Message

java.lang.Object
- org.jgroups.Message

All Implemented Interfaces:

Streamable
```
public class Message
extends java.lang.Object
implements Streamable
```
A Message encapsulates data sent to members of a group. It contains among other things the address of the sender, the destination address, a payload (byte buffer) and a list of headers. Headers are added by protocols on the sender side and removed by protocols on the receiver's side.
The byte buffer can point to a reference, and we can subset it using index and length. However, when the message is serialized, we only write the bytes between index and length.

Since:

2.0

Author:

Bela Ban

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class Message.Flag

static class Message.TransientFlag

Nested Classes
Modifier and Type	Class and Description
`static class`	`Message.Flag`
`static class`	`Message.TransientFlag`

Field Summary

Fields
Modifier and Type	Field and Description
`protected byte[]`	`buf` The payload
`protected Address`	`dest_addr`
`static Message.Flag`	`DONT_BUNDLE` Deprecated.
`protected short`	`flags`
`protected Header[]`	`headers` All headers are placed here
`protected int`	`length` The number of bytes in the buffer (usually buf.length is buf not equal to null).
`static Message.Flag`	`NO_FC` Deprecated.
`static Message.Flag`	`NO_RELAY` Deprecated.
`static Message.Flag`	`NO_RELIABILITY` Deprecated.
`static Message.Flag`	`NO_TOTAL_ORDER` Deprecated.
`protected int`	`offset` The index into the payload (usually 0)
`static Message.Flag`	`OOB` Deprecated.
`static Message.TransientFlag`	`OOB_DELIVERED` Deprecated.
`static Message.Flag`	`RSVP` Deprecated.
`static Message.Flag`	`SCOPED` Deprecated.
`protected Address`	`src_addr`
`protected byte`	`transient_flags`

