Annotations in salesforce

Annotations are defined with an initial
@

 symbol, followed by the appropriate keyword. To add an annotation to a method, specify it immediately before the method or class definition.

Apex supports the following annotations:

S.No	Apex Annotation Name	Description	Example
1	@isTest	Defines classes that only contain code used for testing your application. These classes don’t count against the total amount of Apex used by your organization.	@isTest private class MyTest { // Methods for testing }
2	@isTest( OnInstall=true)	Defines a test class or test method that executes on package installation	@isTest(OnInstall=true) private class TestClass { }
3	@isTest( SeeAllData=true)	Defines a test class or test method that has access to all data in the organization including pre-existing data that the test didn’t create. The default is false.	@isTest(SeeAllData=true) private class TestClass { }
4	@deprecated	Identifies methods, classes, exceptions, enums, interfaces, or variables that can no longer be referenced in subsequent releases of the managed package in which they reside	@deprecated public void limitedShelfLife() { }
5	@readOnly	Defines methods that can perform queries unrestricted by the number of returned rows limit for a request	@readOnly private void doQuery() { }
6	@remoteAction	Defines Apex controller methods that JavaScript code can call from a Visualforce page via JavaScript remoting. The method must be static and either public or global.	@remoteAction global static String getId( String s) { }
7	@restResource	Identifies a class that is available as a REST resource. The class must be global. The urlMapping parameter is your resource’s name and is relative to https://instance. salesforce.com/services/ apexrest/.	@restResource(urlMapping= ‘/Widget/*’) global with sharing class MyResource() { }
8	@httpGet, @httpPost, @httpPatch, @httpPut, @httpDelete	Defines a REST method in a class annotated with @restResource that the runtime invokes when a client sends an HTTP GET, POST, PATCH, PUT, or DELETE respectively. The methods defined with any of these annotations must be global and static.	@httpGet global static MyWidget__c doGet() { } @httpPost global static void doPost() { } @httpDelete global static void doDelete() { }
9	@future	Identifies methods that are executed asynchronously	global class MyFutureClass { @future static void myMethod( String a, Integer i) { System.debug( ‘Method called with: ‘ + a + ‘ and ‘ + i); // do callout, other long // running code } }