Package org.jgroups

Interface Message

All Superinterfaces:
Constructable<Message>, SizeStreamable, Streamable
All Known Implementing Classes:
BaseMessage, BatchMessage, BytesMessage, CompositeMessage, EmptyMessage, FragmentedMessage, LongMessage, NioMessage, ObjectMessage
public interface Message extends SizeStreamable, Constructable<Message>
A Message is used to send data to members of a group. It contains the address of the sender, the destination address, (typically) a payload, flags and a list of headers.

Subclasses define different types of payloads, e.g. byte arrays, ByteBuffers, Objects etc.

Since:
5.0

  • Field Details

  • Method Details

    • getType

      short getType()
      Returns the type of the message, e.g. BYTES_MSG, OBJ_MSG etc

    • getDest

      Address getDest()
      Returns the destination address to send the message to. A null value sends the message to all cluster members

    • dest

      default Address dest()

    • setDest

      Message setDest(Address new_dest)
      Sets the destination address to send the message to. A null value sends the message to all cluster members

    • dest

      default Message dest(Address new_dest)

    • getSrc

      Address getSrc()
      Returns the address of the sender

    • src

      default Address src()

    • setSrc

      Message setSrc(Address new_src)
      Sets the address of the sender of this message

    • src

      default Message src(Address new_src)

    • putHeader

      Message putHeader(short id, Header hdr)
      Adds a header to the message

    • putHeaderIfAbsent

      Message putHeaderIfAbsent(short id, Header hdr)
      Adds a header to a message if not present

    • getHeader

      <T extends Header> T getHeader(short id)
      Gets a header from the message

    • getHeaders

      Map<Short,Header> getHeaders()
      Returns a hashmap of all header IDs and their associated headers

    • getNumHeaders

      int getNumHeaders()
      Returns the number of headers

    • printHeaders

      String printHeaders()
      Returns a pretty-printed string of the headers

    • clearHeaders

      Message clearHeaders()
      Removes all headers: use carefully!

    • setFlag

      Message setFlag(Message.Flag... flags)
      Sets one or more flags (xor-ing existing flags)

    • setFlag

      default Message setFlag(short flag, boolean transient_flags)
      Sets the flags as a short; this way, multiple flags can be set in one operation
      Parameters:
      flag - The flag to be set (as a short). Overrides existing flags (no xor-ing)
      transient_flags - True if the flag is transient, false otherwise

    • setFlag

      Message setFlag(short flag, boolean transient_flags, boolean xor)
      Sets the flags as a short; this way, multiple flags can be set in one operation
      Parameters:
      flag - The flag to be set (as a short). Overrides existing flags (no xor-ing)
      transient_flags - True if the flag is transient, false otherwise
      xor - When true, existing flags will be xor-ed with flag, otherwise not

    • setFlag

      Message setFlag(Message.TransientFlag... flags)
      Sets one or more transient flags (xor-ing). Transient flags are not marshalled

    • setFlagIfAbsent

      boolean setFlagIfAbsent(Message.TransientFlag flag)
      Atomically sets a transient flag if not set. Returns true if the flags was set, else false (already set)

    • getFlags

      short getFlags(boolean transient_flags)
      Returns the flags as an or-ed short
      Parameters:
      transient_flags - Returns transient flags if true, else regular flags

    • getFlags

      default short getFlags()

    • clearFlag

      Message clearFlag(Message.Flag... flags)
      Removes a number of flags from the message. No-op for a flag if it is not set

    • clearFlag

      Message clearFlag(Message.TransientFlag... flags)
      Removes a number of transient flags from the message. No-op for a flag if it is not set

    • isFlagSet

      boolean isFlagSet(Message.Flag flag)
      Returns true if a flag is set, false otherwise

    • isFlagSet

      boolean isFlagSet(Message.TransientFlag flag)
      Returns true if a transient flag is set, false otherwise

    • copy

      Message copy(boolean copy_payload, boolean copy_headers)
      Copies a message
      Parameters:
      copy_payload - If true, the payload is copied, else it is null in the copied message
      copy_headers - If true, the headers are copied

    • hasPayload

      boolean hasPayload()
      Returns true if the message has a payload, e.g. a byte[] array in a BytesMessage or an object in an ObjectMessage. This is more generic than hasArray(), as it is not just applicable to a byte array.
      Returns:
      True if the message has a payload

    • hasArray

      boolean hasArray()
      Returns true if this message has a byte[] array as payload (even if it's null!), false otherwise

    • getArray

      byte[] getArray()
      Returns a reference to the payload (byte array). Note that this array should not be modified as we do not copy the array on copy() or clone(): the array of the copied message is simply a reference to the old array.

      Even if offset and length are used: we return the entire array, not a subset.

      Throws an exception if the message does not have a byte[] array payload (hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage. It is recommended to downcast a Message to the correct subtype and use the methods available there to get/set the payload.

    • getOffset

      int getOffset()
      Returns the offset of the byte[] array at which user data starts. Throws an exception if the message does not have a byte[] array payload (if hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage.

    • getLength

      int getLength()
      Returns the length of the byte[] array payload. If the message does not have a byte[] array payload (hasArray() is false), then the serialized size may be returned, or an implementation may choose to throw an exception

    • setArray

      Message setArray(byte[] b, int offset, int length)
      Sets the byte array in a message.

      Throws an exception if the message does not have a byte[] array payload (hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage. It is recommended to downcast a Message to the correct subtype and use the methods available there to get/set the payload.

    • setArray

      default Message setArray(byte[] b)

    • setArray

      Message setArray(ByteArray buf)
      Sets the byte array in a message.

      Throws an exception if the message does not have a byte[] array payload (hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage. It is recommended to downcast a Message to the correct subtype and use the methods available there to get/set the payload.

    • getObject

      <T> T getObject()
      Gets an object from the payload. If the payload is a byte[] array (e.g. as in BytesMessage), an attempt to de-serialize the array into an object is made, and the object returned.

      If the payload is an object (e.g. as is the case in ObjectMessage), the object will be returned directly.

    • setObject

      Message setObject(Object obj)
      Sets an object in a message. In a ObjectMessage, the object is set directly. In a BytesMessage, the object is serialized into a byte[] array and then the array is set as the payload of the message

    • getPayload

      <T> T getPayload()
      Returns the payload without any conversion (e.g. as in getObject() or getArray())
      Type Parameters:
      T - The type of the object
      Returns:
      The payload

    • setPayload

      Message setPayload(Object pl)
      Sets the payload
      Parameters:
      pl - The paylolad

    • size

      int size()
      Returns the exact size of the marshalled message
      Returns:
      The number of bytes for the marshalled message

    • writeToNoAddrs

      void writeToNoAddrs(Address src, DataOutput out) throws IOException
      Writes the message to an output stream excluding the destination (and possibly source) address
      Throws:
      IOException

    • writePayload

      void writePayload(DataOutput out) throws IOException
      Throws:
      IOException

    • readPayload

      void readPayload(DataInput in) throws IOException, ClassNotFoundException
      Throws:
      IOException
      ClassNotFoundException