一尘不染

Java类-如何将泛型对象传递给函数

hibernate

这是我的基本功能:

public static void main(String[] a) throws Exception {

    Session sessione = HibernateUtil.getSessionFactory().openSession();
    Query query = sessione.createSQLQuery("select * from User").addEntity(User.class);
    List<User> rows = query.list();
    Iterator it = rows.iterator();
    while (it.hasNext()) {
        User usr = (User) it.next();
        System.out.println(usr.getEmail());
        System.out.println(usr.getName());
        System.out.println(usr.getIdUser());
        System.out.println(usr.getUser());

    }

此功能能够连接并在我的数据库上执行查询…

我想创建相同的功能,但更通用。…前一个仅用于一个表(User),新表必须能够接受String查询的参数作为输入,以及将在其中执行查询的类类型。这将允许我仅使用一行来执行查询。

应该是这样的:

public static void queryResult(String query, <ClassOfTable>) {

    Session sessione = HibernateUtil.getSessionFactory().openSession();
    Query qy = sessione.createSQLQuery(query).addEntity(<ClassOfTable>.class);
    List<<ClassOfTable>> rows = qy.list();
    Iterator it = rows.iterator();
    while (it.hasNext()) {
        <ClassOfTable> obj = (<ClassOfTable>) it.next();
    }

}

您发现ClassOfTable我不知道如何“通用”代码…

我希望已经清楚了…

PS ClassOfTable应该是DB(Hibernate)中表的类的代表。

谢谢。


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2020-06-20

共1个答案

一尘不染

public static <T> void queryResult(String query, Class<? extends T> clazz) {
    Session session = HibernateUtil.getSessionFactory().openSession();
    Query q = session.createSQLQuery(query).addEntity(clazz);
    List rows = q.list();
    Iterator it = rows.iterator();
    while (it.hasNext()) {
        T t = (T) it.next();
        // do your work on object t
    }
}

如果您打算返回结果集,请使用:

public static <T> List<T> queryResult(String query, Class<? extends T> clazz) {
    Session session = HibernateUtil.getSessionFactory().openSession();
    Query q = session.createSQLQuery(query).addEntity(clazz);
    List<T> rows = (List<T>) q.list();
    return Collections.unmodifiableList(rows);
}

// now call generic method
List<User> users = queryResult("select * from User", User.class);
users.forEach(usr -> {
    System.out.println(usr.getEmail());
    System.out.println(usr.getName());
    System.out.println(usr.getIdUser());
    System.out.println(usr.getUser());
});
2020-06-20