Constructor Summary

Constructors
Constructor and Description
`Message()`
`Message(Address dest)` Constructs a Message given a destination Address
`Message(Address dest, Address src, byte[] buf)` Constructs a Message given a destination Address, a source Address and the payload byte buffer
`Message(Address dest, Address src, byte[] buf, int offset, int length)` Constructs a message.
`Message(Address dest, Address src, java.lang.Object obj)` Constructs a Message given a destination Address, a source Address and the payload Object
`Message(Address dest, byte[] buf)`
`Message(Address dest, byte[] buf, int offset, int length)`
`Message(Address dest, java.lang.Object obj)`
`Message(boolean create_headers)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Message`	`clearFlag(Message.Flag... flags)` Clears a number of flags in a message
`Message`	`clearTransientFlag(Message.TransientFlag... flags)`
`Message`	`copy()`
`Message`	`copy(boolean copy_buffer)` Create a copy of the message.
`Message`	`copy(boolean copy_buffer, boolean copy_headers)` Create a copy of the message.
`Message`	`copy(boolean copy_buffer, short starting_id)` Doesn't copy any headers except for those with ID >= copy_headers_above
`Message`	`copy(boolean copy_buffer, short starting_id, short... copy_only_ids)` Copies a message.
`protected static Header[]`	`createHeaders(int size)`
`Address`	`dest()`
`Message`	`dest(Address new_dest)`
`static java.lang.String`	`flagsToString(short flags)`
`byte[]`	`getBuffer()` Returns a copy of the buffer if offset and length are used, otherwise a reference.
`Address`	`getDest()`
`short`	`getFlags()` Returns the internal representation of flags.
`Header`	`getHeader(short id)`
`java.util.Map<java.lang.Short,Header>`	`getHeaders()` Returns a reference to the headers hashmap, which is immutable.
`int`	`getLength()` Returns the number of bytes in the buffer
`int`	`getNumHeaders()`
`java.lang.Object`	`getObject()`
`java.lang.Object`	`getObject(java.lang.ClassLoader loader)` Uses custom serialization to create an object from the buffer of the message.
`int`	`getOffset()` Returns the offset into the buffer at which the data starts
`byte[]`	`getRawBuffer()` Returns a reference to the payload (byte buffer).
`short`	`getScope()`
`Address`	`getSrc()`
`short`	`getTransientFlags()`
`boolean`	`isFlagSet(Message.Flag flag)` Checks if a given flag is set
`static boolean`	`isFlagSet(short flags, Message.Flag flag)`
`boolean`	`isTransientFlagSet(Message.TransientFlag flag)`
`static boolean`	`isTransientFlagSet(short flags, Message.TransientFlag flag)`
`Message`	`makeReply()`
`java.lang.String`	`printHeaders()`
`java.lang.String`	`printObjectHeaders()`
`Message`	`putHeader(short id, Header hdr)` Puts a header given an ID into the hashmap.
`Message`	`putHeaderIfAbsent(short id, Header hdr)` Puts a header given a key into the map, only if the key doesn't exist yet
`void`	`readFrom(java.io.DataInput in)` Read the state of the current object (including superclasses) from instream Note that the input stream must not be closed
`int`	`readFromSkipPayload(ByteArrayDataInputStream in)` Reads the message's contents from an input stream, but skips the buffer and instead returns the position (offset) at which the buffer starts
`protected static Header`	`readHeader(java.io.DataInput in)`
`Message`	`setBuffer(Buffer buf)` Note that the byte[] buffer passed as argument must not be modified.
`Message`	`setBuffer(byte[] b)` Note that the byte[] buffer passed as argument must not be modified.
`Message`	`setBuffer(byte[] b, int offset, int length)` Sets the internal buffer to point to a subset of a given buffer. Note that the byte[] buffer passed as argument must not be modified.
`void`	`setDest(Address new_dest)`
`Message`	`setFlag(Message.Flag... flags)` Sets a number of flags in a message
`Message`	`setFlag(short flag)` Sets the flags from a short.
`Message`	`setObject(java.lang.Object obj)` Takes an object and uses Java serialization to generate the byte[] buffer which is set in the message.
`Message`	`setScope(short scope)`
`void`	`setSrc(Address new_src)`
`Message`	`setTransientFlag(Message.TransientFlag... flags)` Same as `setFlag(Flag...)` except that transient flags are not marshalled
`Message`	`setTransientFlag(short flag)`
`boolean`	`setTransientFlagIfAbsent(Message.TransientFlag flag)` Atomically checks if a given flag is set and - if not - sets it.
`long`	`size()` Returns the exact size of the marshalled message.
`Address`	`src()`
`Message`	`src(Address new_src)`
`java.lang.String`	`toString()`
`static java.lang.String`	`transientFlagsToString(short flags)`
`protected static void`	`writeHeader(Header hdr, java.io.DataOutput out)`
`void`	`writeTo(java.io.DataOutput out)` Streams all members (dest and src addresses, buffer and headers) to the output stream.
`void`	`writeToNoAddrs(Address src, java.io.DataOutput out, short... excluded_headers)` Writes the message to the output stream, but excludes the dest and src addresses unless the src address given as argument is different from the message's src address

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

- Field Detail
  - dest_addr
```
protected Address dest_addr
```
  - src_addr
```
protected Address src_addr
```
  - buf
```
protected byte[] buf
```
    The payload
  - offset
```
protected int offset
```
    The index into the payload (usually 0)
  - length
```
protected int length
```
    The number of bytes in the buffer (usually buf.length is buf not equal to null).
  - headers
```
protected volatile Header[] headers
```
    All headers are placed here
  - flags
```
protected volatile short flags
```
  - transient_flags
```
protected volatile byte transient_flags
```
  - OOB
```
@Deprecated
public static final Message.Flag OOB
```
    Deprecated.
  - DONT_BUNDLE
```
@Deprecated
public static final Message.Flag DONT_BUNDLE
```
    Deprecated.
  - NO_FC
```
@Deprecated
public static final Message.Flag NO_FC
```
    Deprecated.
  - SCOPED
```
@Deprecated
public static final Message.Flag SCOPED
```
    Deprecated.
  - NO_RELIABILITY
```
@Deprecated
public static final Message.Flag NO_RELIABILITY
```
    Deprecated.
  - NO_TOTAL_ORDER
```
@Deprecated
public static final Message.Flag NO_TOTAL_ORDER
```
    Deprecated.
  - NO_RELAY
```
@Deprecated
public static final Message.Flag NO_RELAY
```
    Deprecated.
  - RSVP
```
@Deprecated
public static final Message.Flag RSVP
```
    Deprecated.
  - OOB_DELIVERED
```
@Deprecated
public static final Message.TransientFlag OOB_DELIVERED
```
    Deprecated.
- Constructor Detail
  - Message
```
public Message(Address dest)
```
    Constructs a Message given a destination Address
    
