Hibernate---Progress 1

Association mappings: http://www.cnblogs.com/huxi/archive/2009/12/15/1624988.html

First, hibernate's loading process

Two ways to load a 1.Hibernate configuration file

①configuration configuration = new configuration ();

Configuration.configure ();

Public Configuration Configure () throws hibernateexception{

Configure ("/hibernate.cfg.xml");

return this;

}

②configuration configuration = new configuration ();

Configuration.configure ("");

Public Configuration Configure (String Resource) throws hibernateexception{

Log.info ("Configuring from Resource:" +resource);

InputStream stream = Getconfigurationinputstream (Resource);

Return Doconfig (Stream,resource);

}

Second, CRUD operations

1. Create a configuration file that loads hibernate from a configuration object (a mapping resource file that contains realm classes and tables in the config file)

2. Get the Sessionfactory object from the Configuration object

3. Open Session:sessionFactory.openSession ();

4. Use the session to query

5. Turn on transaction: Session.beagintransaction (); Curd operation. Commit the transaction and close the session;

1  Public voidtestsave{2Configuration Configuration =NewConfiguration ();3     //load the Hibernate.cfg.xml under the Classpath4 configuration.configure ();5     //Call Sessionfactory6Sessionfactory SF =configuratiion.buildsessionfactory ();7     //Open Sessioin8Session s =sf.opensession ();9     //Open TransactionTenTransaction TR =s.begintransaction (); One     //to save the operation AObject obj =NewObject (); - Obj.set (); -     ......... the s.save (obj); - tr.commit (); -S.close ()

View Code

　　

Third, the relationship operation

1. The State of the object

Temporary Status: New

Persistent state: Get Save Update

Off-tube Status: Clear Close evict

　　

