Topic: Hibernate Spanning Tree (annotation-based approach)

Java Code

Package Yingjun.model;
Import Java.util.HashSet;

Import Java.util.Set;
Import Javax.persistence.CascadeType;
Import javax.persistence.Entity;
Import Javax.persistence.FetchType;
Import Javax.persistence.GeneratedValue;
Import Javax.persistence.Id;
Import Javax.persistence.JoinColumn;
Import Javax.persistence.ManyToOne;


Import Javax.persistence.OneToMany;
	@Entity public class Tree {private int id;
	private String name;
	Private Tree parent;
	Private set<tree> children=new hashset<tree> ();
	@Id @GeneratedValue public int getId () {return Id;
	} public void setId (int id) {this.id = ID;
	} public String GetName () {return name;
	} public void SetName (String name) {this.name = name;
	} @ManyToOne @JoinColumn (name= "parent_id") public Tree getParent () {return parent;
	} public void SetParent (Tree parent) {this.parent = parent; } @OneToMany (mappedby= "parent", Cascade=cascadetype.all,fetch=fetchtype.eager) public set<tree> GetChildren () {REturn children;
	} public void Setchildren (set<tree> children) {This.children = children;
 }

	
}

Generated statement of the build table:

CREATE TABLE Tree (
        ID integer NOT NULL auto_increment,
        name varchar (255),
        parent_id Integer,
        Primary Key (ID)
    )

    ALTER TABLE Tree 
        add index fk27e7be9fd80f87 (parent_id), 
        add constraint fk27e7be9fd80f87 
        foreign Key (parent_id) 
        references Tree (ID)

Inserting data into the tree

@Test public
	void Testsavetree () {
		
		Session session=hibernateutil.getsessionfactory (). Getcurrentsession ();
		Session.begintransaction ();
		Tree tree1=new tree ();
		Tree1.setname ("picture");
		
		Tree tree2=new tree ();
		Tree2.setname ("photo");
		
		Tree tree3=new tree ();
		Tree3.setname ("poster");
		
		Tree tree4=new tree ();
		Tree4.setname ("My photo 1");
		
		Tree tree5=new tree ();
		Tree5.setname ("My photo 2");
		
		Tree1.getchildren (). Add (tree2);
		Tree1.getchildren (). Add (tree3);
		Tree2.getchildren (). Add (tree4);
		Tree2.getchildren (). Add (tree5);
		Tree2.setparent (tree1);
		Tree3.setparent (tree1);
		Tree4.setparent (tree2);
		Tree5.setparent (tree2);	
		
		Session.save (tree1);
		Session.gettransaction (). commit ();
	}

Results:

To fetch the data code from the tree:

@Test public
	void Testloadtree () {
		Session session=hibernateutil.getsessionfactory (). Getcurrentsession ();
		Session.begintransaction ();
		Tree t= (tree) session.load (Tree.class, 1);
		Print (t);
		Session.gettransaction (). commit ();
		
		
	}

	private void print (tree tree) {
		System.out.println (Tree.getname ());
		For (Tree Child:tree.getChildren ()) {
			print (child);
		}

To remove the result:

Reprint Source:

http://www.iteye.com/topic/1129579