Package org.jgroups

Class BytesMessage

    • Field Detail

      • array

        protected byte[] array
        The payload

      • offset

        protected int offset
        The index into the payload

      • length

        protected int length
        The number of bytes in the array

    • Constructor Detail

      • BytesMessage

        public BytesMessage()

      • BytesMessage

        public BytesMessage​(Address dest)
        Constructs a message given a destination address
        Parameters:
        dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.

      • BytesMessage

        public BytesMessage​(Address dest,
                    byte[] array)
        Constructs a message given a destination and source address and the payload byte array
        Parameters:
        dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.
        array - The payload. Note that this array must not be modified (e.g. buf[0]='x' is not allowed) since we don't copy the contents.

      • BytesMessage

        public BytesMessage​(Address dest,
                    byte[] array,
                    int offset,
                    int length)
        Constructs a message. The index and length parameters provide a reference to a byte array, rather than a copy, and refer to a subset of the array. This is important when we want to avoid copying. When the message is serialized, only the subset is serialized.

        Note that the byte array passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte array passed in as argument, and so we would retransmit a changed byte array !
        Parameters:
        dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.
        array - A reference to a byte array
        offset - The index into the byte array
        length - The number of bytes to be used from buf. Both index and length are checked for array index violations and an ArrayIndexOutOfBoundsException will be thrown if invalid

      • BytesMessage

        public BytesMessage​(Address dest,
                    java.lang.Object obj)
        Constructs a message given a destination and source address and the payload object
        Parameters:
        dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.
        obj - The object that will be marshalled into the byte array. Has to be serializable (e.g. implementing Serializable, Externalizable or Streamable, or be a basic type (e.g. Integer, Short etc)).

    • Method Detail

      • create

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

      • getType

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

      • 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

      • 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

      • getArray

        public 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.

      • setArray

        public BytesMessage setArray​(byte[] b,
                             int offset,
                             int length)
        Sets the internal array to point to a subset of a given array.

        Note that the byte array passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte array passed in as argument, and so we would retransmit a changed byte array !

        Parameters:
        b - The reference to a given array. If null, we'll reset the array to null
        offset - The initial position
        length - The number of bytes

      • setArray

        public BytesMessage setArray​(ByteArray buf)
        Sets the array

        Note that the byte array passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte array passed in as argument, and so we would retransmit a changed byte array !

      • setObject

        public BytesMessage setObject​(java.lang.Object obj)
        Takes an object and uses Java serialization to generate the byte array which is set in the message. Parameter 'obj' has to be serializable (e.g. implementing Serializable, Externalizable or Streamable, or be a basic type (e.g. Integer, Short etc)).

      • 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.

      • getObject

        public <T> T getObject​(java.lang.ClassLoader loader)
        Uses custom serialization to create an object from the array of the message. Note that this is dangerous when using your own classloader, e.g. inside of an application server ! Most likely, JGroups will use the system classloader to deserialize the array into an object, whereas (for example) a web application will want to use the webapp's classloader, resulting in a ClassCastException. The recommended way is for the application to use their own serialization and only pass byte array to JGroups.

        As of 3.5, a classloader can be passed in. It will be used first to find a class, before contacting the other classloaders in the list. If null, the default list of classloaders will be used.

        Returns:
        the object

      • size

        public int size()
        Description copied from interface: Message
        Returns the exact size of the marshalled message
        Specified by:
        size in interface Message
        Overrides:
        size in class BaseMessage
        Returns:
        The number of bytes for the marshalled message

      • copyPayload

        protected Message copyPayload​(Message copy)
        Copies the byte array. If offset and length are used (to refer to another array), the copy will contain only the subset that offset and length point to, copying the subset into the new copy.

        Note that for headers, only the arrays holding references to the headers are copied, not the headers themselves ! The consequence is that the headers array of the copy hold the *same* references as the original, so do *not* modify the headers ! If you want to change a header, copy it and call BaseMessage.putHeader(short,Header) again.

        Overrides:
        copyPayload in class BaseMessage

      • sizeOfPayload

        protected int sizeOfPayload()

      • writePayload

        public void writePayload​(java.io.DataOutput out)
                  throws java.io.IOException
        Throws:
        java.io.IOException

      • readPayload

        public void readPayload​(java.io.DataInput in)
                 throws java.io.IOException
        Throws:
        java.io.IOException

      • createMessage

        protected <T extends BytesMessage> T createMessage()