Should Java POJOs Implement Field Validation and Throw Exceptions in Setter Methods?

Is it advisable to include field validation and exception handling in setter methods for Java POJOs?

In Java, Plain Old Java Objects (POJOs) are often used to represent data structures without business logic. However, it's a common subject of debate whether setters in POJOs should enforce validation and handle exceptions. This article discusses the implications of implementing such practices in your POJOs.

public class User {
    private String email;

    public void setEmail(String email) {
        if (email == null || !email.contains("@")) {
            throw new IllegalArgumentException("Email must not be null and must contain '@'.");
        }
        this.email = email;
    }
}

Causes

• Ensures data integrity by preventing invalid states in objects.
• Improves error handling by allowing immediate feedback for invalid inputs.
• Promotes maintainability through consistent validation across the application.

Solutions

• Implement validation checks within setter methods to ensure that any data assigned to fields meets required criteria.
• Use custom exceptions to provide detailed error messages in case of validation failures.
• Consider using Java Bean Validation (JSR 380) for declarative and reusable validation annotations.

Mistake: Not throwing exceptions on invalid data, leading to silent failures.

Solution: Always throw a clear and informative exception when data validation fails.

Mistake: Overcomplicating setter methods with too much business logic.

Solution: Keep setter methods concise; if complex logic is needed, extract it to a service class.