    Parameters:
    
    dest - Address of receiver. If it is null then the message sent to the group. Otherwise, it contains a single destination and is sent to that member.
  - Message
```
public Message(Address dest,
               Address src,
               byte[] buf)
```
    Constructs a Message given a destination Address, a source Address and the payload byte buffer
    
    Parameters:
    
    dest - Address of receiver. If it is null then the message sent to the group. Otherwise, it contains a single destination and is sent to that member.
    
    src - Address of sender
    
    buf - Message to be sent. Note that this buffer must not be modified (e.g. buf[0]=0 is not allowed), since we don't copy the contents on clopy() or clone().
  - Message
```
public Message(Address dest,
               byte[] buf)
```
  - Message
```
public Message(Address dest,
               Address src,
               byte[] buf,
               int offset,
               int length)
```
    Constructs a message. The index and length parameters allow to provide a reference to a byte buffer, rather than a copy, and refer to a subset of the buffer. This is important when we want to avoid copying. When the message is serialized, only the subset is serialized.
    Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !
    
    Parameters:
    
    dest - Address of receiver. If it is null then the message sent to the group. Otherwise, it contains a single destination and is sent to that member.
    
    src - Address of sender
    
    buf - A reference to a byte buffer
    
    offset - The index into the byte buffer
    
    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
  - Message
```
public Message(Address dest,
               byte[] buf,
               int offset,
               int length)
```
  - Message
```
public Message(Address dest,
               Address src,
               java.lang.Object obj)
```
    Constructs a Message given a destination Address, a source Address and the payload Object
    
    Parameters:
    
    dest - Address of receiver. If it is null then the message sent to the group. Otherwise, it contains a single destination and is sent to that member.
    
    src - Address of sender
    
    obj - The object will be marshalled into the byte buffer. Obj has to be serializable (e.g. implementing Serializable, Externalizable or Streamable, or be a basic type (e.g. Integer, Short etc)). ! The resulting buffer must not be modified (e.g. buf[0]=0 is not allowed), since we don't copy the contents on clopy() or clone().
  - Message
```
public Message(Address dest,
               java.lang.Object obj)
```
  - Message
```
public Message()
```
  - Message
```
public Message(boolean create_headers)
```
- Method Detail
  - getDest
```
public Address getDest()
```
  - dest
```
public Address dest()
```
  - setDest
```
public void setDest(Address new_dest)
```
  - dest
```
public Message dest(Address new_dest)
```
  - getSrc
```
public Address getSrc()
```
  - src
```
public Address src()
```
  - setSrc
```
public void setSrc(Address new_src)
```
  - src
```
public Message src(Address new_src)
```
  - getRawBuffer
```
public byte[] getRawBuffer()
```
    Returns a reference to the payload (byte buffer). Note that this buffer should not be modified as we do not copy the buffer on copy() or clone(): the buffer of the copied message is simply a reference to the old buffer.
    Even if offset and length are used: we return the entire buffer, not a subset.
  - getBuffer
```
public final byte[] getBuffer()
```
    Returns a copy of the buffer if offset and length are used, otherwise a reference.
    
    Returns:
    
    byte array with a copy of the buffer.
  - setBuffer
```
public final Message setBuffer(byte[] b)
```
    Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !
  - setBuffer
```
public final Message setBuffer(byte[] b,
                               int offset,
                               int length)
```
    Sets the internal buffer to point to a subset of a given buffer.
    Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !
    
