Use Hibernate3.6.10 for CRUD operations

Commit commit 1. Add a data record and add it to the transaction.

Package com. itheima. util; Import org. hibernate. Session; Import org. hibernate. SessionFactory; Import org. hibernate. cfg. Configuration; // Hibenate tool class Public class HibernateUtil { Private static SessionFactory sessionFactory; Static { Configuration cfg = new Configuration (). configure (); SessionFactory = cfg. buildSessionFactory (); } Public static Session getSession (){ Return sessionFactory. openSession (); } Public static void main (String [] args ){ Session s = getSession (); S. close (); } }

You can see the addition operation here, without writing hql statements, is to set the value through the object, which is the benefit of hibernate

@ Test

Publicvoid testaddPerson (){

Personp = new Person ();

P. setName ("Chen xingyu 1 ");

P. setBirthday (newDate ());

P. setGender ("male ");

Sessionsession = HibernateUtil. getSession ();

Transactiontx = session. beginTransaction (); Start transaction

Session. save (p); // prepare to execute the SQL statement

System. out. println (p. getName (); when executed, the console prints the insert statement, but the database does not have data

Tx. commit (); Submit the transaction

Session. close (); execute to this, only data in the database is available. Refresh the database and you can see

System. out. println (p );

}

2. query entities based on the Union primary key

Package com. itheima. domain;

Import java. io. Serializable;

// Hypothesis: Students without duplicate names

Public class Student implementsSerializable {

PrivateString firstName; // Primary key

PrivateString secondName; // Primary key

PrivateString gender;

PublicString getFirstName (){

ReturnfirstName;

}

Publicvoid setFirstName (String firstName ){

This. firstName = firstName;

}

PublicString getSecondName (){

ReturnsecondName;

}

Publicvoid setSecondName (String secondName ){

This. secondName = secondName;

}

PublicString getGender (){

Returngender;

}

Publicvoid setGender (String gender ){

This. gender = gender;

}

}

Configuration File student. hbm. xml

"-// Hibernate/Hibernate Mapping DTD 3.0 // EN" Http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd>

The following hql statement is not written and the get method is used for query.

// Query Objects Based on the Union primary key

@ Test

Publicvoid testQueryStudent (){

Sessionsession = HibernateUtil. getSession ();

// Set the federated primary key

Students1 = new Student ();

S1.setFirstName ("zhting ");

S1.setSecondName ("w ");

Students = (Student) session. get (Student. class, s1); // joint primary key: Use the entity class itself as a condition

System. out. println (s );

Session. close ();

}

3. Three states of persistent objects in Hibernate and their mutual conversion

4. hibernate Cache

// Session cache: Level 1 Cache Public class HibernateDemo3 { // Verify the existence of the cache @ Test Public void testaddStudent (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // same as OID Person p2 = (Person) session. get (Person. class, 1); // same as OID. Because this object exists in the cache, it is directly retrieved and will not be queried in the database again. System. out. println (p1 = p2); // true Tx. commit (); Session. close (); } // Manage the first-level cache /* * Session. flush (): refresh the cache (synchronize the database ). The cached data is still * Session. clear (): clears the cache. * Session. evict (): clears the specified object. */ @ Test Public void testSessionManager1 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. System. out. println (p1 ); // Session. flush (); // only updates the database. The data in the cache is still // Session. clear (); // clear the cache Session. evict (p1); // clear the specified object from the cache Person p2 = (Person) session. get (Person. class, 1 ); System. out. println (p2 ); Tx. commit (); Session. close (); } // Snapshot: // Refresh when commit is enabled @ Test Public void testSessionManager2 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. P1.setName ("Chen xingyu 2"); // refresh database data can only refresh persistent child entities Tx. commit (); // synchronize the database at this time Session. close (); } @ Test // Manual flush will refresh Public void testSessionManager3 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. P1.setName ("Chen xingyu"); // refresh database data can only refresh persistent child entities Session. flush (); // synchronize the database Tx. commit (); // synchronize the database at this time Session. close (); } @ Test // During Query execution, the changed object classes are automatically synchronized to the database. Public void testSessionManager4 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. P1.setName ("Chen xingyu 1"); // refresh database data can only refresh persistent State entities Query q = session. createQuery ("from Person"); // a mandatory SQL statement System. out. println (q. list (). get (0 )); Session. flush (); // synchronize the database Tx. commit (); // synchronize the database at this time Session. close (); } @ Test // Verify the refresh Mode Public void testSessionManager5 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); // Session. setFlushMode (FlushMode. COMMIT); // when the transaction is committed and manually flush. Not flushed during Query // Session. setFlushMode (FlushMode. MANUAL); // when the transaction is committed and manually flush. Not flushed during Query Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. P1.setName ("Chen xingyu"); // refresh database data can only refresh persistent child entities Query q = session. createQuery ("from Person"); // a mandatory SQL statement System. out. println (q. list (). get (0); // get from Cache Tx. commit (); // synchronize the database at this time Session. flush (); // synchronize the database Session. close (); } // Refresh: overwrites the cached data with the data in the database. @ Test Public void testSessionManager6 (){ Session session = HibernateUtil. getSession (); Transaction tx = session. beginTransaction (); Person p1 = (Person) session. get (Person. class, 1); // get the Persistent Object and put it in the Session cache. P1.setName ("Chen xingyu "); Session. refresh (p1); // overwrite the cached data with the data in the database Tx. commit (); // synchronize the database at this time Session. close (); } }

