Java中的函数指针

发布于 2024-07-27 04:57:20 字数 1231 浏览 4 评论 0原文

我正在用 java 在 wicket 中编写一个登录页面，并希望将其编写得尽可能通用，因此我需要将一个函数传递给类，该函数在 C++ 中被称为函数指针。该类是：

class LoginForm extends Form
{

    public LoginForm(String id,TextField username,TextField password,WebResponse webResponse)
    {
        super(id);
    }

    @Override
    public void onSubmit()
    {
        String password = Login.this.getPassword();
        String userId = Login.this.getUserId();
        String role = authenticate(userId, password);
        if (role != null)
        {
            if (Login.this.getSave())
            {
                utilities.CreateCookie("Username", userId, false, 1209600, (WebResponse) getRequestCycle().getResponse());
                utilities.CreateCookie("Password", password, false, 1209600, (WebResponse) getRequestCycle().getResponse());
            }
            User loggedInUser = new User(userId, role);
            WiaSession session = (WiaSession) getSession();
            session.setUser(loggedInUser);
            if (!continueToOriginalDestination())
            {
                setResponsePage(UserHome.class);
            }
        }
        else
        {
            wrongUserPass.setVisible(true);
        }
    }
}

验证该函数在哪里我应该做什么？

原文

I'm writing a Login page in wicket by java and want to write it as general as possible so I need to pass to class a function which famous as Function Pointer in C++.
The class is:

class LoginForm extends Form
{

    public LoginForm(String id,TextField username,TextField password,WebResponse webResponse)
    {
        super(id);
    }

    @Override
    public void onSubmit()
    {
        String password = Login.this.getPassword();
        String userId = Login.this.getUserId();
        String role = authenticate(userId, password);
        if (role != null)
        {
            if (Login.this.getSave())
            {
                utilities.CreateCookie("Username", userId, false, 1209600, (WebResponse) getRequestCycle().getResponse());
                utilities.CreateCookie("Password", password, false, 1209600, (WebResponse) getRequestCycle().getResponse());
            }
            User loggedInUser = new User(userId, role);
            WiaSession session = (WiaSession) getSession();
            session.setUser(loggedInUser);
            if (!continueToOriginalDestination())
            {
                setResponsePage(UserHome.class);
            }
        }
        else
        {
            wrongUserPass.setVisible(true);
        }
    }
}

where authenticate is that function what should I do?

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韶华倾负 2024-08-03 04:57:20

只需传递一个定义authenticate方法的接口即可。

void DoSomething(IAuthenticationProvider authProvider) {
    // ...
    authProvider.authenticate();
}

Just pass an Interface which defines the authenticate method.

void DoSomething(IAuthenticationProvider authProvider) {
    // ...
    authProvider.authenticate();
}

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街角卖回忆 2024-08-03 04:57:20

您可以使用内部类

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酷到爆炸 2024-08-03 04:57:20

在java中没有任何东西称为函数指针，而是函数对象。在此您可以定义其方法对其他对象执行操作的对象。例如，

 class MyClass 
 {
      public void myFunction(String s1, String s2)
      { 
           return s1.length() - s2.length();
      }
 }

 MyClass m = new MyClass(); 
 m.myFunction("nnnnnn", "mmmmmmmmmmm");

这只不过是函数对象。如果我们遵循代码接口规则，那么我们就可以定义接口并且也可以使用泛型。

 public interface MyInterface<T>
 {
      public void myFunction(T s1, T s2);
 }

现在原来的类可以实现这个接口了。上面的例子只是Comparator接口例子的简单修改。如果您不需要具体类，也可以使用匿名类。

Arrays.sort(stringArray, new Comparator <String> ()
  {
       public int compare(String s1, String s2)
             {
                   return s1.length() - s2.length();
             }
  };
  );

希望能帮助到你。

In java there is nothing call function pointer rather it is function object. In this you can define object whose methods performs operation on the other objects. e.g.

 class MyClass 
 {
      public void myFunction(String s1, String s2)
      { 
           return s1.length() - s2.length();
      }
 }

 MyClass m = new MyClass(); 
 m.myFunction("nnnnnn", "mmmmmmmmmmm");

This is nothing but function object. If we follow code to interface rule then we can define an interface and can use generics as well.

 public interface MyInterface<T>
 {
      public void myFunction(T s1, T s2);
 }

Now the original class can implement this interface. The above example is just a simple modification of Comparator interface example. If you don't want concrete class you can use anonymous class as well.

Arrays.sort(stringArray, new Comparator <String> ()
  {
       public int compare(String s1, String s2)
             {
                   return s1.length() - s2.length();
             }
  };
  );

Hope it helps.

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