ChannelInterceptor (Apache Tomcat 8.5.57 API Documentation)

org.apache.catalina.tribes

## Interface ChannelInterceptor

- All Superinterfaces:
    Heartbeat, MembershipListener
  All Known Implementing Classes:
    ChannelCoordinator, ChannelInterceptorBase, DomainFilterInterceptor, EncryptInterceptor, FragmentationInterceptor, GroupChannel, GzipInterceptor, MessageDispatchInterceptor, NonBlockingCoordinator, OrderInterceptor, SimpleCoordinator, StaticMembershipInterceptor, TcpFailureDetector, TcpPingInterceptor, ThroughputInterceptor, TwoPhaseCommitInterceptor

      public interface ChannelInterceptor
      extends MembershipListener, Heartbeat

  A ChannelInterceptor is an interceptor that intercepts messages and membership messages in the channel stack. This allows interceptors to modify the message or perform other actions when a message is sent or received.
  Interceptors are tied together in a linked list.
  See Also:
    `ChannelInterceptorBase`

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Interface and Description
    --- | ---
    `static interface` | `ChannelInterceptor.InterceptorEvent`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `fireInterceptorEvent(ChannelInterceptor.InterceptorEvent event)`
    `Channel` | `getChannel()` Return the channel that is related to this interceptor
    `Member` | `getLocalMember(boolean incAliveTime)` Intercepts the `Channel.getLocalMember(boolean)` method
    `Member` | `getMember(Member mbr)` Intercepts the `Channel.getMember(Member)` method
    `Member[]` | `getMembers()` Intercepts the `Channel.getMembers()` method
    `ChannelInterceptor` | `getNext()` Retrieve the next interceptor in the list
    `int` | `getOptionFlag()` An interceptor can react to a message based on a set bit on the message options.
    `ChannelInterceptor` | `getPrevious()` Retrieve the previous interceptor in the list
    `boolean` | `hasMembers()` Intercepts the `Channel.hasMembers()` method
    `void` | `heartbeat()` The `heartbeat()` method gets invoked periodically to allow interceptors to clean up resources, time out object and perform actions that are unrelated to sending/receiving data.
    `void` | `messageReceived(ChannelMessage data)` the `messageReceived` is invoked when a message is received.
    `void` | `sendMessage(Member[] destination, ChannelMessage msg, InterceptorPayload payload)` The `sendMessage` method is called when a message is being sent to one more destinations.
    `void` | `setChannel(Channel channel)` Set the channel that is related to this interceptor
    `void` | `setNext(ChannelInterceptor next)` Set the next interceptor in the list of interceptors
    `void` | `setOptionFlag(int flag)` Sets the option flag
    `void` | `setPrevious(ChannelInterceptor previous)` Set the previous interceptor in the list
    `void` | `start(int svc)` Starts up the channel.
    `void` | `stop(int svc)` Shuts down the channel.

    - ### Methods inherited from interface org.apache.catalina.tribes.MembershipListener

      `memberAdded, memberDisappeared`

- - ### Method Detail

    - #### getOptionFlag

          int getOptionFlag()

      An interceptor can react to a message based on a set bit on the message options.
      When a message is sent, the options can be retrieved from ChannelMessage.getOptions() and if the bit is set, this interceptor will react to it.
      A simple evaluation if an interceptor should react to the message would be:
      `boolean react = (getOptionFlag() == (getOptionFlag() & ChannelMessage.getOptions()));`
      The default option is 0, meaning there is no way for the application to trigger the interceptor. The interceptor itself will decide.
      Returns:
        int
      See Also:
        `ChannelMessage.getOptions()`

    - #### setOptionFlag

          void setOptionFlag(int flag)

      Sets the option flag
      Parameters:
        `flag` - int
      See Also:
        `getOptionFlag()`

    - #### setNext

          void setNext(ChannelInterceptor next)

      Set the next interceptor in the list of interceptors
      Parameters:
        `next` - ChannelInterceptor

    - #### getNext

          ChannelInterceptor getNext()

      Retrieve the next interceptor in the list
      Returns:
        ChannelInterceptor - returns the next interceptor in the list or null if no more interceptors exist

    - #### setPrevious

          void setPrevious(ChannelInterceptor previous)

      Set the previous interceptor in the list
      Parameters:
        `previous` - ChannelInterceptor

