Annotation Type Tree

@Documented
@Target(TYPE)
@Retention(RUNTIME)
public @interface Tree

Declarative annotation to indicate that the object of a class represents a node in a tree structure.

When this annotation is applied to a class, it informs the core API that the objects of this class can be organized into a tree structure, provided that they also have the @Id and @Parent annotations.

The HappyTree API is able to transform a data structure that represents, logically, a tree, but is physically organized in a linear form. Each object that has this annotation will represent a node in a tree. It happens when the API client passes a collection of linear objects that have a hierarchical relationship through the Id and Parent, to be organized into an actual tree structure through the TreeTransaction.initializeSession(String, java.util.Collection) method.

For instance, if there is, for any reason, a need to transform a data structure like this:

@Tree
public class Directory {
    @Id
    private long identifier;

    @Parent
    private long parentIdentifier;

    private String name; //(System32 for example)
    ...
}

into this:

        public class Element<Directory> {
                private Collection<Element<Directory>> children;
                private Directory wrappedNode; //The respective Directory
                
                ...
}

Then, the HappyTree API will process and transform it into an actual tree structure. This process is known as the API Transformation Process.

Note that in this example, there is a slight change in how the objects are related. In the first one, the parentIdentifier of an object references the identifier of another object, which conceptually represents the parent of the first one.

The second example shows that the relationship between the objects is slightly different, because, indeed, an object is literally inside of another one, and so on, representing an actual tree structure.

After the tree is built, it is possible to handle each element in a very flexible way (cut, copy, remove, etc.) through the TreeManager interface.

The getters and setters for the @Id and @Parent annotated fields are mandatory.

Author:

Diego Madson de Andrade Nóbrega