Service (JavaMail API documentation)
Date: 2019-08-31

javax.mail

## Class Service

- java.lang.Object
- - javax.mail.Service

- Direct Known Subclasses:
    Store, Transport

      public abstract class Service
      extends java.lang.Object

  An abstract class that contains the functionality common to messaging services, such as stores and transports.

  A messaging service is created from a `Session` and is named using a `URLName`. A service must be connected before it can be used. Connection events are sent to reflect its connection status.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected boolean` | `debug` Debug flag for this service.
    `protected Session` | `session` The session from which this service was created.
    `protected URLName` | `url` The `URLName` of this service.

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `Service(Session session, URLName urlname)` Constructor.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addConnectionListener(ConnectionListener l)` Add a listener for Connection events on this service.
    `void` | `close()` Close this service and terminate its connection.
    `void` | `connect()` A generic connect method that takes no parameters.
    `void` | `connect(java.lang.String host, int port, java.lang.String user, java.lang.String password)` Similar to connect(host, user, password) except a specific port can be specified.
    `void` | `connect(java.lang.String user, java.lang.String password)` Connect to the current host using the specified username and password.
    `void` | `connect(java.lang.String host, java.lang.String user, java.lang.String password)` Connect to the specified address.
    `protected void` | `finalize()` Stop the event dispatcher thread so the queue can be garbage collected.
    `URLName` | `getURLName()` Return a URLName representing this service.
    `boolean` | `isConnected()` Is this service currently connected?
    `protected void` | `notifyConnectionListeners(int type)` Notify all ConnectionListeners.
    `protected boolean` | `protocolConnect(java.lang.String host, int port, java.lang.String user, java.lang.String password)` The service implementation should override this method to perform the actual protocol-specific connection attempt.
    `protected void` | `queueEvent(MailEvent event, java.util.Vector vector)` Add the event and vector of listeners to the queue to be delivered.
    `void` | `removeConnectionListener(ConnectionListener l)` Remove a Connection event listener.
    `protected void` | `setConnected(boolean connected)` Set the connection state of this service.
    `protected void` | `setURLName(URLName url)` Set the URLName representing this service.
    `java.lang.String` | `toString()` Return `getURLName.toString()` if this service has a URLName, otherwise it will return the default `toString`.

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

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

- - ### Field Detail

    - #### session

          protected Session session

      The session from which this service was created.

    - #### url

          protected URLName url

      The `URLName` of this service.

    - #### debug

          protected boolean debug

      Debug flag for this service. Set from the session's debug flag when this service is created.

  - ### Constructor Detail

    - #### Service

          protected Service(Session session,
                            URLName urlname)

      Constructor.
      Parameters:
        `session` - Session object for this service
        `urlname` - URLName object to be used for this service

  - ### Method Detail

    - #### connect

          public void connect()
                       throws MessagingException

      A generic connect method that takes no parameters. Subclasses can implement the appropriate authentication schemes. Subclasses that need additional information might want to use some properties or might get it interactively using a popup window.

      If the connection is successful, an "open" `ConnectionEvent` is delivered to any `ConnectionListeners` on this service.

      Most clients should just call this method to connect to the service.

      It is an error to connect to an already connected service.

      The implementation provided here simply calls the following `connect(String, String, String)` method with nulls.

      Throws:
        `AuthenticationFailedException` - for authentication failures
        `MessagingException` - for other failures
        `java.lang.IllegalStateException` - if the service is already connected
      See Also:
        `ConnectionEvent`

    - #### connect

          public void connect(java.lang.String host,
                              java.lang.String user,
                              java.lang.String password)
                       throws MessagingException

      Connect to the specified address. This method provides a simple authentication scheme that requires a username and password.

      If the connection is successful, an "open" `ConnectionEvent` is delivered to any `ConnectionListeners` on this service.

      It is an error to connect to an already connected service.

      The implementation in the Service class will collect defaults for the host, user, and password from the session, from the `URLName` for this service, and from the supplied parameters and then call the `protocolConnect` method. If the `protocolConnect` method returns `false`, the user will be prompted for any missing information and the `protocolConnect` method will be called again. The subclass should override the `protocolConnect` method. The subclass should also implement the `getURLName` method, or use the implementation in this class.

      On a successful connection, the `setURLName` method is called with a URLName that includes the information used to make the connection, including the password.

      If the username passed in is null, a default value will be chosen as described above. If the password passed in is null and this is the first successful connection to this service, the user name and the password collected from the user will be saved as defaults for subsequent connection attempts to this same service when using other Service object instances (the connection information is typically always saved within a particular Service object instance). The password is saved using the Session method `setPasswordAuthentication`. If the password passed in is not null, it is not saved, on the assumption that the application is managing passwords explicitly.

      Parameters:
        `host` - the host to connect to
        `user` - the user name
        `password` - this user's password
      Throws:
        `AuthenticationFailedException` - for authentication failures
        `MessagingException` - for other failures
        `java.lang.IllegalStateException` - if the service is already connected
      See Also:
        `ConnectionEvent`, `Session.setPasswordAuthentication(javax.mail.URLName, javax.mail.PasswordAuthentication)`

    - #### connect

          public void connect(java.lang.String user,
                              java.lang.String password)
                       throws MessagingException

      Connect to the current host using the specified username and password. This method is equivalent to calling the `connect(host, user, password)` method with null for the host name.
      Parameters:
        `user` - the user name
        `password` - this user's password
      Throws:
        `AuthenticationFailedException` - for authentication failures
        `MessagingException` - for other failures
        `java.lang.IllegalStateException` - if the service is already connected
      Since:
        JavaMail 1.4
      See Also:
        `ConnectionEvent`, `Session.setPasswordAuthentication(javax.mail.URLName, javax.mail.PasswordAuthentication)`, `connect(java.lang.String, java.lang.String, java.lang.String)`

