Hibernate bidirectional multi-pair multi-object Relational model mapping

1 bidirectional many-to-many

Business model:

Describe employees and projects

One employee can participate in multiple projects at the same time

Multiple employees can be included in a project

Analysis: The data model of the database, through the intermediate relational table, set up two one-to-many composition Many-to-many

1 Create TableEMP2 (3Enoint Primary KeyAuto_increment,4Enamevarchar5 );6 Create TableProject7 (8Pidint Primary KeyAuto_increment,9PNamevarchar,Ten ); One Create TableRelationship A ( -Enoint, -Pidint, the);

1.1 Describing the Java data Model

1.2 mapping configuration for Pojo

1.3 Loading a configuration file produces a database model

The database is a two primary foreign key.

1.4 for CRUD operations1.4.1 Adding employee information

1 @Test2  Public voidtestsaveemp ()3 {4Session session =hibernatesessionfactory.getsession ();5     //Open Transaction6Transaction TR =session.begintransaction ();7     //Create an Employee object8EMP emp =NewEmp ();9Emp.setename ("Chairman Mao");Ten Session.save (EMP); One tr.commit (); A session.close (); -}

1.4.2 Adding project information

1 @Test2  Public voidTestsaveproject ()3 {4Session session =hibernatesessionfactory.getsession ();5     //Open Transaction6Transaction TR =session.begintransaction ();7     //Create an Employee object8Project p =NewProject ();9P.setpname ("Arrival");Ten Session.save (p); One tr.commit (); A session.close (); -}

1.4.3 Add a project and assign an employee

New Add project, assign project to existing employee

1 /**2 * Add Project data to assign an existing employee3  * ****/4 @Test5  Public voidsaveprojectemp ()6 {7     //Get Session8Session session=sf.opensession ();9     //Open TransactionTenTransaction tr=session.begintransaction (); One     //Create a Project object AProject p=NewProject (); -P.setpname ("CRM"); -     //querying an employee's object theList<emp> elist = Session.createcriteria (Emp.class). List (); -     //assign an employee to a new project: Insert data into an intermediate table -P.setemps (NewHashSet (Elist)); - Session.save (p); +     //Commit a transaction - tr.commit (); +     //Freeing Resources A session.close (); at}

1.4.4 The relationship between employees and projects

The relationship is removed through the employee.

1 /***2 * Release of employee and project relationships3 * Delete data from the intermediate table4  * ***/5 @Test6  Public voiddeleteprojectemp ()7 {8     //Get Session9Session session=sf.opensession ();Ten     //Open Transaction OneTransaction tr=session.begintransaction (); A     //Querying Employee Objects -EMP emp = (EMP) session.get (EMP).class, 1); -     //get employee participation in all projects theSet<project> pros=Emp.getpros (); - System.out.println (pros); -     //Querying Project Objects -Project p= (Project) Session.get (project).class, 3); + System.out.println (p); -     /**** +      * A * The address of the element in the set set and a single query get the address of the project object, all the project objects in the Set collection and at * Single Query Gets the item object, is the same object, so Pros.remove (p), delete the address and P-like object in the collection -      * -      * *****/ -     //p.equals (obj); -     //remove an item from pros -     /*** in * The relationship is now disconnected by the employee (default inverse=false) - * Many-to-many This situation: Save the inverse=true of one side to      * ***/ +Pros.remove (P);// -     //Commit a transaction the tr.commit (); *     //Freeing Resources $ session.close ();Panax Notoginseng}

Hibernate bidirectional multi-pair multi-object Relational model mapping