One-to-one association ing (primary key + bidirectional)

One-to-one association ing (bidirectional) To implement one-to-one bidirectional Association ing, let's take the person and ID card as an example to understand:

Hibernate one-to-one primary key Association ing (two-way Association person <----> idcard) needs to add the <one-to-one> tag to the idcard ing file to point to person, it instructs hibernate how to load person based on primary key by default.

Step 1: first, establish the object relation class of the person and ID card:

Public class idcard { Private int ID; Private string cardno; Private person; // you must also hold an idcord reference in person. Public int GETID (){ Return ID; } Public void setid (int id ){ This. ID = ID; } Public String getcardno (){ Return cardno; } Public void setcardno (string cardno ){ This. cardno = cardno; } Public Person getperson (){ Return person; } Public void setperson (person ){ This. Person = person; }}

This is the object link class of person:

Public class person { Private int ID; Private string name; Private idcard; // you must also hold an idcord reference in person. Public int GETID (){ Return ID; } Public void setid (int id ){ This. ID = ID; } Public String getname (){ Return name; } Public void setname (string name ){ This. Name = Name; } Public idcard getidcard (){ Return idcard; } Public void setidcard (idcard ){ This. idcard = idcard; } }

Step 2: Create an object ing file:The person ing file of the person object is:

<Hibernate-mapping> <Class name = "com. bjsxt. hibernate. Person" table = "t_person"> <ID name = "ID"> <Generator class = "foreign"> <Param name = "property"> idcard </param> </Generator> </ID> <Property name = "name"/> <One-to-one name = "idcard" constrained = "true"/> </Class> <Class name = "com. bjsxt. hibernate. idcard" table = "t_idcard">
<ID name = "ID">
<Generator class = "native"/>
</ID>
<Property name = "cardno"/>
<One-to-one name = "person"/> // Add <one-to-one name = "person"/> to the idcord ing File
</Class>
</Hibernate-mapping> Step 3: add the hibernate configuration file: <Session-factory>
<Property name = "hibernate. Connection. url"> JDBC: mysql: // localhost/hibernate_one2one_pk_2 </property>
<Property name = "hibernate. Connection. driver_class"> com. MySQL. JDBC. Driver </property>
<Property name = "hibernate. Connection. username"> root </property>
<Property name = "hibernate. Connection. Password"> bjsxt </property>
<Property name = "hibernate. dialect"> org. hibernate. dialect. mysqldialect </property>
<Property name = "hibernate. show_ SQL"> true </property>
<Mapping Resource = "com/bjsxt/hibernate/idcard. HBM. xml"/>
<Mapping Resource = "com/bjsxt/hibernate/person. HBM. xml"/>
</Session-factory>
</Hibernate-configuration> Step 4: Write Test Code :
Public class one2onetest extends testcase {
Public void testsave1 (){
Session session = NULL;
Try {
Session = hibernateutils. getsession ();
Session. begintransaction ();
Idcard = new idcard ();
Idcard. setcardno ("88888888888888 ");
Person = new person ();
Person. setname ("dish 10 ");
Person. setidcard (idcard );
// Transientobjectexception does not occur
// Because the cascade attribute is default in one-to-one primary key Association ing
Session. Save (person );
Session. gettransaction (). Commit ();
} Catch (exception e ){
E. printstacktrace ();
Session. gettransaction (). rollback ();
} Finally {
Hibernateutils. closesession (session );
}
}
Public void testload1 (){
Session session = NULL;
Try {
Session = hibernateutils. getsession ();
Session. begintransaction ();
Person = (person) Session. Load (person. Class, 1 );
System. Out. println ("person. Name =" + person. getname ());
System. Out. println ("idcard. cardno =" + person. getidcard (). getcardno ());
Session. gettransaction (). Commit ();
} Catch (exception e ){
E. printstacktrace ();
Session. gettransaction (). rollback ();
} Finally {
Hibernateutils. closesession (session );
}
}
Public void testload2 (){
Session session = NULL;
Try {
Session = hibernateutils. getsession ();
Session. begintransaction ();
// Add from the idcord end
Idcard = (idcard) Session. Load (idcard. Class, 1 );
System. Out. println ("idcard. cardno =" + idcard. getcardno ());
System. Out. println ("idcard. Person. Name =" + idcard. getperson (). getname ());
Session. gettransaction (). Commit ();
} Catch (exception e ){
E. printstacktrace ();
Session. gettransaction (). rollback ();
} Finally {
Hibernateutils. closesession (session );
}
}
}