The above fl means to update data to the database. If it is not flushed out, it means not to update (synchronize) the data to the database.

5. Common Methods for Session interfaces in hibernate (CUD addition, deletion, and modification)

// Common Session Methods Public class HibernateDemo1 { // If the primary key of the object class is the proxy primary key. The manually set id is invalid. // Save: instantaneous ---> persistent @ Test Public void test1 (){ Person p = new Person (); P. setName ("Wang Dong "); P. setBirthday (new Date ()); P. setGender ("female "); Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); P. setId (100); // unused. S. save (p); // plan to execute an insert statement P. setId (10); // an error is returned. In this case, the p object is persistent and ID cannot be changed. Tx. commit (); // actually executed. FlushMode. AUTO. S. close (); } // Update: disconnected ---> persistent // Execute the update operation if the object is changed only. @ Test Public void test2 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); Person p = (Person) s. get (Person. class, 1); // persistent state S. evict (p); // exit the tube P. setName ("xingyu "); S. update (p); // if the object is an unmanaged object, the update statement will be executed no matter whether the object is changed or not. Tx. commit (); // actually executed. FlushMode. AUTO. S. close (); } // // SaveOrUpdate () // The object is in the Instantaneous State. If the OID is null, save. Determine the configuration file // The object is out of control: OID has, and update is executed. @ Test Public void test3 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); // Skip --> persistent: update // Person p = (Person) s. get (Person. class, 1); // persistent state // S. evict (p); // exit the tube // P. setName ("xingyu "); // S. saveOrUpdate (p); // if the object is an unmanaged object, the update statement is executed no matter whether the object is changed or not. // Instantaneous ---> persistent: save Person p = new Person (); P. setName ("Yang Xianbin "); P. setBirthday (new Date ()); P. setGender ("female "); S. saveOrUpdate (p); // execute save Tx. commit (); // actually executed. FlushMode. AUTO. S. close (); } // @ Test Public void test4 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); Person p = (Person) s. get (Person. class, 1 ); S. evict (p ); S. saveOrUpdate (p); // insert. If id is 1, the framework treats it as an instantaneous object. Tx. commit (); // actually executed. FlushMode. AUTO. S. close (); } // SaveOrUpdate (): If a persistent State object is operated, it will not change. @ Test Public void test5 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); Person p = (Person) s. get (Person. class, 1 ); S. saveOrUpdate (p ); Tx. commit (); S. close (); } // Difference between get and load: // 1. get instant retrieval; load indicates delayed retrieval (Agent Class) // 2. If get gets a record that does not exist in the id database, null is returned; load throws an exception. @ Test Public void test6 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); // Person p = (Person) s. get (Person. class, 100); // print null Person p = (Person) s. load (Person. class, 100); // throw an exception System. out. println (p ); Tx. commit (); S. close (); } // Delete: The duration changes to instantaneous. @ Test Public void test7 (){ Session s = HibernateUtil. getSession (); Transaction tx = s. beginTransaction (); Person p = (Person) s. load (Person. class, 1 ); S. delete (p); // The deletion statement is scheduled to be executed. Tx. commit (); // actually executed S. close (); } }