    Parameters:
    
    b - The reference to a given buffer. If null, we'll reset the buffer to null
    
    offset - The initial position
    
    length - The number of bytes
  - setBuffer
```
public final Message setBuffer(Buffer buf)
```
    Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !
  - getOffset
```
public int getOffset()
```
    Returns the offset into the buffer at which the data starts
  - getLength
```
public int getLength()
```
    Returns the number of bytes in the buffer
  - getHeaders
```
public java.util.Map<java.lang.Short,Header> getHeaders()
```
    Returns a reference to the headers hashmap, which is immutable. Any attempt to modify the returned map will cause a runtime exception
  - printHeaders
```
public java.lang.String printHeaders()
```
  - getNumHeaders
```
public int getNumHeaders()
```
  - setObject
```
public final Message setObject(java.lang.Object obj)
```
    Takes an object and uses Java serialization to generate the byte[] buffer 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 final java.lang.Object getObject()
```
  - getObject
```
public final java.lang.Object getObject(java.lang.ClassLoader loader)
```
    Uses custom serialization to create an object from the buffer 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 buffer 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[] buffer 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
  - setFlag
```
public Message setFlag(Message.Flag... flags)
```
    Sets a number of flags in a message
    
    Parameters:
    
    flags - The flag or flags
    
    Returns:
    
    A reference to the message
  - setTransientFlag
```
public Message setTransientFlag(Message.TransientFlag... flags)
```
    Same as setFlag(Flag...) except that transient flags are not marshalled
    
    Parameters:
    
    flags - The flag
  - setFlag
```
public Message setFlag(short flag)
```
    Sets the flags from a short. Not recommended (use setFlag(org.jgroups.Message.Flag...) instead), as the internal representation of flags might change anytime.
    
    Parameters:
    
    flag -
    
    Returns:
  - setTransientFlag
```
public Message setTransientFlag(short flag)
```
  - getFlags
```
public short getFlags()
```
    Returns the internal representation of flags. Don't use this, as the internal format might change at any time ! This is only used by unit test code
    
    Returns:
  - getTransientFlags
```
public short getTransientFlags()
```
  - clearFlag
```
public Message clearFlag(Message.Flag... flags)
```
    Clears a number of flags in a message
    
    Parameters:
    
    flags - The flags
    
    Returns:
    
    A reference to the message
  - clearTransientFlag
```
public Message clearTransientFlag(Message.TransientFlag... flags)
```
  - isFlagSet
```
public static boolean isFlagSet(short flags,
                                Message.Flag flag)
```
  - isFlagSet
```
public boolean isFlagSet(Message.Flag flag)
```
    Checks if a given flag is set
    
    Parameters:
    
    flag - The flag
    
    Returns:
    
    Whether or not the flag is currently set
  - isTransientFlagSet
```
public static boolean isTransientFlagSet(short flags,
                                         Message.TransientFlag flag)
```
  - isTransientFlagSet
```
public boolean isTransientFlagSet(Message.TransientFlag flag)
```
  - setTransientFlagIfAbsent
```
public boolean setTransientFlagIfAbsent(Message.TransientFlag flag)
```
    Atomically checks if a given flag is set and - if not - sets it. When multiple threads concurrently call this method with the same flag, only one of them will be able to set the flag
    
    Parameters:
    
    flag -
    
    Returns:
    
    True if the flag could be set, false if not (was already set)
  - setScope
```
public Message setScope(short scope)
```
  - getScope
```
public short getScope()
```
  - putHeader
```
public Message putHeader(short id,
                         Header hdr)
```
    Puts a header given an ID into the hashmap. Overwrites potential existing entry.
  - putHeaderIfAbsent
```
public Message putHeaderIfAbsent(short id,
                                 Header hdr)
```
    Puts a header given a key into the map, only if the key doesn't exist yet
  - getHeader
```
public Header getHeader(short id)
```
  - copy
```
public Message copy()
```
  - copy
```
public Message copy(boolean copy_buffer)
```
    Create a copy of the message. If offset and length are used (to refer to another buffer), the copy will contain only the subset offset and length point to, copying the subset into the new copy.
    
    Parameters:
    
    copy_buffer -
    
    Returns:
    
    Message with specified data
  - copy
```
public Message copy(boolean copy_buffer,
                    boolean copy_headers)
