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This article mainly introduces the Criteria query sentence example analysis, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor with you to understand.

Criteria query

Package com.shiryu.otm; import java.util.Iterator; import java.util.List; import org.hibernate.Criteria; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.DetachedCriteria; import org.hibernate.criterion.Expression; import org.hibernate.criterion.Order; import org.hibernate.criterion.Projections; import org.hibernate.criterion.Subqueries Public class Test2 {public static void main (String args []) {SessionFactory factory = new Configuration (). Configure (). BuildSessionFactory (); Session session = factory.openSession (); Transaction tr = session.beginTransaction (); / / Criteria query statement supplement / / one, compound query / / in this one-to-many example. We use a composite query to query all users and their addresses. / / Criteria criteria = session.createCriteria (User.class); / / List list = criteria.list (); / for (int I = 0; I

< list.size(); i++) { // User user = (User) list.get(i); // System.out.println("\t user:"+i+" name is:" + user.getName()); // // Set addrSet = user.getAddresses(); // Iterator it = addrSet.iterator(); // while(it.hasNext()){ // Address addr = (Address)it.next(); // System.out.println("\t\t user:"+i+" address is:"+addr.getAddress()); // } // } // 通过Criteria查询条件，我们可以查询位于上海的用户 // Criteria criteria = session.createCriteria(User.class); // // Criteria addCriteria = // criteria.createCriteria("addresses");//这里addresses和User类对应 // addCriteria.add(Expression.like("address", // "%shanghai%"));//这里构造新的Criteria查询过滤条件 // List list = criteria.list(); // // for (int i = 0; i < list.size(); i++) { // User user = (User) list.get(i); // System.out.println("\t user:" + i + " name is:" + user.getName()); // // Set addrSet = user.getAddresses(); // Iterator it = addrSet.iterator(); // while (it.hasNext()) { // Address addr = (Address) it.next(); // System.out.println("\t\t user:" + i + " address is:" // + addr.getAddress()); // } // } /* * 二、DetachedCriteria的使用 hibernate2 中critria * 生命周期位于宿主Session生命周期之内，session创建criteria实例，Session被销毁，critria实例也随之失效 * 这很大程度上限制了criteria的重用hibernate3 中提供了DetachedCriteria * 它可以脱离Session实例独立存在，我们可以把通用的criteria查询条件进行抽离，更好的实现代码重用 */ DetachedCriteria deCriteria = DetachedCriteria.forClass(User.class); deCriteria.add(Expression.eq("name", "zhaiyu")); deCriteria.add(Expression.eq("age", new Integer(21))); Criteria criteria = deCriteria.getExecutableCriteria(session);// 在其需要的时候与session进行绑定 Iterator it = criteria.list().iterator(); while (it.hasNext()) { User user = (User) it.next(); System.out.println(user.getName()); } /* * DetachedCriteria 也可以用于子查询表达 下例返回了年龄超过了平均值的用户记录 */ DetachedCriteria avgAge = DetachedCriteria.forClass(User.class); avgAge.setProjection(Projections.avg("age")); Criteria criteria2 = session.createCriteria(User.class); criteria2.add(Subqueries.propertyGt("age", avgAge)); List list = criteria2.list(); // 我们可以将DetachedCriteria纳入查询表达式 :select ... from User where age >

(select / / avg (age) from User) / / (select avg (age) from User) described by DetachedCriteria avgAge / * III. Advanced features of Criteria query statements * / / limit the range of returned records Criteria criteria3 = session.createCriteria (User.class); / / limit 20 records criteria3.setFirstResult (100) starting from Article 100 Criteria3.setMaxResults (20); / / sort records Criteria criteria4 = session.createCriteria (User.class); criteria4.add (Expression.eq ("id", new Integer (2)); criteria4.addOrder (Order.asc ("name")); criteria4.addOrder (Order.desc ("id")) / * Criteria grouping and statistics * / Criteria criteria5 = session.createCriteria (User.class); criteria5.setProjection (Projections.groupProperty ("age")); Iterator it3 = criteria5.list () .iterator (); while (it.hasNext ()) {System.out.println (it.next ()) } Thank you for reading this article carefully. I hope the article "sample Analysis of Criteria query sentences" shared by the editor will be helpful to you. At the same time, I also hope that you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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