欢迎使用Hibernate标准示例教程。今天，我们将探讨Hibernate中的标准。
休眠条件
大多数时候，我们使用hql来查询数据库并获得结果。HQL不是更新或删除值的首选方式，因为这样我们就需要处理表之间的任何关联。Hibernate Criteria API为查询数据库和获取结果提供了面向对象的方法。我们不能在Hibernate中使用条件来运行UPDATE或DELETE查询或任何DDL语句。Hibernate标准查询只用于使用面向对象的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 Example中相同的设置，并向您展示如何在Hibernate中使用条件来查询数据库。Hibernate Criteria API的一些常见用法包括；
1.Hibernate Criteria API提供了可用于聚合函数的投影，如sum()、min()、max()等。
2.Hibernate Criteria API只能与ProjectionList配合使用，只能拉取选中的列。
3.Hibernate中的条件可以用于连接多个表的连接查询，Hibernate条件连接的有用方法有createAlias()、setFetchModel()和setProjection()
4.Hibernate API中的条件可以用于带条件的结果获取，有用的方法是Add()，我们可以在其中添加限制。
5.Hibernate Criteria API提供了addOrder()方法，我们可以使用该方法对结果进行排序。
下面的类展示了Hibernate Criteria API的不同用法，其中大多数是HQL教程中的示例的替换。
1package com.journaldev.hibernate.main;
2
3import java.util.Arrays;
4import java.util.List;
5
6import org.hibernate.Criteria;
7import org.hibernate.FetchMode;
8import org.hibernate.Session;
9import org.hibernate.SessionFactory;
10import org.hibernate.Transaction;
11import org.hibernate.criterion.Order;
12import org.hibernate.criterion.ProjectionList;
13import org.hibernate.criterion.Projections;
14import org.hibernate.criterion.Restrictions;
15
16import com.journaldev.hibernate.model.Employee;
17import com.journaldev.hibernate.util.HibernateUtil;
18
19public class HibernateCriteriaExamples {
20
21 @SuppressWarnings("unchecked")
22 public static void main(String[] args) {
23 // Prep work
24 SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
25 Session session = sessionFactory.getCurrentSession();
26 Transaction tx = session.beginTransaction();
27
28 //Get All Employees
29 Criteria criteria = session.createCriteria(Employee.class);
30 List<Employee> empList = criteria.list();
31 for(Employee emp : empList){
32 System.out.println("ID="+emp.getId()+", Zipcode="+emp.getAddress().getZipcode());
33 }
34
35 // Get with ID, creating new Criteria to remove all the settings
36 criteria = session.createCriteria(Employee.class)
37 .add(Restrictions.eq("id", new Long(3)));
38 Employee emp = (Employee) criteria.uniqueResult();
39 System.out.println("Name=" + emp.getName() + ", City="
40 + emp.getAddress().getCity());
41
42 //Pagination Example
43 empList = session.createCriteria(Employee.class)
44 .addOrder(Order.desc("id"))
45 .setFirstResult(0)
46 .setMaxResults(2)
47 .list();
48 for(Employee emp4 : empList){
49 System.out.println("Paginated Employees::"+emp4.getId()+","+emp4.getAddress().getCity());
50 }
51
52 //Like example
53 empList = session.createCriteria(Employee.class)
54 .add(Restrictions.like("name", "%i%"))
55 .list();
56 for(Employee emp4 : empList){
57 System.out.println("Employees having 'i' in name::"+emp4.getName()+","+emp4.getAddress().getCity());
58 }
59
60 //Projections example
61 long count = (Long) session.createCriteria(Employee.class)
62 .setProjection(Projections.rowCount())
63 .add(Restrictions.like("name", "%i%"))
64 .uniqueResult();
65 System.out.println("Number of employees with 'i' in name="+count);
66
67 //using Projections for sum, min, max aggregation functions
68 double sumSalary = (Double) session.createCriteria(Employee.class)
69 .setProjection(Projections.sum("salary"))
70 .uniqueResult();
71 System.out.println("Sum of Salaries="+sumSalary);
72
73 //Join example for selecting few columns
74 criteria = session.createCriteria(Employee.class, "employee");
75 criteria.setFetchMode("employee.address", FetchMode.JOIN);
76 criteria.createAlias("employee.address", "address"); // inner join by default
77
78 ProjectionList columns = Projections.projectionList()
79 .add(Projections.property("name"))
80 .add(Projections.property("address.city"));
81 criteria.setProjection(columns);
82
83 List<Object[]> list = criteria.list();
84 for(Object[] arr : list){
85 System.out.println(Arrays.toString(arr));
86 }
87
88
89 // Rollback transaction to avoid messing test data
90 tx.commit();
91 // closing hibernate resources
92 sessionFactory.close();
93 }
94
95}
当我们执行上面的休眠标准示例程序时，我们会得到以下输出。
1May 26, 2014 6:53:32 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
2INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
3May 26, 2014 6:53:32 PM org.hibernate.Version logVersion
4INFO: HHH000412: Hibernate Core {4.3.5.Final}
5May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment <clinit>
6INFO: HHH000206: hibernate.properties not found
7May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment buildBytecodeProvider
8INFO: HHH000021: Bytecode provider name : javassist
9May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration configure
10INFO: HHH000043: Configuring from resource: hibernate.cfg.xml
11May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration getConfigurationInputStream
12INFO: HHH000040: Configuration resource: hibernate.cfg.xml
13May 26, 2014 6:53:32 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity
14WARN: HHH000223: Recognized obsolete hibernate namespace https://hibernate.sourceforge.net/. Use namespace https://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!
15May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration doConfigure
16INFO: HHH000041: Configured SessionFactory: null
17Hibernate Configuration loaded
18Hibernate serviceRegistry created
19May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
20WARN: HHH000402: Using Hibernate built-in connection pool (not for production use!)
21May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
22INFO: HHH000401: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost/TestDB]
23May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
24INFO: HHH000046: Connection properties: {user=pankaj, password=****}
25May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
26INFO: HHH000006: Autocommit mode: false
27May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
28INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
29May 26, 2014 6:53:32 PM org.hibernate.dialect.Dialect <init>
30INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
31May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation
32INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4
33May 26, 2014 6:53:32 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
34INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
35May 26, 2014 6:53:32 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init>
36INFO: HHH000397: Using ASTQueryTranslatorFactory
37Hibernate: 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
38ID=1, Zipcode=95129
39ID=2, Zipcode=95051
40ID=3, Zipcode=560100
41ID=4, Zipcode=100100
42Hibernate: 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=?
43Name=Lisa, City=Bangalore
44Hibernate: 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 ?
45Paginated Employees::4,New Delhi
46Paginated Employees::3,Bangalore
47Hibernate: 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 ?
48Employees having 'i' in name::David,Santa Clara
49Employees having 'i' in name::Lisa,Bangalore
50Hibernate: select count(*) as y0_ from EMPLOYEE this_ where this_.emp_name like ?
51Number of employees with 'i' in name=2
52Hibernate: select sum(this_.emp_salary) as y0_ from EMPLOYEE this_
53Sum of Salaries=1000.0
54Hibernate: select this_.emp_name as y0_, address1_.city as y1_ from EMPLOYEE this_ inner join ADDRESS address1_ on this_.emp_id=address1_.emp_id
55[Pankaj, San Jose]
56[David, Santa Clara]
57[Lisa, Bangalore]
58[Jack, New Delhi]
59May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
60INFO: 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，然后添加此类才能使其工作。请注意输出中执行的hibernate查询，这样您就可以细化查询并获得所需的结果。以上就是对Hibernate中的Criteria的快速总结。