Salesforce Apex Annotations

@AuraEnabled

Purpose: Makes a method accessible from a Lightning component.

Example:

public class MyController {
    @AuraEnabled
    public static String sayHello(String name) {
        return 'Hello ' + name;
    }
}

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@Deprecated

Purpose: Indicates that a method or class should no longer be used.

Example:

public class OldClass {
    @Deprecated
    public static void oldMethod() {
        // Old implementation
    }
}

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@Future

Purpose: Marks a method that runs asynchronously.

Example:

public class AsyncProcessor {
    @Future
    public static void processAsync() {
        // Asynchronous processing
    }
}
@InvocableMethod

Purpose: Allows a method to be called from a Process Builder or Flow.
Example:
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public class FlowController {
    @InvocableMethod
    public static void processRecords(List<Id> recordIds) {
        // Process logic
    }
}

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@InvocableVariable

Purpose: Used within a class that has @InvocableMethod to define variables that can be set from a Flow or Process Builder.

Example:

public class Parameters {
    @InvocableVariable
    public String param1;
}

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@IsTest

Purpose: Marks a class or method as a test class or test method.

Example:

@IsTest
private class TestMyClass {
    @IsTest static void testMyMethod() {
        // Test code
    }
}

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@JsonAccess

Purpose: Allows non-public members of Apex classes to be serialized and deserialized in JSON.

Example:

public class MyClass {
    @JsonAccess
    private String myField;
}

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@NamespaceAccessible

Purpose: Exposes a global class, method, or variable to any Apex code that resides in a namespace.

Example:

@NamespaceAccessible
public class SharedClass {
    // Class implementation
}

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@ReadOnly

Purpose: Allows a Visualforce page to perform read-only operations that do not count against the governor limits for SOQL queries.

Example:

@ReadOnly
public with sharing class MyReadOnlyClass {
    // Query logic
}

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@RemoteAction

Purpose: Exposes a method in a Visualforce controller to be called from JavaScript.

Example:

public with sharing class MyController {
    @RemoteAction
    public static String performAction(String param) {
        // Action logic
    }
}

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@SuppressWarnings

Purpose: Instructs the compiler to suppress specific warnings.

Example:

@SuppressWarnings('deprecation')
public class MySuppressedClass {
    // Code that uses deprecated methods
}

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@TestSetup

Purpose: Used in test classes to define methods that set up test data.

Example:

@IsTest
private class MyTestClass {
    @TestSetup
    static void setup() {
        // Setup test data
    }
}

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@TestVisible

Purpose: Allows test methods to access private or protected members of another class.

Example:

public class MyClass {
    @TestVisible private static Integer myCounter = 0;
}

Each of these annotations serves a specific purpose and helps define the behavior of your Apex code in different scenarios, particularly in the context of Salesforce's multi-tenant environment and its governor limits.