Hibernate 4. Delay loading

Delay Loading:

The query statement is sent to the database only if the attribute (except the primary key attribute) is used with the entity object

Get does not support deferred loading

@Testpublic void Gettest () {Session session=null; Student student=null;try{session=hibernateutil.opensession (); student= (Student) Session.get (Student.class, 3); SYSTEM.OUT.PRINTLN ("ID:" +student.getstudentid ()); System.out.println ("Name:" +student.getstudentname ());} Finally{session.close ();}}

Results:

Hibernate:select student0_.student_id as student1_0_0_, student0_.student_name as student2_0_0_, student0_.age as age0_ 0_ from T_student student0_ where student0_.student_id=?id:3name:ddddd

A query statement has been issued when the Get method is called

Load supports deferred loading

@Testpublic void LoadTest () {Session session=null; Student student=null;try{session=hibernateutil.opensession (); student= (Student) session.load (Student.class, 3); SYSTEM.OUT.PRINTLN ("ID:" +student.getstudentid ()); System.out.println ("Name:" +student.getstudentname ());} Finally{session.close ();}}

Results:

Id:3hibernate:select student0_.student_id as student1_0_0_, student0_.student_name as student2_0_0_, student0_.age as age0_0_ from T_student student0_ where student0_.student_id=?name:ddddd

When the load method is called, a proxy object is returned, and no query statement is issued, and the query statement is issued when the Studentname property is required

After closing the session

Get

@Testpublic void Get2test () {Session session=null; Student student=null;try{session=hibernateutil.opensession (); student= (Student) Session.get (Student.class, 3);} Finally{session.close ();} SYSTEM.OUT.PRINTLN ("ID:" +student.getstudentid ()); System.out.println ("Name:" +student.getstudentname ());}

Results:

Hibernate:select student0_.student_id as student1_0_0_, student0_.student_name as student2_0_0_, student0_.age as age0_ 0_ from T_student student0_ where student0_.student_id=?
Id:3name:ddddd

Same as the result in the session scope

Load

@Testpublic void Load2test () {Session session=null; Student student=null;try{session=hibernateutil.opensession (); student= (Student) session.load (Student.class, 3);} Finally{session.close ();} SYSTEM.OUT.PRINTLN ("ID:" +student.getstudentid ()); System.out.println ("Name:" +student.getstudentname ());}

Results:

Id:3org.hibernate.lazyinitializationexception:could not initialize Proxy-no Session

Cast exception, visible delay loading is only valid within the scope of the session

Summary:

1. Only the query statement is sent to the database when the attribute (except the primary key attribute) is used with the entity object

2. Delay loading is only valid within the session's scope

Hibernate 4. Delay loading