Java中的Java.net.Authenticator类

原文:https://www . geesforgeks . org/Java-net-authenticator-class-Java/

认证器类用于需要认证才能访问某个网址的情况。一旦知道需要进行身份验证，它就会提示用户输入相同的内容，或者使用一些硬编码的用户名和密码。
要使用该类，请遵循以下步骤-

1. 创建一个扩展验证器的类。让我们将其命名为 customAuth。


2. 重写 getPasswordAuthentication()方法。此方法包含获取请求身份验证的实体的详细信息的几种方法。所有这些方法将在后面详细讨论。



3. Set the newly created subclass as the default authenticator to be used when a http server asks for authentcation, with setDefault(Authenticator a) method of Authenticator class.

   方法:

   
   

   1. 设置默认值(认证者 a) : 设置当 HTTP 服务器需要认证时使用的认证者。

      ```java
      Syntax : public static void setDefault(Authenticator a)
      throws SecurityException
      Parameter :
      a : authenticator to be set as default
      Throws :
      SecurityException : if security manager doesn't allow
      setting default authenticator

      ```

   
   

   2. requestPasswordAuthentication() : Asks the authenticator registered with the system for password. Returns username/password or null if not found.

      ```java
      Syntax :
      public static PasswordAuthentication requestPasswordAuthentication(
      InetAddress addr,
      int port,
      String protocol,
      String prompt,
      String scheme)
      Parameter :
      addr : Inet address of the site asking for authentication
      port : port of requesting site
      protocol : protocol used for connection
      prompt : message for the user
      scheme : authentication scheme
      Throws :
      SecurityException : if security manager doesn't allow
      setting password authentication.

      ```

      另一种重载方法，可以在 inetaddress 不可用时使用主机名的情况下使用。

      ```java
      Syntax :
      public static PasswordAuthentication requestPasswordAuthentication(
      String host,
      InetAddress addr,
      int port,
      String protocol,
      String prompt,
      String scheme)
      Parameter :
      host : hostname of the site asking for authentication
      addr : Inet address of the site asking for authentication
      port : port of requesting site
      protocol : protocol used for connection
      prompt : message for the user
      scheme : authentication scheme
      Throws :
      SecurityException : if security manager doesn't allow
      setting password authentication.

      ```

      另一种重载方法，如果请求身份验证的站点的 URL 是已知的，而不是地址和主机名，则可以使用这种方法。

      ```java
      Syntax :
      public static PasswordAuthentication requestPasswordAuthentication(
      String host,
      InetAddress addr,
      int port,
      String protocol,
      String prompt,
      URL url,
      String scheme)
      Parameter :
      host : hostname of the site asking for authentication
      addr : Inet address of the site asking for authentication
      port : port of requesting site
      protocol : protocol used for connection
      prompt : message for the user
      url : URL of the site requesting authentication
      scheme : authentication scheme
      Throws :
      SecurityException : if security manager doesn't allow
      setting password authentication.

      ```

   
   

   3. getRequestingHost() :返回请求身份验证的站点的主机名。

      ```java
      Syntax : protected final String getRequestingHost()

      ```

   
   

   4. getRequestingSite() :返回请求认证的站点的地址。

      ```java
      Syntax : protected final InetAddress getRequestingSite()

      ```

   
   

   5. getRequestingPort() :返回连接的端口。

      ```java
      Syntax : protected final int getRequestingPort()

      ```

   
   

   6. getRequestingProtocol() :返回请求连接的协议。

      ```java
      Syntax : protected final String getRequestingProtocol()

      ```

   
   

   7. getrequestingrompt():返回请求者提示的消息。

      ```java
      Syntax : protected final String getRequestingPrompt()

      ```

   
   

   8. getRequestingScheme() :返回请求站点的方案。

      ```java
      Syntax : protected final String getRequestingScheme()

      ```

   
   

   9. getpassword authentication():需要密码验证时调用此方法。所有子类都必须重写此方法，因为默认方法总是返回 null。

      ```java
      Syntax : protected PasswordAuthentication getPasswordAuthentication()

      ```

   
   

   10. getRequestingURL() :返回请求者的 URL。

       ```java
       Syntax : protected final URL getRequestingURL()

       ```

   
   

   11. getRequestorType() :如果请求者是代理或者服务器，返回。

       ```java
       Syntax : protected Authenticator.RequestorType getRequestorType()

       ```

   
   

   Java 实现:

   ```java
   import java.io.BufferedReader;
   import java.io.IOException;
   import java.io.InputStreamReader;
   import java.net.Authenticator;
   import java.net.InetAddress;
   import java.net.MalformedURLException;
   import java.net.PasswordAuthentication;
   import java.net.URL;

   public class javanetauthenticator 
   {
       public static void main(String[] args) 
       {

   try {

   // setDefault() method
               // Sets the authenticator that will be used by the networking code
               // when a proxy or an HTTP server asks for authentication.
               Authenticator.setDefault(new CustomAuthenticator());

   URL url = new URL("http://securedwebsite.co.in/index.htm");

   // read text returned by server
               BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));

   String line;
               while ((line = in.readLine()) != null) {
                   System.out.println(line);
               }
               in.close();

   } catch (MalformedURLException e) {
               System.out.println("Malformed URL: " + e.getMessage());
           } catch (IOException e) {
               System.out.println("I/O Error: " + e.getMessage());
           }

   }

   public static class CustomAuthenticator extends Authenticator 
       {

   // getPasswordAuthentication() method
           // Called when password authorization is needed
           protected PasswordAuthentication getPasswordAuthentication() 
           {

   // requestPasswordAuthentication() method
               // uncomment this if default authenticator is registered with
               // the system
               // PasswordAuthentication pa=requestPasswordAuthentication
               // (inetaddr, port, protocol, prompt, scheme);

   // getRequestingPrompt() method
               String prompt = getRequestingPrompt();

   // getRequestingHost() method
               String hostname = getRequestingHost();

   // getRequestingSite() method
               InetAddress ipaddr = getRequestingSite();

   // getRequestingPort() method
               int port = getRequestingPort();

   // getRequestingProtocol() method
               String protocol = getRequestingProtocol();

   // getRequestingScheme() method
               String scheme = getRequestingScheme();

   // getRequestingURL() method
               URL u = getRequestingURL();

   // getRequestorType() method
               RequestorType rtype = getRequestorType();

   System.out.println("prompt:" + prompt);
               System.out.println("hostname:" + hostname);
               System.out.println("ipaddress:" + ipaddr);
               System.out.println("port:" + port);
               System.out.println("protocolo:" + protocol);
               System.out.println("scheme:" + scheme);
               System.out.println("URL:" + u);
               System.out.println("Requester Type:" + rtype);

   // hardcoded username and password to be used
               // this part can be replaced by an interactive code
               // to take uid and pwd form user
               String username = "admin";
               String password = "admin1";

   // Return the information (a data holder that is used by
               // Authenticator)
               return new PasswordAuthentication(username, password.toCharArray());

   }

   }
   }
   ```

   注意:这个程序只是为了解释 Authenticator 类程序的流程。程序中使用的网址是随机选择的，不代表任何实际的网址。这个程序只是展示了如何使用 Authenticator 类的方法。通过将网址更改为需要验证才能进入的服务器来测试该程序。

   参考: 官方 Java 文档

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