Asyncronous Apex

Asynchronous apex is nothing but to run task or processes in a separate thread, at a later time. Without having user to wait for the task to finish.

The advantages of this approach are :

• High user efficiency
• High Scalability
• Increased Governor & Execution Limits

In short, you don't have to wait in a queue to wait for the task to finish and then execute the second task.

Types of Asynchronous Apex :

• Future Methods
• Queuable Jobs
• Scheduled Apex
• Batch Apex

When you want to use a future method in salesforce we use @future annotation.

Future annotation (@future) :

1. Use the future annotation to specify that these methods that are executed asynchronously.

2. Methods with future annotation must be static methods.

3. Methods with future annotation can only return a void type.

Let's have a look at the syntax :

============================================

global class classname

{

 @future 

static void methodname(parameters)

{

  //body of the method

 }

}

Future method callouts using @future(callout=true)

To allow callout from the future method annotation needs an extra parameter (callout=true) to indicate that callouts are allowed. Here is example

global class FutureMethodExample {     @future(callout=true)     public static void getStockQuotes(String acctName){         // Perform a callout to an external service     } } IMPORTANT NOTE : ·       No more than 10 method calls per Apex invocation ·       You cannot call a method annotated with the future from a method that also has the future annotation, nor you can call trigger from an annotated method that calls another annotated method. ·       All asynchronous calls made after the startTest method are collected by the system. When stopTest is executed, all asynchronous processes are run synchronously. ·       Use when you want to avoid DML exception. ·       It is used for higher governor limits. ·       To avoid mixed DML exception.   LIMITATION : ·       No more than 25 lakh Jobs/24 hrs ·       No more than 50 method calls per apex. ·       One future method cannot call another future method. BEST PRACTICE OF FUTURE METHODS : ·       Do not call future methods inside for loops. ·       Avoid complex calculations in future methods, else use batch apex. ·       Always consider @future limit is equal to 2x SOQL query.