Jpa basics (14): inheritance ing in JPA

Employee. Java: (base class)

 1 @ Entity
 2 @ Inheritance (Strategy = inheritancetype. single_table) //  Select an inheritance Policy  
  3 @ Discriminatorcolumn (name = "type ") //  Configure the authenticator  
  4 @ Discriminatorvalue ("0 ") //  Set the authenticator Value  
  5  Public   Class Employee {
 6 @ ID
 7 @ Generatedvalue
 8       Private Integer ID;
 9       Private String name;
 10       Public Integer GETID (){
 11           Return ID;
12 }
 13       Public   Void Setid (integer ID ){
 14           This . ID = ID;
 15 }
 16       Public String getname (){
 17           Return Name;
 18 }
19       Public   Void Setname (string name ){
 20           This . Name = Name;
 21 }
 22 }

Where@ Inheritance (Strategy = inheritancetype. single_table) // select an inheritance PolicyYou can select multiple policies, as shown in:

• Joined: the inherited child classes generate a table.
• Single_table: generate only one table and use one field as the authenticator
• Table_per_class: each class produces a table, including the base class.

 

Skiller. Java (inherited from employee. Java)

1 @ Entity
 2 @ Discriminatorvalue ("1 ")
 3   Public   Class Skiller Extends Employee {
 4       Private String skill;
 5  
 6       Public String getskill (){
 7          Return Skill;
 8 }
 9  
 10       Public   Void Setskill (string skill ){
 11           This . Skill = skill;
 12 }
 13 }

Sales. Java (inherited from employee. Java)

 1 @ Entity
2 @ Discriminatorvalue ("2 ")
 3   Public   Class Sales Extends Employee {
 4       Private String delimiter;
 5       Public String getask (){
 6           Return Break;
 7 }
8       Public   Void Setparts (string parts ){
 9           This . Bytes = bytes;
 10 }
 11 }

Test:

 1 @ Test
 2       Public   Void Save (){
 3 Entitymanagerfactory factory = persistence. createentitymanagerfactory ("sample ");
 4 Entitymanager em = factory. createentitymanager ();
 5 Em. gettransaction (). Begin ();
 6 Employee p1 = New Employee ();
 7 P1.setname ("Jim ");
 8 Skiller P2 = New Skiller ();
 9 P2.setname ("hanson ");
10 P2.setskill ("skill ");
 11 Sales P3 = New Sales ();
 12 P3.setname ("Brian ");
 13 P3.setvalues ("sale ");
 14 Em. persist (P1 );
 15 Em. persist (P2 );
 16 Em. persist (P3 );
 17 Em. gettransaction (). Commit ();
18 Em. Close ();
 19 Factory. Close ();
 20 }

Open the database: