Hibernate basic examples

Example shows basic hibernate usage:

person.hbm.xml

<hibernate-mapping>
<class name="com.test.model.Person" table="person" >

<id name="personId" type="int">
<column name="person_id" />
<generator class="sequence">
<param name="sequence">NEXT_PERSON_ID</param>
<param name="parameters">INCREMENT BY 1 START WITH 1</param>
</generator>
</id>
<property name="personAge" type="java.lang.Integer">
<column name="person_age" />
</property>
<property name="personName" type="string">
<column name="person_name" length="3" not-null="true" />
</property>
<property name="personDateOfBirth" type="date">
<column name="person_dob" length="4" />
</property>
<property name="updateTime" type="timestamp">
<column name="update_time" length="3594" />
</property>

We ca also properties to fetch another table data lazily as:
<property name="personRoles" lazy="false" type="string" >
<formula>
(select pr.person_role from PersonRole pr where pr.person_id=person_id)
</formula>
</property>

One to Many mapping returning a List
<list name="personRoles" lazy="true" fetch="select" inverse="true">
<key>
<column name="person_id" />
<column name="person_role" />
</key>
<list-index column="role_seq" base="1"/>
<one-to-many class="com.test.model.PersonRole" />
</list>

One to Many mapping returning a Set
<set name="personRoles" order-by="role_seq" lazy="true" fetch="select" inverse="true">
<key>
<column name="person_id" />
<column name="person_role" />
</key>


Model class to represent this would be as follows:

public class Person implements java.io.Serializable
{

private int personId;
private Integer personAge;
private String personName;
private Date personDateOfBirth;
private Date updateTime;

// setters and getters
}


DAO to access the persistence layer

class PersonDAOHibernateImpl extends PersonDAO
{
public List<Person> getPersonList()
{
try
{
beginTransaction();
Session session = getSession();
List<Person> instList = session.createCriteria(Person.class)
.addOrder(Order.desc("personId"))
.list();

commitTransaction();
return instList;
}
catch(Exception e)
{
rollbackTransaction();
return Collections.emptyList();
}

}


Some other kind of queries we can use are:

To get a specific name list
List<Person> instList = session.createCriteria(Person.class)
.add(Restrictions.eq("personName", Integer.valueOf(personName)))
.addOrder(Order.desc("personId"))
.list();

can also use this clause in above query where we have a composite id
.add(Restrictions.eq("id.name", Integer.valueOf(personName)))

or
Query q = getSession().createQuery("select personName from Person");
List<Person> personList = q.list();

or if we need to make a join on another table say for example called PersonRoles
Criteria c = session.createCriteria(Person.class)
.add(Restrictions.eq("id.name", Integer.valueOf(personId)))
.setFetchMode("roles", FetchMode.JOIN)
.createAlias("roles", "personRoles", CriteriaSpecification.LEFT_JOIN)
.addOrder(Order.asc("id.personId"))
.addOrder(Order.asc("personRoles.id.roleName"))
.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);

or we can create a plain sql statement and query
String updatePerson =
" update person " +
" SET person_name = 'ABC' " +
" WHERE person_id = ? ";

Session session = getSession();
beginTransaction();
Connection conn = session.connection();

PreparedStatement pstmt = conn.prepareStatement(updatePerson);
pstmt.setInt(1, personId);
pstmt.execute();
pstmt.close();

Couple of helpful Ant tasks

<target name="hibernatetool" description="Run Hibernate Tool" unless="hibernate.skip" depends="">
<mkdir dir="${src.resources.hibernate.generated}" />
<echo message="ANT HEAP SIZE = ${env.ANT_OPTS}" />
<taskdef name="hibernatetool" classname="org.hibernate.tool.ant.HibernateToolTask" classpathref="hibernatetools.path" />

<hibernatetool destdir="${src.resources.hibernate.generated}" templatepath="${src.resources.hibernate}">
<jdbcconfiguration
revengfile="${src.resources.hibernate}/hibernate.reveng.xml"
configurationfile="${src.resources.hibernate}/hibernate.cfg.xml"
packagename="${package.name}" />

<hbm2hbmxml/> <!-- This regenerates the hbm mapping files -->

<!-- <hbm2cfgxml/> This cretaes a hibernate.cfg.xml file -->
</hibernatetool>
</target>


<target name="hbm2java" description="Run Hibernate Tool" unless="hibernate.skip" depends="">
<taskdef name="hibernatetool" classname="org.hibernate.tool.ant.HibernateToolTask"
classpathref="hibernatetools.path"
/>

<hibernatetool destdir="${src.resources.hibernate.generated}">
<configuration>
<fileset dir="${src.resources.hibernate.generated}">
<include name="**/Person*.hbm.xml" />
</fileset>
</configuration>

<hbm2java jdk5="false" ejb3="false" />
</hibernatetool>
</target>


hibernate.cfg.xml

<hibernate-configuration>

<session-factory>
<!-- Bind the getCurrentSession() method to the thread, session-per-conversation -->
<property name="current_session_context_class">org.hibernate.context.ThreadLocalSessionContext</property>

<property name="hibernate.connection.url">jdbc:informix-sqli:myhostname:myportnumber/mydatabasename:INFORMIXSERVER=myservername</property>
<property name="hibernate.connection.username">myusername</property>
<property name="hibernate.connection.password">mypassword</property>

<property name="hibernate.connection.release_mode">auto</property>

<property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
<property name="hibernate.connection.driver_class">com.informix.jdbc.IfxDriver</property>
<property name="dialect">org.hibernate.dialect.InformixDialect</property>
<property name="show_sql">true</property>

<!-- Connection Pool -->
<property name="hibernate.connection.pool_size">3</property>
<property name="hibernate.c3p0.min_size">1</property>
<property name="hibernate.c3p0.max_size">5</property>
<property name="hibernate.c3p0.timeout">1800</property>
<property name="hibernate.c3p0.max_statements">100</property>

<!-- Use EHCache as secondary cache-->
<property name="hibernate.cache.use_query_cache">true</property>
<property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>


<mapping resource="com/mytest/persistence/orm/hibernate/model/Person.hbm.xml" />

</session-factory>
</hibernate-configuration>


hibernate.reveng.xml

<hibernate-reverse-engineering>
<type-mapping>
<sql-type jdbc-type="5" hibernate-type="integer"/>
</type-mapping>
<table-filter match-catalog="mydatabasename" match-schema="informix" match-name="person" exclude="false" />
</hibernate-reverse-engineering>