Authenticator (Java Platform SE 8 )
Keywords: java.net.Authenticator class
Date: 2026-04-17

compact1, compact2, compact3
java.net

## Class Authenticator

- java.lang.Object
- - java.net.Authenticator

-     public abstract class Authenticator
      extends Object

  The class Authenticator represents an object that knows how to obtain authentication for a network connection. Usually, it will do this by prompting the user for information.

  Applications use this class by overriding `getPasswordAuthentication()` in a sub-class. This method will typically use the various getXXX() accessor methods to get information about the entity requesting authentication. It must then acquire a username and password either by interacting with the user or through some other non-interactive means. The credentials are then returned as a `PasswordAuthentication` return value.

  An instance of this concrete sub-class is then registered with the system by calling `setDefault(Authenticator)`. When authentication is required, the system will invoke one of the requestPasswordAuthentication() methods which in turn will call the getPasswordAuthentication() method of the registered object.

  All methods that request authentication have a default implementation that fails.

  Since:
    1.2
  See Also:
    `setDefault(java.net.Authenticator)`, `getPasswordAuthentication()`

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `Authenticator.RequestorType` The type of the entity requesting authentication.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Authenticator()`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected PasswordAuthentication` | `getPasswordAuthentication()` Called when password authorization is needed.
    `protected String` | `getRequestingHost()` Gets the `hostname` of the site or proxy requesting authentication, or `null` if not available.
    `protected int` | `getRequestingPort()` Gets the port number for the requested connection.
    `protected String` | `getRequestingPrompt()` Gets the prompt string given by the requestor.
    `protected String` | `getRequestingProtocol()` Give the protocol that's requesting the connection.
    `protected String` | `getRequestingScheme()` Gets the scheme of the requestor (the HTTP scheme for an HTTP firewall, for example).
    `protected InetAddress` | `getRequestingSite()` Gets the `InetAddress` of the site requesting authorization, or `null` if not available.
    `protected URL` | `getRequestingURL()` Returns the URL that resulted in this request for authentication.
    `protected Authenticator.RequestorType` | `getRequestorType()` Returns whether the requestor is a Proxy or a Server.
    `static PasswordAuthentication` | `requestPasswordAuthentication(InetAddress addr, int port, String protocol, String prompt, String scheme)` Ask the authenticator that has been registered with the system for a password.
    `static PasswordAuthentication` | `requestPasswordAuthentication(String host, InetAddress addr, int port, String protocol, String prompt, String scheme)` Ask the authenticator that has been registered with the system for a password.
    `static PasswordAuthentication` | `requestPasswordAuthentication(String host, InetAddress addr, int port, String protocol, String prompt, String scheme, URL url, Authenticator.RequestorType reqType)` Ask the authenticator that has been registered with the system for a password.
    `static void` | `setDefault(Authenticator a)` Sets the authenticator that will be used by the networking code when a proxy or an HTTP server asks for authentication.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### Authenticator

          public Authenticator()

  - ### Method Detail

    - #### setDefault

          public static void setDefault(Authenticator a)

      Sets the authenticator that will be used by the networking code when a proxy or an HTTP server asks for authentication.

      First, if there is a security manager, its `checkPermission` method is called with a `NetPermission("setDefaultAuthenticator")` permission. This may result in a java.lang.SecurityException.

      Parameters:
        `a` - The authenticator to be set. If a is `null` then any previously set authenticator is removed.
      Throws:
        `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow setting the default authenticator.
      See Also:
        `SecurityManager.checkPermission(java.security.Permission)`, `NetPermission`

    - #### requestPasswordAuthentication

          public static PasswordAuthentication requestPasswordAuthentication(InetAddress addr,
                                                                             int port,
                                                                             String protocol,
                                                                             String prompt,
                                                                             String scheme)

      Ask the authenticator that has been registered with the system for a password.

      First, if there is a security manager, its `checkPermission` method is called with a `NetPermission("requestPasswordAuthentication")` permission. This may result in a java.lang.SecurityException.

      Parameters:
        `addr` - The InetAddress of the site requesting authorization, or null if not known.
        `port` - the port for the requested connection
        `protocol` - The protocol that's requesting the connection (`getRequestingProtocol()`)
        `prompt` - A prompt string for the user
        `scheme` - The authentication scheme
      Returns:
        The username/password, or null if one can't be gotten.
      Throws:
        `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow the password authentication request.
      See Also:
        `SecurityManager.checkPermission(java.security.Permission)`, `NetPermission`

    - #### requestPasswordAuthentication

          public static PasswordAuthentication requestPasswordAuthentication(String host,
                                                                             InetAddress addr,
                                                                             int port,
                                                                             String protocol,
                                                                             String prompt,
                                                                             String scheme)

      Ask the authenticator that has been registered with the system for a password. This is the preferred method for requesting a password because the hostname can be provided in cases where the InetAddress is not available.

