# Interface JMXConnector

All Superinterfaces:
  `AutoCloseable, Closeable`

All Known Implementing Classes:
  `RMIConnector`

public interface JMXConnector extends Closeable

The client end of a JMX API connector. An object of this type can be used to establish a connection to a connector server.

A newly-created object of this type is unconnected. Its `connect` method must be called before it can be used. However, objects created by `JMXConnectorFactory.connect` are already connected.

Since:
  1.5

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `CREDENTIALS`
  Name of the attribute that specifies the credentials to send to the connector server during connection.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addConnectionNotificationListener(NotificationListener listener, NotificationFilter filter, Object handback)`
  Adds a listener to be informed of changes in connection status.
  `void`
  `close()`
  Closes the client connection to its server.
  `void`
  `connect()`
  Establishes the connection to the connector server.
  `void`
  `connect(Map<String,?> env)`
  Establishes the connection to the connector server.
  `String`
  `getConnectionId()`
  Gets this connection's ID from the connector server.
  `MBeanServerConnection`
  `getMBeanServerConnection()`
  Returns an `MBeanServerConnection` object representing a remote MBean server.
  `default MBeanServerConnection`
  `getMBeanServerConnection(Subject delegationSubject)`
  Deprecated, for removal: This API element is subject to removal in a future version.
  This method supported the legacy Subject Delegation feature, which has been removed.
  `void`
  `removeConnectionNotificationListener(NotificationListener listener)`
  Removes a listener from the list to be informed of changes in status.
  `void`
  `removeConnectionNotificationListener(NotificationListener l, NotificationFilter f, Object handback)`
  Removes a listener from the list to be informed of changes in status.

- ## Field Details

  - ### CREDENTIALS

    static final String CREDENTIALS

    Name of the attribute that specifies the credentials to send to the connector server during connection. The value associated with this attribute, if any, is a serializable object of an appropriate type for the server's `JMXAuthenticator`.

    See Also:
      - Constant Field Values

- ## Method Details

  - ### connect

    void connect() throws IOException

    Establishes the connection to the connector server. This method is equivalent to `connect(null)`.

    Throws:
      `IOException` - if the connection could not be made because of a communication problem.
      `SecurityException` - if the connection could not be made for security reasons.

  - ### connect

    void connect(Map<String,?> env) throws IOException

    Establishes the connection to the connector server.

    If `connect` has already been called successfully on this object, calling it again has no effect. If, however, `close()` was called after `connect`, the new `connect` will throw an `IOException`.

    Otherwise, either `connect` has never been called on this object, or it has been called but produced an exception. Then calling `connect` will attempt to establish a connection to the connector server.

    Parameters:
      `env` - the properties of the connection. Properties in this map override properties in the map specified when the `JMXConnector` was created, if any. This parameter can be null, which is equivalent to an empty map.
    Throws:
      `IOException` - if the connection could not be made because of a communication problem.
      `SecurityException` - if the connection could not be made for security reasons.

  - ### getMBeanServerConnection

    MBeanServerConnection getMBeanServerConnection() throws IOException

    Returns an `MBeanServerConnection` object representing a remote MBean server. For a given `JMXConnector`, two successful calls to this method will usually return the same `MBeanServerConnection` object, though this is not required.

    For each method in the returned `MBeanServerConnection`, calling the method causes the corresponding method to be called in the remote MBean server. The value returned by the MBean server method is the value returned to the client. If the MBean server method produces an `Exception`, the same `Exception` is seen by the client. If the MBean server method, or the attempt to call it, produces an `Error`, the `Error` is wrapped in a `JMXServerErrorException`, which is seen by the client.

    Returns:
      an object that implements the `MBeanServerConnection` interface by forwarding its methods to the remote MBean server.
    Throws:
      `IOException` - if a valid `MBeanServerConnection` cannot be created, for instance because the connection to the remote MBean server has not yet been established (with the `connect` method), or it has been closed, or it has broken.

  - ### getMBeanServerConnection

    @Deprecated(since="21", forRemoval=true) default MBeanServerConnection getMBeanServerConnection(Subject delegationSubject) throws IOException
    Deprecated, for removal: This API element is subject to removal in a future version.
    This method supported the legacy Subject Delegation feature, which has been removed. There is no replacement.

    When `delegationSubject` is `null`, calling his method is equivalent to calling `getMBeanServerConnection()`.

