问题描述
public static void main（String [] a）throws Exception {
Session sessione = HibernateUtil.getSessionFactory（）。openSession（）;
Query query = sessione.createSQLQuery（select * from User）。addEntity（User.class）;
列表<用户> rows = query.list（）;
Iterator it = rows.iterator（）; （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（））;
$ b $ p
$ b 这个函数能够连接并执行一个查询DB ...
我想创建相同的函数，但更一般...以前只针对一个表（ User ），新的必须能够接受查询的 String 参数作为输入，以及将执行查询的类类型。这将允许我只使用一行来执行查询。
它应该是这样的：
public static void queryResult（String query，< ClassOfTable>）{
Session sessione = HibernateUtil.getSessionFactory（）。openSession（）;
Query qy = sessione.createSQLQuery（query）.addEntity（< ClassOfTable> .class）;
列表<< ClassOfTable>> rows = qy.list（）;
Iterator it = rows.iterator（）;
while（it.hasNext（））{
< ClassOfTable> obj =（< ClassOfTable>）it.next（）;
}
}
在哪里找到 ClassOfTable 我不知道如何推广代码...
我希望已经清楚...
PS ClassOfTable 应该是DB中一个表的类（ Hibernate ）。
$
解决方案 public static< T> void queryResult（String query，Class< ;? extends T> clazz）{
Session session = HibernateUtil.getSessionFactory（）。openSession（）;
Query q = session.createSQLQuery（query）.addEntity（clazz）;
列出行= q.list（）;
Iterator it = rows.iterator（）; （it.hasNext（））{
T t =（T）it.next（）;
//做你的工作对象t
}
}
如果您的意图是返回结果集，请使用：
public static< T>列表与LT; T> queryResult（String query，Class< ;? extends T> clazz）{
Session session = HibernateUtil.getSessionFactory（）。openSession（）;
Query q = session.createSQLQuery（query）.addEntity（clazz）;
列表< T> rows =（List< T>）q.list（）;
返回Collections.unmodifiableList（rows）;
}
//现在调用泛型方法
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（））;
}）;
This is my basic function:
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());
}
This function is capable to connect and perform a query on my DB...
I want to create the same function but more general... The previous was specific for only one table (User), the new one must be able to accept as input a String parameter for the query, and the class type where the query will be executed. This will allow me to use only one row in order to perform a query.
It should be something like this:
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();
}
}
Where you find ClassOfTable I don't know how to "generalize" the code...
I hope to have been clear...
P.S. ClassOfTable should be the class rappresentative of a table in DB (Hibernate).
Thanks.
解决方案 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
}
}
If your intention is to return resultset, use:
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());
});
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