Welcome to the Hibernate Criteria Example Tutorial. Today we will look into Criteria in Hibernate.
Hibernate Criteria
Most of the times, we use HQL for querying the database and getting the results. HQL is not preferred way for updating or deleting values because then we need to take care of any associations between tables.
Hibernate Criteria API provides object oriented approach for querying the database and getting results. We can’t use Criteria in Hibernate to run update or delete queries or any DDL statements. Hibernate Criteria query is only used to fetch the results from the database using object oriented approach.
For my Hibernate criteria example, I will use the same setup as in my HQL Example and show you how to use Criteria in Hibernate for querying databases.
Some of the common usage of Hibernate Criteria API are;
- Hibernate Criteria API provides Projection that we can use for aggregate functions such as sum(), min(), max() etc.
- Hibernate Criteria API can be used with
ProjectionListto fetch selected columns only. - Criteria in Hibernate can be used for join queries by joining multiple tables, useful methods for Hibernate criteria join are createAlias(), setFetchMode() and setProjection()
- Criteria in Hibernate API can be used for fetching results with conditions, useful methods are add() where we can add Restrictions.
- Hibernate Criteria API provides addOrder() method that we can use for ordering the results.
Below class shows different usages of Hibernate Criteria API, most of these are replacements of examples in HQL tutorial.
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package com.journaldev.hibernate.main; import java.util.Arrays; import java.util.List; import org.hibernate.Criteria; import org.hibernate.FetchMode; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.criterion.Order; import org.hibernate.criterion.ProjectionList; import org.hibernate.criterion.Projections; import org.hibernate.criterion.Restrictions; import com.journaldev.hibernate.model.Employee; import com.journaldev.hibernate.util.HibernateUtil; public class HibernateCriteriaExamples { @SuppressWarnings("unchecked") public static void main(String[] args) { // Prep work SessionFactory sessionFactory = HibernateUtil.getSessionFactory(); Session session = sessionFactory.getCurrentSession(); Transaction tx = session.beginTransaction(); //Get All Employees Criteria criteria = session.createCriteria(Employee.class); List<Employee> empList = criteria.list(); for(Employee emp : empList){ System.out.println("ID="+emp.getId()+", Zipcode="+emp.getAddress().getZipcode()); } // Get with ID, creating new Criteria to remove all the settings criteria = session.createCriteria(Employee.class) .add(Restrictions.eq("id", new Long(3))); Employee emp = (Employee) criteria.uniqueResult(); System.out.println("Name=" + emp.getName() + ", City=" + emp.getAddress().getCity()); //Pagination Example empList = session.createCriteria(Employee.class) .addOrder(Order.desc("id")) .setFirstResult(0) .setMaxResults(2) .list(); for(Employee emp4 : empList){ System.out.println("Paginated Employees::"+emp4.getId()+","+emp4.getAddress().getCity()); } //Like example empList = session.createCriteria(Employee.class) .add(Restrictions.like("name", "%i%")) .list(); for(Employee emp4 : empList){ System.out.println("Employees having 'i' in name::"+emp4.getName()+","+emp4.getAddress().getCity()); } //Projections example long count = (Long) session.createCriteria(Employee.class) .setProjection(Projections.rowCount()) .add(Restrictions.like("name", "%i%")) .uniqueResult(); System.out.println("Number of employees with 'i' in name="+count); //using Projections for sum, min, max aggregation functions double sumSalary = (Double) session.createCriteria(Employee.class) .setProjection(Projections.sum("salary")) .uniqueResult(); System.out.println("Sum of Salaries="+sumSalary); //Join example for selecting few columns criteria = session.createCriteria(Employee.class, "employee"); criteria.setFetchMode("employee.address", FetchMode.JOIN); criteria.createAlias("employee.address", "address"); // inner join by default ProjectionList columns = Projections.projectionList() .add(Projections.property("name")) .add(Projections.property("address.city")); criteria.setProjection(columns); List<Object[]> list = criteria.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } // Rollback transaction to avoid messing test data tx.commit(); // closing hibernate resources sessionFactory.close(); } } |
When we execute above Hibernate Criteria example program, we get following output.
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May 26, 2014 6:53:32 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit> INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final} May 26, 2014 6:53:32 PM org.hibernate.Version logVersion INFO: HHH000412: Hibernate Core {4.3.5.Final} May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment <clinit> INFO: HHH000206: hibernate.properties not found May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment buildBytecodeProvider INFO: HHH000021: Bytecode provider name : javassist May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration configure INFO: HHH000043: Configuring from resource: hibernate.cfg.xml May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration getConfigurationInputStream INFO: HHH000040: Configuration resource: hibernate.cfg.xml May 26, 2014 6:53:32 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity WARN: HHH000223: Recognized obsolete hibernate namespace https://hibernate.sourceforge.net/. Use namespace https://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide! May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration doConfigure INFO: HHH000041: Configured SessionFactory: null Hibernate Configuration loaded Hibernate serviceRegistry created May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure WARN: HHH000402: Using Hibernate built-in connection pool (not for production use!) May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator INFO: HHH000401: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost/TestDB] May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator INFO: HHH000046: Connection properties: {user=pankaj, password=****} May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator INFO: HHH000006: Autocommit mode: false May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure INFO: HHH000115: Hibernate connection pool size: 20 (min=1) May 26, 2014 6:53:32 PM org.hibernate.dialect.Dialect <init> INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4 May 26, 2014 6:53:32 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService INFO: HHH000399: Using default transaction strategy (direct JDBC transactions) May 26, 2014 6:53:32 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init> INFO: HHH000397: Using ASTQueryTranslatorFactory Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id ID=1, Zipcode=95129 ID=2, Zipcode=95051 ID=3, Zipcode=560100 ID=4, Zipcode=100100 Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id where this_.emp_id=? Name=Lisa, City=Bangalore Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id order by this_.emp_id desc limit ? Paginated Employees::4,New Delhi Paginated Employees::3,Bangalore Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id where this_.emp_name like ? Employees having 'i' in name::David,Santa Clara Employees having 'i' in name::Lisa,Bangalore Hibernate: select count(*) as y0_ from EMPLOYEE this_ where this_.emp_name like ? Number of employees with 'i' in name=2 Hibernate: select sum(this_.emp_salary) as y0_ from EMPLOYEE this_ Sum of Salaries=1000.0 Hibernate: select this_.emp_name as y0_, address1_.city as y1_ from EMPLOYEE this_ inner join ADDRESS address1_ on this_.emp_id=address1_.emp_id [Pankaj, San Jose] [David, Santa Clara] [Lisa, Bangalore] [Jack, New Delhi] May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost/TestDB] |
Since I am using HQL example project, you would need to import that and then add this class for it to be working.
Notice the hibernate queries executed in the output, this way you can refine your queries and get the results you are looking for. That’s all for a quick roundup on Criteria in Hibernate.