Hibernate Tree-like mapping

Example:

A class Org represents an organization and is a typical tree-like structure of data whose properties include:

Id,name,children,parent

To map the org to a database, make a many-to-one mapping of the parent and a one-to-many mapping of the children.

We can explain the relationship by three sheets.

Code implementation:

1. Build Org entity class

@Entitypublic class Org {private int id;private String name;private set<org> childen = new hashset<org> ();p Riv Ate Org parent; @Id @generatedvaluepublic 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;} @OneToMany (mappedby= "parent", Cascade={cascadetype.all},fetch=fetchtype.eager) public set<org> Getchilden () { return childen;} public void Setchilden (set<org> childen) {This.childen = Childen;} @ManyToOnepublic Org getParent () {return parent;} public void SetParent (Org parent) {this.parent = parent;}}

2. Build JUnit Test class

@Testpublic void Testdelete () {New Schemaexport (new Configuration (). Configure ()). Create (True, true);

Run the program, automatically generate the table org in the database, there are 3 properties: id,name,parent_id (foreign key)

3. Storing data

@Testpublic void Testsave () {Session session = Sf.getcurrentsession (); session.begintransaction (); org o = new org (); O. SetName ("head Office"); org O1 = new org (); O1.setname ("Branch 1"); org O2 = new org (); O2.setname ("Branch 2"); org o11 = new org (); o11.setname ("Branch 1_ Department 1"); org o12 = new org (); O12.setname ("Branch 1_ Department 2"); org o21 = new org (); O21.setname ("Branch 2_ Department 1"); O.getchilden (). Add (O1); O.getchilden (). Add (O2); O1.getchilden (). Add (o11); O1.getchilden (). Add (o12); O2.getchilden (). Add (o21); o11. SetParent (O1); o12.setparent (O1); O21.setparent (O2); O1.setparent (o); O2.setparent (o); Session.save (o); Session.gettransaction (). commit ();}

4. Print output

@Testpublic void TestLoad () {Session session = Sf.getcurrentsession (); session.begintransaction (); org o = (org) Session.load (Org.class, 1);p rint (o,0); Session.gettransaction (). commit ();} The name of the private void print (Org o,int level) {for (int i=0;i<level;i++) {System.out.print ("----") of each object is printed and exported recursively, in a tree-like structure;} System.out.println (O.getname ()); for (Org Child:o.getchilden ()) {print (child,level+1);}}

Output results

Head Office ---- Branch 1-------- Branch 1_ Department 2-------- Branch 1_ Department 1---- Branch 2--------Branch 2_ Department 1