This is an example of how to set limit in Hibernate query result. In order to set limit to a query result in Hibernate we have set the example below:
Employeeclass is the class whose objects will be inserted to the database.- In
SetLimitInHibernateQueryResultwe use the Hibernate API to make the interface with the database. - We create a new
Configuration, that allows the application to specify properties and mapping documents to be used when creating aSessionFactory. Usually an application will create a singleConfiguration, build a single instance ofSessionFactoryand then instantiateSessionsin threads servicing client requests. Usingconfigure()API method we use the mappings and properties specified in an application resource namedhibernate.cfg.xml. Then, withbuildSessionFactory()we instantiate a newSessionFactory, using the properties and mappings in this configuration. - Use the
getCurrentSession()API method to obtain the current session. - Use the
beginTransaction()API method to begin a unit of work and return the associatedTransactionobject. If a new underlying transaction is required, begin the transaction. Otherwise continue the new work in the context of the existing underlying transaction. - Create a new
Employeeobject and usesave(Object object)API method ofSessionto persist the given transient instances to the database. - Use
getTransaction()API method ofSessionandcommit()API method of Transaction to commit theTransaction. - Use the
beginTransaction()API method again. Now create a newQuery, using thecreateQuery(String queryString)API method of Session, with a given query. - Use
setMaxResults(int maxResults)to set the maximum number of rows to retrieve. - Use the
list()API method of Query to get the results. - Use again
getTransaction()API method of Session andcommit()API method of Transaction to commit the Transaction.
In the code snippets that follow, you can see the Employee class and the SetLimitInHibernateQueryResultClass that applies all above steps. You can also take a look at the hibernate.cfg.xml file, that holds all configuration for Hibernate, such as JDBC connection settings, and employee.hbm.xml file that holds the mapping configuration between the Employee class and the Employee table.
package com.javacodegeeks.snippets.enterprise;
import java.util.Date;
import java.util.List;
import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class SetLimitInHibernateQueryResult {
@SuppressWarnings("unchecked")
public static void main(String[] args) {
SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.getCurrentSession();
try {
session.beginTransaction();
for (int i = 0; i < 20; i++) {
Employee employee = new Employee();
employee.setName("employe_"+i);
employee.setSurname("surname_"+i);
employee.setTitle("QA Engineer_"+i);
employee.setCreated(new Date());
session.save(employee);
}
session.getTransaction().commit();
}
catch (HibernateException e) {
e.printStackTrace();
session.getTransaction().rollback();
}
session = sessionFactory.getCurrentSession();
try {
session.beginTransaction();
Query query = session.createQuery("from Employee");
query.setMaxResults(10);
List<Employee> employees = (List<Employee>) query.list();
if (employees!=null) {
System.out.println("Total Results:" + employees.size());
for (Employee employee : employees) {
System.out.println(employee.getId() + " - " + employee.getName());
}
}
session.getTransaction().commit();
}
catch (HibernateException e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}
}
hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- JDBC connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/companydb</property>
<property name="connection.username">jcg</property>
<property name="connection.password">jcg</property>
<!-- JDBC connection pool, use Hibernate internal connection pool -->
<property name="connection.pool_size">5</property>
<!-- Defines the SQL dialect used in Hiberante's application -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Display and format all executed SQL to stdout -->
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">update</property>
<!-- Mapping to hibernate mapping files -->
<mapping resource="Employee.hbm.xml" />
</session-factory>
</hibernate-configuration>
Employee.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.javacodegeeks.snippets.enterprise.Employee" table="employee">
<id name="id" column="id">
<generator class="native"/>
</id>
<property name="name" not-null="true" length="50" />
<property name="surname" not-null="true" length="50" />
<property name="title" length="50" />
<property name="created" type="timestamp" />
</class>
</hibernate-mapping>
CREATE TABLE `companydb`.`employee` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT, `name` VARCHAR(45) NOT NULL, `surname` VARCHAR(45) NOT NULL, `title` VARCHAR(45) NOT NULL, `created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (`id`) );
Output:
Total Results:10
44 - employe_0
45 - employe_1
46 - employe_2
47 - employe_3
48 - employe_4
49 - employe_5
50 - employe_6
51 - employe_7
52 - employe_8
53 - employe_9
This was an example of how to set limit in Hibernate query result.
