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"@Scheduled" Annotation Should Only Be Applied to No-Arg Methods

High
correctnessmaintainability

What is it?​

This practice targets methods in Java Spring applications annotated with @Scheduled that incorrectly use method arguments, which can lead to runtime errors.

Why apply it?​

According to Spring documentation, the @Scheduled annotation should only be applied to no-argument methods. Violating this can result in runtime errors, which affects the reliability of the application.

How to fix it?​

Transform any method annotated with @Scheduled to a no-argument method to avoid runtime errors and ensure compliance with Spring's guidelines.

Examples​

Example 1:​

Negative​

The negative example incorrectly adds a parameter to a method meant for @Scheduled, which will not execute properly.

public class IncorrectScheduledService {

    @Scheduled(fixedRate = 10000)
    public void processFiles(String directoryPath) { /* Noncompliant */
        System.out.println("Processing files in directory: " + directoryPath);
        // Logic for file processing
    }

    private void helperMethod(String directoryPath) {
        // Helper logic using the directory path
    }
}

Example 2:​

Positive​

The positive example transforms a scheduled task into a no-argument method, ensuring it will run without errors.

public class PositiveExampleService {

    @Scheduled(cron = "0 0 * * * ?")
    public void scheduledTask() { /* Compliant */
        System.out.println("Performing scheduled task...");
        // Other task implementation logic
    }

    public void otherMethod() {
        // Method logic that might involve parameters
    }
}

Negative​

The negative example demonstrates an incorrect usage of @Scheduled with a method that includes arguments, leading to runtime issues.

public class NegativeExampleService {

    @Scheduled(cron = "0 0 * * * ?")
    public void scheduledTask(String param) { /* Noncompliant */
        System.out.println("Scheduled task with param: " + param);
        // Task implementation
    }
    
    public void otherMethod(String param) {
        // Method logic involving the parameter
    }
}

Example 3:​

Positive​

This positive example shows another correct application of a no-arg method for a fixed rate scheduled task.

public class CorrectScheduledService {

    @Scheduled(fixedRate = 10000)
    public void processFiles() { /* Compliant */
        System.out.println("Processing files at fixed rate...");
        // Logic for file processing
    }

    private void helperMethod() {
        // Helper logic if needed
    }
}