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## org.jgroups.blocks
Class MessageListenerAdapter

    java.lang.Object
      org.jgroups.blocks.MessageListenerAdapter

All Implemented Interfaces:
  ExtendedMessageListener, MessageListener

    public class MessageListenerAdapter

extends java.lang.Object
implements ExtendedMessageListener

This class provides multiplexing possibilities for `MessageListener` instances. Usually, we have more than one instance willing to listen to incoming messages, but only one that can produce state for group. `PullPushAdapter` allows only one instance of `MessageListener` to be registered for message notification. With help of this class you can overcome this limitation.

Author:
  Roman Rokytskyy (rrokytskyy@acm.org)

Field Summary
`protected java.util.HashSet` | `messageListeners`
`protected MessageListener[]` | `messageListenersCache`
`protected MessageListener` | `stateListener`

Constructor Summary
`MessageListenerAdapter()` Create default instance of this class.
`MessageListenerAdapter(MessageListener mainListener)` Create instance of this class.

Method Summary
`void` | `addMessageListener(MessageListener listener)` Add message listener to this adapter.
`byte[]` | `getState()` Get state from state listener if present.
`void` | `getState(java.io.OutputStream ostream)` Allows an application to write a state through a provided OutputStream.
`byte[]` | `getState(java.lang.String state_id)` Allows an application to provide a partial state as a byte array
`void` | `getState(java.lang.String state_id, java.io.OutputStream ostream)` Allows an application to write a partial state through a provided OutputStream.
`void` | `receive(Message msg)` Receive message from group.
`void` | `removeMessageListener(MessageListener listener)` Remove message listener from this adapter.
`void` | `setState(byte[] state)` Set state of ths group.
`void` | `setState(java.io.InputStream istream)` Allows an application to read a state through a provided InputStream.
`void` | `setState(java.lang.String state_id, byte[] state)` Allows an application to read a partial state indicated by state_id from a given state byte array parameter.
`void` | `setState(java.lang.String state_id, java.io.InputStream istream)` Allows an application to read a partial state through a provided InputStream.
`void` | `setStateListener(MessageListener listener)` Register `listener` for state notification events.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### stateListener

    protected MessageListener stateListener

### messageListeners

    protected final java.util.HashSet messageListeners

### messageListenersCache

    protected MessageListener[] messageListenersCache

Constructor Detail

### MessageListenerAdapter

    public MessageListenerAdapter()

  Create default instance of this class. Newly created instance will have no message or state listeners. You have to use `addMessageListener(MessageListener)` or `removeMessageListener(MessageListener)` to add or remove message listeners, and `setStateListener(MessageListener)` to set listener that will participate in state transfer.

### MessageListenerAdapter

    public MessageListenerAdapter(MessageListener mainListener)

  Create instance of this class. `mainListener` is a main listener instance that received message notifications and can get and set group state.

  Parameters:
    `mainListener` - instance of `MessageListener` that will provide state messages.

Method Detail

### getState

    public byte[] getState()

  Get state from state listener if present.

  Specified by:
    `getState` in interface `MessageListener`
  Returns:
    current state of the group state or `null` if no state listeners were registered.

### getState

    public byte[] getState(java.lang.String state_id)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to provide a partial state as a byte array

  Specified by:
    `getState` in interface `ExtendedMessageListener`
  Parameters:
    `state_id` - id of the partial state requested
  Returns:
    partial state for the given state_id

### getState

    public void getState(java.io.OutputStream ostream)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to write a state through a provided OutputStream. An application is obligated to always close the given OutputStream reference.

  Specified by:
    `getState` in interface `ExtendedMessageListener`
  Parameters:
    `ostream` - the OutputStream
  See Also:
    `OutputStream.close()`

### getState

    public void getState(java.lang.String state_id,
                         java.io.OutputStream ostream)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to write a partial state through a provided OutputStream. An application is obligated to always close the given OutputStream reference.

  Specified by:
    `getState` in interface `ExtendedMessageListener`
  Parameters:
    `state_id` - id of the partial state requested
    `ostream` - the OutputStream
  See Also:
    `OutputStream.close()`

### receive

    public void receive(Message msg)

  Receive message from group. This method will send this message to each message listener that was registered in this adapter.

  Specified by:
    `receive` in interface `MessageListener`
  Parameters:
    `msg` - message to distribute within message listeners.

### setState

    public void setState(byte[] state)

  Set state of ths group. This method will delegate call to state listener if it was previously registered.

  Specified by:
    `setState` in interface `MessageListener`

### setState

    public void setState(java.lang.String state_id,
                         byte[] state)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to read a partial state indicated by state_id from a given state byte array parameter.

  Specified by:
    `setState` in interface `ExtendedMessageListener`
  Parameters:
    `state_id` - id of the partial state requested
    `state` - partial state for the given state_id

### setState

    public void setState(java.io.InputStream istream)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to read a state through a provided InputStream. An application is obligated to always close the given InputStream reference.

  Specified by:
    `setState` in interface `ExtendedMessageListener`
  Parameters:
    `istream` - the InputStream
  See Also:
    `InputStream.close()`

### setState

    public void setState(java.lang.String state_id,
                         java.io.InputStream istream)

  Description copied from interface: `ExtendedMessageListener`
  Allows an application to read a partial state through a provided InputStream. An application is obligated to always close the given InputStream reference.

  Specified by:
    `setState` in interface `ExtendedMessageListener`
  Parameters:
    `state_id` - id of the partial state requested
    `istream` - the InputStream
  See Also:
    `InputStream.close()`

### addMessageListener

    public final void addMessageListener(MessageListener listener)

  Add message listener to this adapter. This method registers `listener` for message notification.

  Note, state notification will not be used.

### removeMessageListener

    public void removeMessageListener(MessageListener listener)

  Remove message listener from this adapter. This method deregisters `listener` from message notification.

### setStateListener

    public void setStateListener(MessageListener listener)

  Register `listener` for state notification events. There can be only one state listener per adapter.

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Copyright © 1998-2009 Bela Ban / Red Hat. All Rights Reserved.