SOAP API and REST API

SOAP API and REST API are two commonly used API's to expose your data from force.com platform to the other platforms(JAVA , .NET ,etc) or to allow external application to invoke Apex methods.

What is SOAP ?

The Simple Object Access Protocol (SOAP) is an attempt to define a standard for creating web service APIs. It is a pattern, a web service architecture, which specifies the basic rules to be considered while designing web service platforms. It typically uses HTTP as a layer 7 protocol, although this is not mandatory. The SOAP message itself consists of an envelope, inside of which are the SOAP headers and body, the actual information we want to send. It is based on the standard XML format, designed especially to transport and store structured data. SOAP may also refer to the format of the XML that the envelope uses.
SOAP is a mature standard and is heavily used in many systems, but it does not use many of the functionality build in HTTP. While some consider it slow, it provides a heavy set of functionality which is a necessity in many cases. It might now be the best solution for browser-based clients, due to its custom format.

 What is REST ?

The Representational State Transfer (REST) is another architectural pattern (resource-oriented), an alternative to SOAP. Unlike SOAP, RESTful applications use the HTTP build-in headers (with a variety of media-types) to carry meta information and use the GET, POST, PUT and DELETE verbs to perform CRUD operations. REST is resource-oriented and uses clean URLs (or RESTful URLs).

For example :
http://www.developingthefuture.com/index.php?page=foo
becomes
http://www.developingthefuture.com/foo

This kind of URLs syntax greatly improves both visibility and usability. It doesn’t use any query strings, and it also provides certain SEO benefits (the crawlers just love plain text). The body of the REST message can be XML, JSON or any other format, although JSON is usually the preferred choice. On the other hand, you can’t use JSON with SOAP. Or at least not entirely, because SOAP uses XML by definition for it’s envelope. It should also mentioned that REST is, by design, protocol-agnostic, although it is usually used with HTTP.

SOAP API

1)Supports data in the form of XML only 2)Requires WSDL for the integration 3)Use SOAP API in any language that supports Web services.

REST API

1)Supports both XML and JSON format 2)Preferred for mobile and web apps since JSON being Lighter the app runs smoother and faster

***************** Few Important Questions on SOAP & REST **********************

1.What is SOAP and What is REST?

REST API

Representational State Transfer.
It is based URI
It works with GET,POST,PUT,DELETE
Works Over with HTTP and HTTPS


SOAP API

Simple Object Access Protocol.
It is based on Standard XML format
It is works with WSDL
Works Over with HTTP,HTTPS,SMPT,XMPP


2.Difference between REST API and SOAP API?
Ans :Varies on records that can be handled. Generally if we want to access less number of records we go for REST API.

3.What is WSDL?
A WSDL is an XML Document which contains a standardized description of how to communicate using webservice.

4.What are the different type of WSDL'S?
Ans:
Enterprise WSDL
Partner WSDL
Apex WSDL
Metadata WSDL
Tooling WSDL
Delegated Atuntection WSDL

5.Difference between Enterprise WSDL and Partner WSDL?
Ans:
Enterprise WSDL:
It is used for building client applications for a single salesforce organization.
Customers who use enterprise WSDL document must download and re-consume it when ever their organization makes a change to its custom objects or fields or when ever they want to use a different version of the API.
Partner WSDL:
It is used for building client applications for multiple organizations.
The partner WSDL documention only needs to be downloaded consumed once per version of the API.

6.How can you expose an apex class as a REST web service in salesforce?
Ans - An apex class can be exposed as REST web service by using keyword '@RestResource'

7.How to fetch data from another Salesforce instance using API?
Ans :Use the Force.com Web Services API or Bulk API to transfer data We this this is a great job for the Bulk API.

8.How to call Apex method from a Custom Button?
Ans :An Apex callout enables you to tightly integrate your Apex with an external service by making a call to an external Web service or sending a HTTP request from Apex code and then receiving the response.
Apex provides integration with Web services that utilize SOAP and WSDL, or HTTP services (RESTful services).

9.What is the use of Chatter REST API?
The Chatter API (also called Chatter REST API) lets you access Chatter information via an optimized REST-based API accessible from any platform. Developers can now build social applications for mobile devices, or highly interactive websites, quickly and efficiently.

10.How to fetch data from another Salesforce instance using API?
Answer: Use the FORCE.COM WEB SERVICES API or BULK API to transfer data We this this is a great job for the Bulk API.

11.What are callouts and call ins?
Making a request to an external system from salsforce is callout.

Getting requests from an external system is a call in.

12.How many callouts to external service can be made in a single apex transaction?
Ans - A total of 10 callouts are allowed in a single apex transaction.

13.What is the maximum allowed time limit while making a callout to external service in apex?
Ans - maximum of 120 second time limit is enforced while making callout to external service

14.What is the default timeout period while calling webservice from Apex.
Ans : 10 sec.

15.can we define custom time out for each call out?
Ans :
A custom time time can be defined for each callout.
the minimum time is 1 millisecond and maximum is 120,000 milli seconds.

16.How to increase timeout while calling web service from Apex ?
Ans :
docSample.DocSamplePort stub = new docSample.DocSamplePort();

stub.timeout_x = 2000; // timeout in milliseconds