      First, if there is a security manager, its `checkPermission` method is called with a `NetPermission("requestPasswordAuthentication")` permission. This may result in a java.lang.SecurityException.

      Parameters:
        `host` - The hostname of the site requesting authentication.
        `addr` - The InetAddress of the site requesting authentication, or null if not known.
        `port` - the port for the requested connection.
        `protocol` - The protocol that's requesting the connection (`getRequestingProtocol()`)
        `prompt` - A prompt string for the user which identifies the authentication realm.
        `scheme` - The authentication scheme
      Returns:
        The username/password, or null if one can't be gotten.
      Throws:
        `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow the password authentication request.
      Since:
        1.4
      See Also:
        `SecurityManager.checkPermission(java.security.Permission)`, `NetPermission`

    - #### requestPasswordAuthentication

          public static PasswordAuthentication requestPasswordAuthentication(String host,
                                                                             InetAddress addr,
                                                                             int port,
                                                                             String protocol,
                                                                             String prompt,
                                                                             String scheme,
                                                                             URL url,
                                                                             Authenticator.RequestorType reqType)

      Ask the authenticator that has been registered with the system for a password.

      First, if there is a security manager, its `checkPermission` method is called with a `NetPermission("requestPasswordAuthentication")` permission. This may result in a java.lang.SecurityException.

      Parameters:
        `host` - The hostname of the site requesting authentication.
        `addr` - The InetAddress of the site requesting authorization, or null if not known.
        `port` - the port for the requested connection
        `protocol` - The protocol that's requesting the connection (`getRequestingProtocol()`)
        `prompt` - A prompt string for the user
        `scheme` - The authentication scheme
        `url` - The requesting URL that caused the authentication
        `reqType` - The type (server or proxy) of the entity requesting authentication.
      Returns:
        The username/password, or null if one can't be gotten.
      Throws:
        `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow the password authentication request.
      Since:
        1.5
      See Also:
        `SecurityManager.checkPermission(java.security.Permission)`, `NetPermission`

    - #### getRequestingHost

          protected final String getRequestingHost()

      Gets the `hostname` of the site or proxy requesting authentication, or `null` if not available.
      Returns:
        the hostname of the connection requiring authentication, or null if it's not available.
      Since:
        1.4

    - #### getRequestingSite

          protected final InetAddress getRequestingSite()

      Gets the `InetAddress` of the site requesting authorization, or `null` if not available.
      Returns:
        the InetAddress of the site requesting authorization, or null if it's not available.

    - #### getRequestingPort

          protected final int getRequestingPort()

      Gets the port number for the requested connection.
      Returns:
        an `int` indicating the port for the requested connection.

    - #### getRequestingProtocol

          protected final String getRequestingProtocol()

      Give the protocol that's requesting the connection. Often this will be based on a URL, but in a future JDK it could be, for example, "SOCKS" for a password-protected SOCKS5 firewall.
      Returns:
        the protocol, optionally followed by "/version", where version is a version number.
      See Also:
        `URL.getProtocol()`

    - #### getRequestingPrompt

          protected final String getRequestingPrompt()

      Gets the prompt string given by the requestor.
      Returns:
        the prompt string given by the requestor (realm for http requests)

    - #### getRequestingScheme

          protected final String getRequestingScheme()

      Gets the scheme of the requestor (the HTTP scheme for an HTTP firewall, for example).
      Returns:
        the scheme of the requestor

    - #### getPasswordAuthentication

          protected PasswordAuthentication getPasswordAuthentication()

      Called when password authorization is needed. Subclasses should override the default implementation, which returns null.
      Returns:
        The PasswordAuthentication collected from the user, or null if none is provided.

    - #### getRequestingURL

          protected URL getRequestingURL()

      Returns the URL that resulted in this request for authentication.
      Returns:
        the requesting URL
      Since:
        1.5

    - #### getRequestorType

          protected Authenticator.RequestorType getRequestorType()

      Returns whether the requestor is a Proxy or a Server.
      Returns:
        the authentication type of the requestor
      Since:
        1.5

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