Hibernate05--list and iterator

/** *  * @authorSmall Tofu * After you, will thank you for your efforts now! Efforts! Insist! Don't give up! */ Public classstudenttest {Configuration Configuration=NULL; Sessionfactory sessionfactory=NULL; Session Session=NULL; Transaction Transaction=NULL; //test methods have the same code block@Before Public voidbefore () {//01. Load configuration file (Hibernate.cfg.xml) must be located in src root directoryConfiguration =NewConfiguration (). Configure (); //02. Create a session factory set into singleton modeSessionfactory =configuration.buildsessionfactory (); //03. Session HttpSession (user session) created through the factorySession =sessionfactory.opensession (); //04. Using object-oriented thinking to manipulate database additions and deletions must open transactionsTransaction =session.begintransaction (); } @After//Close Session     Public  voidAfter () {//no session in query does non-null validation        if(session!=NULL) {            //05. Close SessionSession.close (); }    }    /*** Hql:hibernate's query Language! * * The steps to execute the HQL statement: * 01. Get session * 02. Write HQL statement * 03.session.     Creatquery (HQL); Create a Query Object * 04. Execute Queries * * * LIST (): Whether we clear the cache or not, simply query the database to generate a SELECT statement if it is a list ()! */@Test Public  voidtestlist () {//String sql= "select * from Stu"; Stu is the table nameString hql= "from Student";//Student must be a class name//get the Query objectQuery query =session.createquery (HQL); //Start QuerySystem.out.println ("**************"); List List= Query.list ();//there is only one SQL statementSystem.out.println ("**************");  for(Object object:list) {System.out.println (object); } session.clear (); //Empty Cache//whether we clear the cache or not, as long as the list () queries the database to produce a SELECT statement immediatelyList list2=query.list (); }        /*** Iterator (): * 01. Execute N+1 Query statement without caching * First query ID statement in query.iterate (); Time to produce!     * The remaining n statements are generated at Iterate.hasnext ()! * N represents the total number of records in the database*/@Test Public  voidTestiterator () {String hql= "from Student";//Student must be a class nameQuery query =session.createquery (HQL); System.out.println ("**************"); Iterator Iterate=query.iterate (); System.out.println ("**************");  while(Iterate.hasnext ()) {Object Object=(Object) iterate.next ();        System.out.println (object); }    }        /*** 02. There is a cache situation * Query all student information!     * Iterate (): Execute an SQL statement! */@Test Public  voidTestIterator2 () {String hql= "From Stu"; Query Query=session.createquery (HQL); List List= Query.list ();//now that the SQL statement has been generated, all student are already in the session cache.System.out.println ("*********************"); Iterator Iterate=query.iterate (); System.out.println ("*********************");  while(Iterate.hasnext ()) {Object Object=(Object) iterate.next ();        System.out.println (object); }    }        /*** Get: Generate 1 Strips * iterate (): Generate 1 * iterate.hasnext (): 3 Results*/@Test Public  voidTestIterator3 () {Student stu= (Student) session.get (Student.class, 1);//now the cache has an object with ID 1String hql= "from Student"; Query Query=session.createquery (HQL); Iterator Iterate=query.iterate (); System.out.println ("*********************");  while(Iterate.hasnext ()) {Object Object=(Object) iterate.next ();        System.out.println (object); }    }}

Hibernate05--list and iterator