    - #### getPrevious

          ChannelInterceptor getPrevious()

      Retrieve the previous interceptor in the list
      Returns:
        ChannelInterceptor - returns the previous interceptor in the list or null if no more interceptors exist

    - #### sendMessage

          void sendMessage(Member[] destination,
                         ChannelMessage msg,
                         InterceptorPayload payload)
                           throws ChannelException

      The `sendMessage` method is called when a message is being sent to one more destinations. The interceptor can modify any of the parameters and then pass on the message down the stack by invoking `getNext().sendMessage(destination,msg,payload)`
      Alternatively the interceptor can stop the message from being sent by not invoking `getNext().sendMessage(destination,msg,payload)`
      If the message is to be sent asynchronous the application can be notified of completion and errors by passing in an error handler attached to a payload object.
      The ChannelMessage.getAddress contains Channel.getLocalMember, and can be overwritten to simulate a message sent from another node.
      Parameters:
        `destination` - Member[] - the destination for this message
        `msg` - ChannelMessage - the message to be sent
        `payload` - InterceptorPayload - the payload, carrying an error handler and future useful data, can be null
      Throws:
        `ChannelException` - if a serialization error happens.
      See Also:
        `ErrorHandler`, `InterceptorPayload`

    - #### messageReceived

          void messageReceived(ChannelMessage data)

      the `messageReceived` is invoked when a message is received. `ChannelMessage.getAddress()` is the sender, or the reply-to address if it has been overwritten.
      Parameters:
        `data` - ChannelMessage

    - #### heartbeat

          void heartbeat()

      The `heartbeat()` method gets invoked periodically to allow interceptors to clean up resources, time out object and perform actions that are unrelated to sending/receiving data.
      Specified by:
        `heartbeat` in interface `Heartbeat`

    - #### hasMembers

          boolean hasMembers()

      Intercepts the `Channel.hasMembers()` method
      Returns:
        boolean - if the channel has members in its membership group
      See Also:
        `Channel.hasMembers()`

    - #### getMembers

          Member[] getMembers()

      Intercepts the `Channel.getMembers()` method
      Returns:
        Member[]
      See Also:
        `Channel.getMembers()`

    - #### getLocalMember

          Member getLocalMember(boolean incAliveTime)

      Intercepts the `Channel.getLocalMember(boolean)` method
      Parameters:
        `incAliveTime` - boolean
      Returns:
        Member
      See Also:
        `Channel.getLocalMember(boolean)`

    - #### getMember

          Member getMember(Member mbr)

      Intercepts the `Channel.getMember(Member)` method
      Parameters:
        `mbr` - Member
      Returns:
        Member - the actual member information, including stay alive
      See Also:
        `Channel.getMember(Member)`

    - #### start

          void start(int svc)
                     throws ChannelException

      Starts up the channel. This can be called multiple times for individual services to start The svc parameter can be the logical or value of any constants
      Parameters:
        `svc` - int value of
        Channel.DEFAULT - will start all services
        Channel.MBR_RX_SEQ - starts the membership receiver
        Channel.MBR_TX_SEQ - starts the membership broadcaster
        Channel.SND_TX_SEQ - starts the replication transmitter
        Channel.SND_RX_SEQ - starts the replication receiver
      Throws:
        `ChannelException` - if a startup error occurs or the service is already started.
      See Also:
        `Channel`

    - #### stop

          void stop(int svc)
                    throws ChannelException

      Shuts down the channel. This can be called multiple times for individual services to shutdown The svc parameter can be the logical or value of any constants
      Parameters:
        `svc` - int value of
        Channel.DEFAULT - will shutdown all services
        Channel.MBR_RX_SEQ - stops the membership receiver
        Channel.MBR_TX_SEQ - stops the membership broadcaster
        Channel.SND_TX_SEQ - stops the replication transmitter
        Channel.SND_RX_SEQ - stops the replication receiver
      Throws:
        `ChannelException` - if a startup error occurs or the service is already started.
      See Also:
        `Channel`

    - #### fireInterceptorEvent

          void fireInterceptorEvent(ChannelInterceptor.InterceptorEvent event)

    - #### getChannel

          Channel getChannel()

      Return the channel that is related to this interceptor
      Returns:
        Channel

    - #### setChannel

          void setChannel(Channel channel)

      Set the channel that is related to this interceptor
      Parameters:
        `channel` - The channel

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