Hibernate常用方法之_查询

1、使用session的get方法

    public User getUser(int id){
        Session session = null;
        User user = null;
        try {
            session = HibernateUtils.getSession();
            /*根据主键获取一条记录*/
            user = (User) session.get(User.class,id);
        }finally {
            if (session != null){
                session.close();
            }
        }
        return user;
    }

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2、使用HQL语言查询 Query

    public User getUserBynName(String name){
        User user = null;
        Session session = null;
        try {
            session = HibernateUtils.getSession();
            /*这里查的是User对象，不是user表，支持多态*/
            String hql = " FROM User as user WHERE user.name = :name ";
            Query query = session.createQuery(hql);
            query.setString("name",name);
            /*只返回一条记录，否则报错*/
            user = (User) query.uniqueResult();
        }finally {
            if (session != null){
                session.close();
            }
        }
        return user;
    }

    public List<User> getUsersByName(String name){
        List<User> users = null;
        Session session = null;
        try {
            session = HibernateUtils.getSession();
            /*这里查的是User对象，不是user表，支持多态*/
            String hql = " FROM User as user WHERE user.name LIKE :name ";
            Query query = session.createQuery(hql);
            query.setString("name",name+"%");
            query.setFirstResult(10);
            query.setMaxResults(5);
            users = query.list();
        }finally {
            if (session != null){
                session.close();
            }
        }
        return users;
    }

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3、使用条件查询 Criteria

    public User getUserByNameCri(String name){
        Session session = null;
        User user = null;
        try {
            session = HibernateUtils.getSession();
            /*条件查询*/
            Criteria criteria = session.createCriteria(User.class);
            /*添加约束条件*/
            criteria.add(Restrictions.eq("name",name));
            user = (User) criteria.uniqueResult();
        }finally {
            if (session != null){
                session.close();
            }
        }
        return user;
    }