hibernate
Set limit in Hibernate query result
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:
Employee
class is the class whose objects will be inserted to the database.- In
SetLimitInHibernateQueryResult
we 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 ofSessionFactory
and then instantiateSessions
in 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 associatedTransaction
object. 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
Employee
object and usesave(Object object)
API method ofSession
to persist the given transient instances to the database. - Use
getTransaction()
API method ofSession
andcommit()
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.
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | 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
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | <? xml version = '1.0' encoding = 'utf-8' ?> <! DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" < 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
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | <? xml version = "1.0" ?> <! DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" < 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 > |
1 2 3 4 5 6 7 8 | 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.