欢迎使用Hibernate Criteria示例教程。
今天，我们将研究Hibernate 中的条件。

Hibernate 标准

在大多数情况下，我们使用HQL来查询数据库并获取结果。
HQL不是更新或者删除值的首选方法，因为这样我们就需要注意表之间的任何关联。

Hibernate Criteria API提供了面向对象的方法来查询数据库并获取结果。
我们无法使用Hibernate中的条件来运行更新或者删除查询或者任何DDL语句。
Hibernate Criteria查询仅用于使用面向对象方法从数据库中获取结果。

对于我的Hibernate标准示例，我将使用与我的HQL示例相同的设置，并向您展示如何在Hibernate中使用Criteria来查询数据库。

Hibernate Criteria API的一些常见用法是：

• Hibernate Criteria API提供了Projection，我们可以将其用于聚合函数，例如sum()，min()，max()等。

• Hibernate Criteria API可以与ProjectionList一起使用，以仅获取选定的列。

• Hibernate中的条件可以通过联接多个表来用于联接查询，Hibernate条件联接的有用方法是createAlias()，setFetchMode()和setProjection()

• Hibernate API中的条件可用于获取有条件的结果，有用的方法是add()，我们可以其中添加限制。

• Hibernate Criteria API提供了addOrder()方法，可用于对结果进行排序。

下面的类展示了Hibernate Criteria API的不同用法，其中大多数是HQL教程中示例的替代。

package com.theitroad.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.theitroad.hibernate.model.Employee;
import com.theitroad.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();
	}

}

当我们执行上面的Hibernate Criteria示例程序时，我们得到以下输出。

Jan 26, 2014 6:53:32 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
Jan 26, 2014 6:53:32 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.5.Final}
Jan 26, 2014 6:53:32 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
Jan 26, 2014 6:53:32 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Jan 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration configure
INFO: HHH000043: Configuring from resource: hibernate.cfg.xml
Jan 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: HHH000040: Configuration resource: hibernate.cfg.xml
Jan 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!
Jan 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration doConfigure
INFO: HHH000041: Configured SessionFactory: null
Hibernate Configuration loaded
Hibernate serviceRegistry created
Jan 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!)
Jan 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]
Jan 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000046: Connection properties: {user=hyman, password=}
Jan 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000006: Autocommit mode: false
Jan 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Jan 26, 2014 6:53:32 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
Jan 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
Jan 26, 2014 6:53:32 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
Jan 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
[hyman, San Jose]
[David, Santa Clara]
[Lisa, Bangalore]
[Hyman, New Delhi]
Jan 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost/TestDB]

由于我使用的是HQL示例项目，因此您需要导入该项目，然后添加此类以使其正常工作。