java SSH第一章学习内容（HQL查询）

HQL：查询日志 8个例子

例子准备工作
1.先自动生成实体类以及DAO类
2.创建一个HqlSelect类继承UserDAO，用于直接调用Session使用
3.测试类调用HqlSelect类方法
java SSH第一章学习内容（HQL查询）
注意：query.uniqueResult().toString()使用查询一行数据，query.list()结果集的数据
q.setInteger(1, 10); mysql坐标从1开始，oracle从0开始

1.查询所有(对象类型)

public List<String> findAll2(){
       Session session =super.getSession();
       String hql="select u.uname from User u";
       Query q = session.createQuery(hql);       //执行SQL语句
       List<String> it = q.list();               //使用Qurey.list返回集合
       for (String it2:it) {
           System.out.println(it2);
       }
       return it;
   }

2.查询部分(String类型)
   public List<String> findAll2(){
       Session session =super.getSession();
       String hql="select u.uname from User u";
       Query q = session.createQuery(hql);       //执行SQL语句
       List<String> it = q.list();               //使用Qurey.list返回String集合
       for (String it2:it) {
           System.out.println(it2);
       }
       return it;
   }

3.查询两列(Object类型)
   public List<Object> findAll3(){
       Session session =super.getSession();
       String hql="select u.uname,u.upwd from User u";
       Query q = session.createQuery(hql);
       List<Object> objs = q.list();
       for (Object obj:objs) {
           Object[] obj2=(Object[]) obj;
           System.out.println(obj2[0]);
           System.out.println(obj2[1]);
       }
       return objs;
   }

4.参数查询
   public List<User> findAll4(){
       Session session=super.getSession();
       String sql="from User u where u.uid=?";
       Query q= session.createQuery(sql);
       q.setInteger(1,2);
       List<User>it = q.list();
       for (User it2:it) {
           System.out.println(it2.getUname()+it2.getUpwd());
       }
       return it;
   }

5.命名查询
   public List<User> findAll5(){
       Session session=super.getSession();
       String sql="from User u where u.uid=:a";
       Query q= session.createQuery(sql);
       q.setInteger("a",3);
       List<User>it = q.list();
       for (User it2:it) {
           System.out.println(it2.getUname()+it2.getUpwd());
       }
       return it;
   }

6.查询结果只返回一个值
   public int findall6(){
       Session session=super.getSession();
       String sql="select count(u) from User u";
       Query q = session.createQuery(sql);
       int count=Integer.parseInt(q.uniqueResult().toString());
       System.out.println(count);
       return count;
   }

7.查询结果一行数据
   public int findall7(){
       Session session=super.getSession();
       String sql="select count(u) from User u where u.uid=:uid";
       Query q = session.createQuery(sql);
       q.setInteger("uid", 10);
       int count=Integer.parseInt(q.uniqueResult().toString());
       System.out.println(count);
       return count;
   }

8.分页查询
   public List<User> findall8(int num1,int num2){
       Session session=super.getSession();
       String sql="from User u";
       Query q = session.createQuery(sql);
       q.setFirstResult((num1-1)*num2);
       q.setMaxResults(num2);
       List<User> li = q.list();
       for (User l:li) {
           System.out.println(l.getUname()+l.getUpwd());
       }
       return li;
   }

参考代码：

HqlSelect类

public class HqlSelect extends UserDAO{
   //查询所有(对象类型)
   public List<User>findAll(){
       Session session=super.getSession();
       String hql="from User";
       Query query=session.createQuery(hql);
       List<User> it = query.list();
       for (User it1:it) {
           System.out.println(it1.getUid()+it1.getUname()+it1.getUpwd());
       }
       return it;
   }
   //查询部分(String类型)
   public List<String> findAll2(){
       Session session =super.getSession();
       String hql="select u.uname from User u";
       Query q = session.createQuery(hql);       //执行SQL语句
       List<String> it = q.list();               //使用Qurey.list返回集合
       for (String it2:it) {
           System.out.println(it2);
       }
       return it;
   }
   //查询两列(Object类型)
   public List<Object> findAll3(){
       Session session =super.getSession();
       String hql="select u.uname,u.upwd from User u";
       Query q = session.createQuery(hql);
       List<Object> objs = q.list();
       for (Object obj:objs) {
           Object[] obj2=(Object[]) obj;
           System.out.println(obj2[0]);
           System.out.println(obj2[1]);
       }
       return objs;
   }
   //参数查询
   public List<User> findAll4(){
       Session session=super.getSession();
       String sql="from User u where u.uid=?";
       Query q= session.createQuery(sql);
       q.setInteger(1,2);
       List<User>it = q.list();
       for (User it2:it) {
           System.out.println(it2.getUname()+it2.getUpwd());
       }
       return it;
   }
   //命名查询
   public List<User> findAll5(){
       Session session=super.getSession();
       String sql="from User u where u.uid=:a";
       Query q= session.createQuery(sql);
       q.setInteger("a",3);
       List<User>it = q.list();
       for (User it2:it) {
           System.out.println(it2.getUname()+it2.getUpwd());
       }
       return it;
   }
   //查询结果只返回一个值
   public int findall6(){
       Session session=super.getSession();
       String sql="select count(u) from User u";
       Query q = session.createQuery(sql);
       int count=Integer.parseInt(q.uniqueResult().toString());
       System.out.println(count);
       return count;
   }
   //查询结果一行数据
   public int findall7(){
       Session session=super.getSession();
       String sql="select count(u) from User u where u.uid=:uid";
       Query q = session.createQuery(sql);
       q.setInteger("uid", 10);
       int count=Integer.parseInt(q.uniqueResult().toString());
       System.out.println(count);
       return count;
   }
   //分页查询
   public List<User> findall8(int num1,int num2){
       Session session=super.getSession();
       String sql="from User u";
       Query q = session.createQuery(sql);
       q.setFirstResult((num1-1)*num2);
       q.setMaxResults(num2);
       List<User> li = q.list();
       for (User l:li) {
           System.out.println(l.getUname()+l.getUpwd());
       }
       return li;
   }
}

java SSH第一章学习内容（HQL查询）

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