Package org.jgroups

Class EmptyMessage

java.lang.Object
org.jgroups.BaseMessage
org.jgroups.EmptyMessage
All Implemented Interfaces:
Constructable<Message>, Message, SizeStreamable, Streamable
public class EmptyMessage extends BaseMessage
A Message without a payload; optimized for sending only headers (e.g. heartbeats in failure detection)
Since:
5.0

  • Constructor Details

    • EmptyMessage

      public EmptyMessage()

    • EmptyMessage

      public EmptyMessage(Address dest)

  • Method Details

    • getType

      public short getType()
      Description copied from interface: Message
      Returns the type of the message, e.g. BYTES_MSG, OBJ_MSG etc

    • create

      public Supplier<Message> create()
      Description copied from interface: Constructable
      Creates an instance of the class implementing this interface

    • hasPayload

      public boolean hasPayload()
      Description copied from interface: Message
      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 Message.hasArray(), as it is not just applicable to a byte array.
      Returns:
      True if the message has a payload

    • hasArray

      public boolean hasArray()
      Description copied from interface: Message
      Returns true if this message has a byte[] array as payload (even if it's null!), false otherwise

    • getArray

      public byte[] getArray()
      Description copied from interface: Message
      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 (Message.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

      public int getOffset()
      Description copied from interface: Message
      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 Message.hasArray() is false).

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

    • getLength

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

    • setArray

      public EmptyMessage setArray(byte[] b, int off, int len)
      Description copied from interface: Message
      Sets the byte array in a message.

      Throws an exception if the message does not have a byte[] array payload (Message.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

      public EmptyMessage setArray(ByteArray buf)
      Description copied from interface: Message
      Sets the byte array in a message.

      Throws an exception if the message does not have a byte[] array payload (Message.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

      public <T> T getObject()
      Description copied from interface: Message
      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

      public EmptyMessage setObject(Object obj)
      Description copied from interface: Message
      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

    • writePayload

      public void writePayload(DataOutput out) throws IOException
      Throws:
      IOException

    • readPayload

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