instanceof java
instanceof java is a java related one.
Hibernate Criteria Query Language (HCQL)
Posted: Nov 6, 2016 1:28 AM
This post originated from an RSS feed registered with Java Buzz
by instanceof java.
Original Post: Hibernate Criteria Query Language (HCQL)
Latest Java Buzz Posts
instanceof java
Instance Of Java
Advertisement
In Hibernate we pull the data from data base in two ways. session.get()/ session.load() Hibernate query langugae Now we will discuss about the third way Hibernate criteria query language which solves the problems of above two approaches.
Hibernate Criteria Query Language / HCQL
In order to fetch the records based on some criteria we use Hibernate Criteria Query Language. We can make select operation on tables by applying some conditions by using HCQL . Criteria API is the alternative to HQL in object oriented approach. Advantages of Hibernate Criteria Query Language (HCQL) Criteria API allows us to define criteria query object by applying rules ,filtration and logical conditions So that we can add criteria to query. Criteria Interface: Criteria Interface has some methods to specify criteria. Hibernate session interface has a method named createCriteria() to create criteria. public interface Criteria extends CriteriaSpecification Criteria criteria = session.createCriteria(Student.class); List<Student> studentList= criteria .list(); Methods of Criteria interface: Order Class public class Order extends Object implements Serializable By using Order class we can sort the records in ascending or descending order. Order class provides two different methods to make ascending and descending. public static Order asc(String propertyName) public static Order desc(String propertyName) Hibernate Criteria query example using order class Criteria criteria = session.createCriteria(Product.class) // To sort records in descening order criteria.addOrder(Order.desc("price")); // To sort records in ascending order criteria.addOrder(Order.asc("price")); Restrictions Class public class Restrictions extends Object Restrictions class provides methods that can be used add restrictions (conditions) to criteria object. We have many methods in Restrictions class some of the commonly using methods are. Hibernate Criteria query example using Restrictions class Criteria criteria = session.criteriaeateCriteria(Product.class); // To get records having price more than 3000 criteria.add(Restrictions.gt("price", 3000)); // To get records having price less than 2000 criteria.add(Restrictions.lt("price", 2000)); // To get records having productName starting with criteriaite criteria.add(Restrictions.like("productName", "criteriaite%")); // Case sensitive form of the above restriction. criteria.add(Restrictions.ilike("productName", "zara%")); // To get records having price in between 1000 and 2000 criteria.add(Restrictions.between("price", 1000, 2000)); // To check if the given property price is null criteria.add(Restrictions.isNull("price")); // To check if the given property is not null criteria.add(Restrictions.isNotNull("price")); // To check if the given property price is empty criteria.add(Restrictions.isEmpty("price")); // To check if the given property price is not empty criteria.add(Restrictions.isNotEmpty("price")); List results = criteria.list(); Pagination using Hibernate Criteria By using criteria methods setFirstResult() and setMaxResults() we can achieve pagination concept. Criteria criteria = session.createCriteria(Product.class); criteria.setMaxResults(10); criteria.setFirstResult(20); Projections class in Hibernate public final class Projections extends Object By Using org.hibernate.criterion.Projections class methods we can perform operations like minimum , maximum, average , sum and count. Hibernate Criteria query example using Projection class Criteria criteria = session.criteriaeateCriteria(Product.class); // To get total row count. criteria.setProjection(Projections.rowCount()); // To get average price. criteria.setProjection(Projections.avg("price")); // To get distinct countof name criteria.setProjection(Projections.countDistinct("name")); // To get maximum price criteria.setProjection(Projections.max("price")); // To get minimum price criteria.setProjection(Projections.min("price")); // To get sum of price criteria.setProjection(Projections.sum("price"))
Read: Hibernate Criteria Query Language (HCQL)
Previous Topic