2, relational operations

2.1-to-one-and-one-to-many unidirectional association mappings

Many-to-one

12<className= "Bean. User "table=" T_user ">3<id name= "id" ><generatorclass= "Native"/></id>4<property name= "Name"/>5<!--to map a many-to-one relationship using "Many-to-one". A foreign key is automatically generated when you export the DDL--6<many-to-one name= "group" column= "GID"/>7         8</class>9Ten One<className= "Bean. Group "table=" T_group "> A<id name= "id" ><generatorclass= "Native"/></id> -<property name= "Name"/> -</class> the
One-to-many
12<className= "Bean. User "table=" T_user ">3<id name= "id" ><generatorclass= "Native"/></id>4<property name= "Name"/>5</class>678<className= "Bean. Group "table=" T_group ">9<id name= "id" ><generatorclass= "Native"/></id>Ten<property name= "Name"/> One<!--use Set mapping collection-- A<set name= "Users" > -<!--use "key" to specify foreign keys in the Foreign key table (T_user) that refer to itself-- -<key column= "gid"/> the<!--use one-to-many movies-- -<one-to-manyclass= "Bean. User "/> -</set> -</class> +
2.2 Bidirectional correlation
<!--bean/user.hbm.xml--className= "Bean. User "table=" T_user "> <id name=" id "><generatorclass= "Native"/></id> <property name= "name"/> <!--use <many-to-one> to map a many-to-one relationship. A foreign key is automatically generated when you export the DDL--<many-to-one name= "group" column= "gid"/> </class>className= "Bean. Group "table=" T_group "> <id name=" id "><generatorclass= "Native"/></id> <property name= "name"/> <!--use <set> Map Collection--<set name            = "Users" > <!--use <key> to specify foreign keys in the Foreign key table (T_user) referenced to itself--<key column= "gid"/> <!--using <one-to-many> mapping one-to-many relationships-<one-to-manyclass= "Bean. User "/> </set> </class>
In a bidirectional association, adding "Inverse=true" to "set" can flip the maintenance relationship: Hibernate will discard the maintenance from one end. User and group relationships must use user maintenance, and hibernate will not maintain this relationship when the group is operating.
<set name= "Users" inverse=true>
Operations Group Example
sessiion.begintransation (); User User=NewUser (); User.setname ("Bla"); Grop Group=NewGroup (); Group.setname ("Admin"); Group.setusers (NewHashSet ()); Group.getusers (). Add (user), Session.save (user); Session.save (group); Session.gettransaction (). Commit ();//maintenance at one end after flipping oversession.begintransaction (); Group Group=NewGroup (); Group.setname ("Admin"); User User=NewUser (); User.setname ("Zhang San"); User.setgroup (group); Session.save (group); Session.save (user); Session.gettransaction (). Commit ()
2.3 One-to-one correlation mappings
According to the mapping method, it can be divided into Primary Key association map and unique Foreign Key association mapping . The primary key association is to maintain the primary key consistency of the two tables and, if necessary, to add a foreign key constraint on the primary key; The unique foreign Key association is similar to a many-to-one association, which joins a foreign key column for a table, but a one-to-a association adds a unique constraint to the foreign key at the same time.
1. Primary Key correlation mapping
Primary key one-way Association
 <!--bean/user.hbm.xml--class  name= "Bean. User "table=" T_user "> <id name=" id "> <!--Specify the primary key generation policy as foreign key---<generator class  = "foreign" > <!--Specify properties to reference-<param name= "PR        Operty ">group</param> </generator> </id> <property name=" name "/> <!--use <one-to-one> map one-to-one relationships. --<one-to-one name= "group" > </class  >
<!--bean/group.hbm.xml    --class name= "beans. Group "table=" T_group ">        class=" Native "/></id>        <property name=" name "/>    </class>
Primary KEY Bidirectional Association
 <!--bean/user.hbm.xml--class  name= "Bean. User "table=" T_user "> <id name=" id "> <!--Specify the primary key generation policy as foreign key---<generator class  = "foreign" > <!--Specify properties to reference-<param name= "PR        Operty ">group</param> </generator> </id> <property name=" name "/> <!--use <one-to-one> map one-to-one relationships. --<one-to-one name= "group" > </class  >
<!--bean/group.hbm.xml    --class name= "beans. Group "table=" T_group ">        class=" Native "/></id>        <property name=" name "/>        <!--use <one-to-one> map one-to-one relationships-        <one-to-one name= "user"/>    </class></ Hibernate-mapping>
2. Unique FOREIGN key correlation mapping
Unidirectional
<!--bean/user.hbm.xml    --class name= "beans. User "table=" T_user ">        <id name=" id ">            class=" native "/>        </id>        < Property name= "Name"/>        <!--<many-to-one> Plus unique becomes one-to-one-        <many-to-one name= "group" Unique= "true" column= "gid"/>    </class>
<!--bean/group.hbm.xml    --class name= "beans. Group "table=" T_group ">        class=" Native "/></id>        <property name=" name "/>    </class>
Bidirectional
　　
 <!--bean/user.hbm.xml--class  name= "Bean. User "table=" T_user "> <id name=" id "> <generator class  =" n Ative "/> </id> <property name=" name "/> <!--<many-to-one> Plus unique becomes a one-to-one--&        Gt <many-to-one name= "group" unique= "true" column= "gid"/> </class  > 
<!--bean/group.hbm.xml    --class name= "beans. Group "table=" T_group ">        class=" Native "/></id>        <property name=" name "/>        <!--using <one-to-one> mapping one-to-        <one-to-one name= "user"/>    </class></ Hibernate-mapping>
2.4 Many-to-many associations
One-Way Association
　　
className= "Bean. User "table=" T_user "> <id name=" id "> <generatorclass= "Native"/> </id> <property name= "name"/> <!--using the Set mapping collection, Hibernate will generate a third table in a many-to-many relationship             --<set name= "groups" table= "T_user_group" > <!--use key to specify foreign keys in the Foreign key table (T_user_group) referenced to itself-- <key column= "userid" ></key> <!--use Many-to-one to map a many-to-many relationship, column specifies the other end of the columns in the table T_user_group- <many-to-manyclass= "Bean. Group "colun=" GroupID "></many-to-many> </set> </class>className= "Bean. Group "table=" T_group "> <id name=" id "><generatorclass= "Native"/></id> <property name= "name"/> </class>
Bidirectional correlation
<!--bean/user.hbm.xml    --class name= "beans. User "table=" T_user ">        <id name=" id ">            class=" native "/>        </id>        < Property name= "Name"/>        <!--use <set> Map collection, in a many-to-many relationship, Hibernate will generate a third table--        <set name= "groups" table= "T_user_group" >            <!--use <key> specify foreign keys in the Foreign key table (T_user_group) referenced to itself--            <key column= " UserID "/>            <!--use <many-to-many> map Many-to-many relationships, column specifies the other end in table T_user_group--            class = "Bean. Group "column=" GroupID "/>        </set>    </class>
<!--bean/group.hbm.xml    --class name= "beans. Group "table=" T_group ">        <id name=" id ">            class=" native "/>        </id>        < Property name= "Name"/>        <!--use <set> Map collection, Hibernate will generate a third table--        <set name= "Users" in many-to-many relationships table= "T_user_group" >            <!--use <key> to specify foreign keys in the Foreign key table (T_user_group) referenced to itself--            <key column= "group "/>            <!--use <many-to-many> map Many-to-many relationships, column specifies the other end in table T_user_group--            class=" Bean. User "column=" userid "/>        </set>    </class>
A many-to-many bidirectional association can also set inverse= "true" in <set> on one end of the relationship that you do not want to maintain, but there must be a side that can be maintained, that is, you can only set a single.
Iv. Benefits of Hibernate
V. HQL statements
 Hibernate---Progress 1