hibernate的查詢方式

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hibernate的查詢方式常見的主要分為三種: HQL, QBC（Query By Criteria）查詢, 以及使用原生SQL查詢

HQL查詢

• HQL（Hibernate Query Language）提供了豐富靈活的查詢方式，使用HQL進行查詢也是Hibernate官方推薦使用的查詢方式。

• HQL在文法結構上和SQL語句十分的相同，所以可以很快的上手進行使用。使用HQL需要用到Hibernate中的Query對象，該對象專門執行HQL方式的操作。

查詢所有樣本session.beginTransaction(); String hql = "from User"; // from 後跟的是要查詢的對象，而不是表Query query = session.createQuery(hql); List<User> userList = query.list(); for(User user:userList){   System.out.println(user.getUserName()); } session.getTransaction().commit();

擷取一個不完整的對象session.beginTransaction(); String hql = "select userName from User"; Query query = session.createQuery(hql); List nameList = query.list(); for(Object obj:nameList){   System.out.println(obj); } session.getTransaction().commit();// 多個屬性的話，需要用object[]接收session.beginTransaction(); String hql = "select userName,userPwd from User"; Query query = session.createQuery(hql); List nameList = query.list(); for(Object obj:nameList){     Object[] array = (Object[]) obj; // 轉成object[]    System.out.println("name:" + array[0]);     System.out.println("pwd:" + array[1]); } session.getTransaction().commit();

統計和分組查詢session.beginTransaction(); String hql = "select count(*),max(id) from User"; Query query = session.createQuery(hql); List nameList = query.list(); for(Object obj:nameList){     Object[] array = (Object[]) obj;     System.out.println("count:" + array[0]);     System.out.println("max:" + array[1]); } session.getTransaction().commit();

更多寫法select distinct name from Student;  select max(age) from Student;  select count(age),age from Student group by age;  from Student order by age;

HQL預留位置和分頁session.beginTransaction();        String sql ="select uname,password from User where enable=?";        Query query =session.createQuery(sql);        //預留位置內容        query.setBoolean(0, true);        //第幾個開始        query.setFirstResult(0);        //顯示個數        query.setMaxResults(2);        List<Object[]> list = query.list();                for (Object[] user : list) {            System.out.println(user[0]+"--"+user[1]);        }        session.getTransaction().commit();

原生SQL查詢

addEntity()樣本session.beginTransaction();  String sql = "select id,username,userpwd from t_user"; // addEntity()可以告訴Hibernate你想要封裝成對象的類型，然後自動為你封裝SQLQuery query = session.createSQLQuery(sql).addEntity(User.class);  List<User> list = query.list();  for(User user : list){   System.out.println(user.getUserName()); }  session.getTransaction().commit();

uniqueResult樣本session.beginTransaction();  String sql = "select id,username,userpwd from t_user where id = 2"; SQLQuery query = session.createSQLQuery(sql).addEntity(User.class);  User user = (User) query.uniqueResult();  System.out.println(user.getUserName());  session.getTransaction().commit();