ID Resolution

Detection priority

Sprout searches the entity class for exactly one non-static field or getter method annotated with one of these, in order:

1. @de.flix29.sprout.annotations.SproutId
2. @jakarta.persistence.Id
3. @javax.persistence.Id

Rules:

• Exactly one ID element must be found. Zero or more than one causes a compilation error.
• Getter methods are considered only when they are non-static, have no parameters, and return a non-void type.
• @EmbeddedId is not supported and causes a compilation error.

What the resolved ID affects

Generated element	How the ID is used
Controller path variable	{id} is typed to the resolved ID’s Java type
Repository delete query	delete from {EntityName} e where e.{idProperty} = :id
Marker class constants	ID_CLASS, ID_PROPERTY

Using @SproutId to override

@SproutId lets you route Sprout’s operations through a different property than the JPA primary key:

@Entity
@SproutResource
public class User {
    @Id
    private Long dbId;     // JPA primary key — NOT used by Sprout for URLs

    @SproutId
    private String username; // Sprout routes GET/PUT/DELETE by this
}

Generated endpoints become /api/users/{username} (path variable type: String).

Caveat: default update ignores only "id"

The generated update service method uses:

BeanUtils.copyProperties(entity, existing, "id");

This explicitly skips copying a property literally named id. If your identifier property has a different name (e.g. username, bookId), the default update logic will overwrite it with whatever the client sends in the request body.

Recommendation: if you use @SproutId or @Id on a field not named id, override the update(...) method in your custom operations bean:

@Override
public Book update(String username, Book incoming) {
    Book existing = repository.findById(username)
        .orElseThrow(() -> new NoSuchElementException("Not found: " + username));
    // Copy safely, excluding your ID property explicitly:
    BeanUtils.copyProperties(incoming, existing, "username");
    return repository.save(existing);
}

See Customization for the full override pattern.