
SOAP‘s Protocol and Payload Flexibility
A core design goal of SOAP was creating a messaging framework versatile enough to work across many transport protocols – enabling programs on diverse platforms to communicate.
This explains SOAP‘s wide protocol support – HTTP, SMTP, even proprietary middleware like Java Messaging Service (JMS). The mandatory XML format (hence Simple XML Access Protocol!) similarly aimed for broad accessibility across languages and technologies.
However, while versatile, XML brings overhead. Verbose syntax and expensive parsing affects SOAP performance.
REST + HTTP + JSON = BFFs
Contrast this to REST‘s constraints – communication must use HTTP requests between components. This inherent binding to web infrastructure explains REST‘s immense popularity for creating web APIs accessed by browsers today.
Thanks to resting upon HTTP, REST allows tapping into caching, encryption, compression and other useful features for free!
Additionally, REST permits flexibility in message payloads – XML but increasingly JSON thanks to its lightness and JavaScript interoperability. JSON parsing is also faster and less resource intensive relative to XML – a boon for performance.
Together, HTTP+JSON unlock simplicity, scalability and speed advantages for REST APIs.
Caching Support: Built-in Wins for REST
Speaking of performance boosters, let‘s explore another area where REST APIs enjoy an advantage – leveraging caches.
temporaryase data in a cache avoids expensive regeneration or refetches from slow backends – wins for speed and efficiency! While possible to manually code caching into SOAP services, REST inherently enables this thanks to underlying HTTP.
Frameworks like Express in Node.js for building REST apps even support hooks to quickly plug in cache layers like Redis. This baked-in leverage allows REST services to comfortably scale up throughput. SOAP needs extra effort to match.
Security Showdown: WS-Security vs SSL+HTTPS
Since APIs often ferry sensitive information, security is a vital consideration when evaluating protocols. Both SOAP and REST offer risk mitigation capabilities here:
| Security Mechanism | SOAP | REST |
|---|---|---|
| Encryption | WS-Security Standards | SSL/TLS |
| Authentication | WS-Security Tokens | API Keys |
| Data Integrity | Digital Signatures | Hashing |
SOAP‘s WS-Security specifications build in end-to-end safeguards like encryption, identity tokens and digital signatures for verifying payloads haven‘t been tampered with in transit. Powerful but complex to configure.
In REST, prevalent options include HTTPS encryption via SSL/TLS certificates and API key-based authentication hardcoded into requests – easy to implement by developers. For integrity, hashing algorithms like SHA or MD5 suffice in most common cases.
While advanced needs benefit from WS-Security, REST‘s security tooling meets typical app needs with its simplicity.
API Development Frameworks and Tooling
Developer experience selecting either style impacts productivity. Let‘s compare popular tooling available in both ecosystems:
| SOAP Frameworks | REST Frameworks | |
|---|---|---|
| Languages | Java, .NET, C++ | JavaScript, Ruby, Python, PHP |
| Examples | Apache Axis2, Oracle WebLogic | Express, Django REST, Flask |
| Features | WS-* standards support | Rapid prototyping |
| Testing | SoapUI | Postman, Frisby.js |
The SOAP ecosystem provides robust enterprise-grade frameworks like Apache Axis2 catering to Java and .NET highly popular in corporate environments. Testing tools like SoapUI also help test SOAP interfaces.
Meanwhile simple scripting languages dominate REST frameworks – Node.js, Python, Ruby etc thanks to developer velocity wins. Lightweight testing libraries assist rapid iteration.
Tooling trade-offs depend on existing tech skillsets and platform preferences.
Real-World API Usage Scenarios
We have explored SOAP and REST characteristics in depth. How do these architectural choices fare with real-world API use cases?
SOAP API Example Uses
Banking Systems – Mission-critical money transfers demand guaranteed delivery. WS-Security standards help by encrypting payloads end-to-end. Related financial protocols build atop SOAP.
Telecom Systems – Telco network infrastructure relies on legacy C++ systems communicating via SOAP interfaces internally thanks to wide platform support.
Enterprise Middleware – SOAP‘s verbosity aids machine readability. Thus SOAP intermediates disparate systems across departments pixie HR, payroll, CRM etc.
Travel Industry – Public travel APIs use XML payloads for rich data structuring – flight+hotel bundles require nesting.
REST API Example Uses
Mobile Applications – Native iOS/Android apps use REST to fetch data from servers. JS interop drives REST adoption.
Web Applications – Browser apps communicate to backends predominantly via REST thanks to its cacheability DNA.
Microservices Architectures – Decentralized microservices mesh well with REST‘s modular style – granular APIs for each service.
Public Cloud Services – AWS, GCP, Azure expose REST management interfaces – easy to call from any language.
In summary, SOAP prevails in enterprise, legacy and transactions domains where reliability trumps raw speed thanks to robust tooling. REST dominates in the internet sphere powering apps targeting scale.
Making Your API Architecture Decision
We have covered a lot comparing these two approaches! Let‘s conclude by crystallizing guidance on when to choose which according to app needs:
When to use SOAP:
- Strict formal data contracts required
- Advanced security features needed end-to-end
- Guaranteed transactions for reliability
- Enterprise integration with existing systems
- Preferred languages like Java and .NET
When to use REST:
- Web/Internet user base
- Need for scale and performance
- Rapid experimentation required
- JavaScipt/mobile clients
- Public API consumption
As observed, there are situational benefits for either paradigm. The sweet spot for SOAP remains enterprise use within controlled environments. REST dominates for outward-facing APIs.
Hopefully you feel empowered navigating this decision for your next API adventure! Please drop me a note if you have any other questions.