```
    Create a copy of the message. If offset and length are used (to refer to another buffer), the copy will contain only the subset 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 putHeader(short,Header) again.
    
    Parameters:
    
    copy_buffer -
    
    copy_headers - Copy the headers
    
    Returns:
    
    Message with specified data
  - copy
```
public Message copy(boolean copy_buffer,
                    short starting_id)
```
    Doesn't copy any headers except for those with ID >= copy_headers_above
    
    Parameters:
    
    copy_buffer -
    
    starting_id -
    
    Returns:
    
    A message with headers whose ID are >= starting_id
  - copy
```
public Message copy(boolean copy_buffer,
                    short starting_id,
                    short... copy_only_ids)
```
    Copies a message. Copies only headers with IDs >= starting_id or IDs which are in the copy_only_ids list
    
    Parameters:
    
    copy_buffer -
    
    starting_id -
    
    copy_only_ids -
    
    Returns:
  - makeReply
```
public Message makeReply()
```
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - printObjectHeaders
```
public java.lang.String printObjectHeaders()
```
  - writeTo
```
public void writeTo(java.io.DataOutput out)
             throws java.lang.Exception
```
    Streams all members (dest and src addresses, buffer and headers) to the output stream.
    
    Specified by:
    
    writeTo in interface Streamable
    
    Parameters:
    
    out -
    
    Throws:
    
    java.lang.Exception
  - writeToNoAddrs
```
public void writeToNoAddrs(Address src,
                           java.io.DataOutput out,
                           short... excluded_headers)
                    throws java.lang.Exception
```
    Writes the message to the output stream, but excludes the dest and src addresses unless the src address given as argument is different from the message's src address
    
    Parameters:
    
    src -
    
    out -
    
    excluded_headers - Don't marshal headers that are part of excluded_headers
    
    Throws:
    
    java.lang.Exception
  - readFrom
```
public void readFrom(java.io.DataInput in)
              throws java.lang.Exception
```
    Description copied from interface: Streamable
    
    Read the state of the current object (including superclasses) from instream Note that the input stream must not be closed
    
    Specified by:
    
    readFrom in interface Streamable
    
    Throws:
    
    java.lang.Exception
  - readFromSkipPayload
```
public int readFromSkipPayload(ByteArrayDataInputStream in)
                        throws java.lang.Exception
```
    Reads the message's contents from an input stream, but skips the buffer and instead returns the position (offset) at which the buffer starts
    
    Throws:
    
    java.lang.Exception
  - size
```
public long size()
```
    Returns the exact size of the marshalled message. Uses method size() of each header to compute the size, so if a Header subclass doesn't implement size() we will use an approximation. However, most relevant header subclasses have size() implemented correctly. (See org.jgroups.tests.SizeTest).
    
    Returns:
    
    The number of bytes for the marshalled message
  - flagsToString
```
public static java.lang.String flagsToString(short flags)
```
  - transientFlagsToString
```
public static java.lang.String transientFlagsToString(short flags)
```
  - writeHeader
```
protected static void writeHeader(Header hdr,
                                  java.io.DataOutput out)
                           throws java.lang.Exception
```
    Throws:
    
    java.lang.Exception
  - readHeader
```
protected static Header readHeader(java.io.DataInput in)
                            throws java.lang.Exception
```
    Throws:
    
    java.lang.Exception
  - createHeaders
```
protected static Header[] createHeaders(int size)
```

Class Message

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

dest_addr

src_addr

buf

offset

length

headers

flags

transient_flags

OOB

DONT_BUNDLE

NO_FC

SCOPED

NO_RELIABILITY

NO_TOTAL_ORDER

NO_RELAY

RSVP

OOB_DELIVERED

Constructor Detail

Message

Message

Message

Message

Message

Message

Message

Message

Message

Method Detail

getDest

dest

setDest

dest

getSrc

src

setSrc

src

getRawBuffer

getBuffer

setBuffer

setBuffer

setBuffer

getOffset

getLength

getHeaders

printHeaders

getNumHeaders

setObject

getObject

getObject

setFlag

setTransientFlag

setFlag

setTransientFlag

getFlags

getTransientFlags

clearFlag

clearTransientFlag

isFlagSet

isFlagSet

isTransientFlagSet

isTransientFlagSet

setTransientFlagIfAbsent

setScope

getScope

putHeader

putHeaderIfAbsent

getHeader

copy

copy

copy

copy

copy

makeReply