    - #### connect

          public void connect(java.lang.String host,
                              int port,
                              java.lang.String user,
                              java.lang.String password)
                       throws MessagingException

      Similar to connect(host, user, password) except a specific port can be specified.
      Parameters:
        `host` - the host to connect to
        `port` - the port to connect to (-1 means the default port)
        `user` - the user name
        `password` - this user's password
      Throws:
        `AuthenticationFailedException` - for authentication failures
        `MessagingException` - for other failures
        `java.lang.IllegalStateException` - if the service is already connected
      See Also:
        `connect(java.lang.String, java.lang.String, java.lang.String)`, `ConnectionEvent`

    - #### protocolConnect

          protected boolean protocolConnect(java.lang.String host,
                                            int port,
                                            java.lang.String user,
                                            java.lang.String password)
                                     throws MessagingException

      The service implementation should override this method to perform the actual protocol-specific connection attempt. The default implementation of the `connect` method calls this method as needed.

      The `protocolConnect` method should return `false` if a user name or password is required for authentication but the corresponding parameter is null; the `connect` method will prompt the user when needed to supply missing information. This method may also return `false` if authentication fails for the supplied user name or password. Alternatively, this method may throw an AuthenticationFailedException when authentication fails. This exception may include a String message with more detail about the failure.

      The `protocolConnect` method should throw an exception to report failures not related to authentication, such as an invalid host name or port number, loss of a connection during the authentication process, unavailability of the server, etc.

      Parameters:
        `host` - the name of the host to connect to
        `port` - the port to use (-1 means use default port)
        `user` - the name of the user to login as
        `password` - the user's password
      Returns:
        true if connection successful, false if authentication failed
      Throws:
        `AuthenticationFailedException` - for authentication failures
        `MessagingException` - for non-authentication failures

    - #### isConnected

          public boolean isConnected()

      Is this service currently connected?

      This implementation uses a private boolean field to store the connection state. This method returns the value of that field.

      Subclasses may want to override this method to verify that any connection to the message store is still alive.

      Returns:
        true if the service is connected, false if it is not connected

    - #### setConnected

          protected void setConnected(boolean connected)

      Set the connection state of this service. The connection state will automatically be set by the service implementation during the `connect` and `close` methods. Subclasses will need to call this method to set the state if the service was automatically disconnected.

      The implementation in this class merely sets the private field returned by the `isConnected` method.

      Parameters:
        `connected` - true if the service is connected, false if it is not connected

    - #### close

          public void close()
                     throws MessagingException

      Close this service and terminate its connection. A close ConnectionEvent is delivered to any ConnectionListeners. Any Messaging components (Folders, Messages, etc.) belonging to this service are invalid after this service is closed. Note that the service is closed even if this method terminates abnormally by throwing a MessagingException.

      This implementation uses `setConnected(false)` to set this service's connected state to `false`. It will then send a close ConnectionEvent to any registered ConnectionListeners. Subclasses overriding this method to do implementation specific cleanup should call this method as a last step to insure event notification, probably by including a call to `super.close()` in a `finally` clause.

      Throws:
        `MessagingException` - for errors while closing
      See Also:
        `ConnectionEvent`

    - #### getURLName

          public URLName getURLName()

      Return a URLName representing this service. The returned URLName does not include the password field.

      Subclasses should only override this method if their URLName does not follow the standard format.

      The implementation in the Service class returns (usually a copy of) the `url` field with the password and file information stripped out.

      Returns:
        the URLName representing this service
      See Also:
        `URLName`

    - #### setURLName

          protected void setURLName(URLName url)

      Set the URLName representing this service. Normally used to update the `url` field after a service has successfully connected.

      Subclasses should only override this method if their URL does not follow the standard format. In particular, subclasses should override this method if their URL does not require all the possible fields supported by `URLName`; a new `URLName` should be constructed with any unneeded fields removed.

      The implementation in the Service class simply sets the `url` field.

      See Also:
        `URLName`

    - #### addConnectionListener

          public void addConnectionListener(ConnectionListener l)

      Add a listener for Connection events on this service.

      The default implementation provided here adds this listener to an internal list of ConnectionListeners.

      Parameters:
        `l` - the Listener for Connection events
      See Also:
        `ConnectionEvent`

    - #### removeConnectionListener

          public void removeConnectionListener(ConnectionListener l)

      Remove a Connection event listener.

      The default implementation provided here removes this listener from the internal list of ConnectionListeners.

      Parameters:
        `l` - the listener
      See Also:
        `addConnectionListener(javax.mail.event.ConnectionListener)`

    - #### notifyConnectionListeners

          protected void notifyConnectionListeners(int type)

      Notify all ConnectionListeners. Service implementations are expected to use this method to broadcast connection events.

      The provided default implementation queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the registered ConnectionListeners. Note that the event dispatching occurs in a separate thread, thus avoiding potential deadlock problems.

    - #### toString

          public java.lang.String toString()

      Return `getURLName.toString()` if this service has a URLName, otherwise it will return the default `toString`.
      Overrides:
        `toString` in class `java.lang.Object`

    - #### queueEvent

          protected void queueEvent(MailEvent event,
                                    java.util.Vector vector)

      Add the event and vector of listeners to the queue to be delivered.

    - #### finalize

          protected void finalize()
                           throws java.lang.Throwable

      Stop the event dispatcher thread so the queue can be garbage collected.
      Overrides:
        `finalize` in class `java.lang.Object`
      Throws:
        `java.lang.Throwable`

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