Main differences between SOAP and RESTful web services in Java [duplicate]
REST is almost always going to be faster. The main advantage of SOAP is that it provides a mechanism for services to describe themselves to clients, and to advertise their existence.
REST is much more lightweight and can be implemented using almost any tool, leading to lower bandwidth and shorter learning curve. However, the clients have to know what to send and what to expect.
In general, When you're publishing an API to the outside world that is either complex or likely to change, SOAP will be more useful. Other than that, REST is usually the better option.
REST vs. SOAP Web Services
I am seeing a lot of new web services are implemented using a REST style architecture these days rather than a SOAP one. Lets step back a second and explain what REST is.
What is a REST web service?
The acronym REST stands for representational state transfer, and this basically means that each unique URL is a representation of some object. You can get the contents of that object using an HTTP GET, to delete it, you then might use a POST, PUT, or DELETE to modify the object (in practice most of the services use a POST for this).
Who's using REST?
All of Yahoo's web services use REST, including Flickr and Delicious.
APIs use it, pubsub, bloglines, Technorati, and both eBay, and Amazon have web services for both REST and SOAP.
Who's using SOAP?
Google seams to be consistent in implementing their web services to use SOAP, with the exception of Blogger, which uses XML-RPC. You will find SOAP web services in lots of enterprise software as well.
REST vs. SOAP
As you may have noticed the companies I mentioned that are using REST APIs haven't been around for very long, and their APIs came out this year mostly. So REST is definitely the trendy way to create a web service, if creating web services could ever be trendy (lets face it you use soap to wash, and you rest when your tired). The main advantages of REST web services are:
Lightweight - not a lot of extra XML markup Human Readable Results
Easy to build - no toolkits required. SOAP also has some advantages:
Easy to consume - sometimes Rigid - type checking, adheres to a contract Development tools For consuming web services, its sometimes a toss up between which is easier. For instance Google's AdWords web service is really hard to consume (in ColdFusion anyway), it uses SOAP headers, and a number of other things that make it kind of difficult. On the converse, Amazon's REST web service can sometimes be tricky to parse because it can be highly nested, and the result schema can vary quite a bit based on what you search for.
Whichever architecture you choose make sure its easy for developers to access it, and well documented.
SOAP
Simple Object Access Protocol (SOAP) is a standard, an XML language, defining a message architecture and message formats. It is used by Web services. It contains a description of the operations.
WSDL is an XML-based language for describing Web services and how to access them. It will run on SMTP, HTTP, FTP, etc. It requires middleware support and well-defined mechanism to define services like WSDL+XSD and WS-Policy.SOAP will return XML based data
REST
Representational State Transfer (RESTful) web services. They are second-generation Web services.
RESTful web services communicate via HTTP rather than SOAP-based services and do not require XML messages or WSDL service-API definitions. For REST middleware is not required, only HTTP support is needed. It is a WADL standard, REST can return XML, plain text, JSON, HTML, etc.