    Implementation Requirements:
      The default implementation of this method throws `UnsupportedOperationException` if `delegationSubject` is non-null. Otherwise it calls `getMBeanServerConnection()`.
    Parameters:
      `delegationSubject` - must be `null`.
    Returns:
      an object that implements the `MBeanServerConnection` interface by forwarding its methods to the remote MBean server.
    Throws:
      `IOException` - if a valid `MBeanServerConnection` cannot be created, for instance because the connection to the remote MBean server has not yet been established (with the `connect` method), or it has been closed, or it has broken.
      `UnsupportedOperationException` - if `delegationSubject` is non-null.

  - ### close

    void close() throws IOException

    Closes the client connection to its server. Any ongoing or new request using the MBeanServerConnection returned by `getMBeanServerConnection()` will get an `IOException`.

    If `close` has already been called successfully on this object, calling it again has no effect. If `close` has never been called, or if it was called but produced an exception, an attempt will be made to close the connection. This attempt can succeed, in which case `close` will return normally, or it can generate an exception.

    Closing a connection is a potentially slow operation. For example, if the server has crashed, the close operation might have to wait for a network protocol timeout. Callers that do not want to block in a close operation should do it in a separate thread.

    Specified by:
      `close` in interface `AutoCloseable`
    Specified by:
      `close` in interface `Closeable`
    Throws:
      `IOException` - if the connection cannot be closed cleanly. If this exception is thrown, it is not known whether the server end of the connection has been cleanly closed.

  - ### addConnectionNotificationListener

    void addConnectionNotificationListener(NotificationListener listener, NotificationFilter filter, Object handback)

    Adds a listener to be informed of changes in connection status. The listener will receive notifications of type `JMXConnectionNotification`. An implementation can send other types of notifications too.

    Any number of listeners can be added with this method. The same listener can be added more than once with the same or different values for the filter and handback. There is no special treatment of a duplicate entry. For example, if a listener is registered twice with no filter, then its `handleNotification` method will be called twice for each notification.

    Parameters:
      `listener` - a listener to receive connection status notifications.
      `filter` - a filter to select which notifications are to be delivered to the listener, or null if all notifications are to be delivered.
      `handback` - an object to be given to the listener along with each notification. Can be null.
    Throws:
      `NullPointerException` - if `listener` is null.
    See Also:
      - `removeConnectionNotificationListener(NotificationListener)`
      - `NotificationBroadcaster.addNotificationListener(NotificationListener, NotificationFilter, Object)`

  - ### removeConnectionNotificationListener

    void removeConnectionNotificationListener(NotificationListener listener) throws ListenerNotFoundException

    Removes a listener from the list to be informed of changes in status. The listener must previously have been added. If there is more than one matching listener, all are removed.

    Parameters:
      `listener` - a listener to receive connection status notifications.
    Throws:
      `NullPointerException` - if `listener` is null.
      `ListenerNotFoundException` - if the listener is not registered with this `JMXConnector`.
    See Also:
      - `removeConnectionNotificationListener(NotificationListener, NotificationFilter, Object)`
      - `addConnectionNotificationListener(NotificationListener, NotificationFilter, Object)`
      - `NotificationEmitter.removeNotificationListener(NotificationListener, NotificationFilter, Object)`

  - ### removeConnectionNotificationListener

    void removeConnectionNotificationListener(NotificationListener l, NotificationFilter f, Object handback) throws ListenerNotFoundException

    Removes a listener from the list to be informed of changes in status. The listener must previously have been added with the same three parameters. If there is more than one matching listener, only one is removed.

    Parameters:
      `l` - a listener to receive connection status notifications.
      `f` - a filter to select which notifications are to be delivered to the listener. Can be null.
      `handback` - an object to be given to the listener along with each notification. Can be null.
    Throws:
      `ListenerNotFoundException` - if the listener is not registered with this `JMXConnector`, or is not registered with the given filter and handback.
    See Also:
      - `removeConnectionNotificationListener(NotificationListener)`
      - `addConnectionNotificationListener(NotificationListener, NotificationFilter, Object)`
      - `NotificationEmitter.removeNotificationListener(NotificationListener, NotificationFilter, Object)`

  - ### getConnectionId

    String getConnectionId() throws IOException

    Gets this connection's ID from the connector server. For a given connector server, every connection will have a unique id which does not change during the lifetime of the connection.

    Returns:
      the unique ID of this connection. This is the same as the ID that the connector server includes in its `JMXConnectionNotification`s. The `package description` describes the conventions for connection IDs.
    Throws:
      `IOException` - if the connection ID cannot be obtained, for instance because the connection is closed or broken.