Setting default values for columns in JPA

Strive for consistency in multi-application environments

In scenarios where multiple applications are interacting with the same database, it's paramount to maintain data integrity and consistency. Although application-level defaults seem desirable, they won't be universally respected by all applications. Thus, database-level defaults become a more reliable option via the columnDefinition attribute of @Column.

Prioritize database integrity with @PrePersist

To set defaults based on complex business logic which cannot be expressed through a constant, use the @PrePersist method. This runs just before the entity is persisted, cleverly preventing any existing values from being overwritten.

@PrePersist
public void preInsert() {
    if (this.someValue == null) { 
        this.someValue = calculateDefaultValue(); 
    }
}
// The method name "preInsert" is clearly more fancy than "onInsert"
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Use of field-level defaults vs. the @PrePersist

Setting a field with a default value during its declaration is the most intuitive and simplest way to define a default value.

public class DefaultEntity {
    private String defaultAttitude = "Relaxed";
    // Cause who needs stress am I right?
    // ...
}
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There could be scenarios where @PrePersist may come handy:

• The default value depends on the evaluation of other properties.
• Defaults depending on a runtime computation, or response from external services.
• Situations where the default should refrain from overriding a null value already set.

Each strategy caters to a precise need, so choose wisely according to your specific use case.

Emphasize clarity with intuitive @PrePersist method names

Endeavor to name @PrePersist methods intuitively, such as preInsert, to enhance their self-explanatory nature and promote code readability. Clear method naming contributes substantially to code maintainability, besides being an absolute treat for the hapless developer who inherits your code!