Message

java.lang.Object
- fabric.messages.Message<R,E>

Type Parameters:

N - The kind of node that can send messages of this type.

R - The response type

E - The exception type that may occur at the remote node while handling the message.

Direct Known Subclasses:

AbortTransactionMessage, AllocateMessage, CommitTransactionMessage, DirtyReadMessage, DissemReadMessage, GetCertChainMessage, InterWorkerStalenessMessage, MakePrincipalMessage, ObjectUpdateMessage, PrepareTransactionMessage, ReadMessage, RemoteCallMessage, StalenessCheckMessage, TakeOwnershipMessage
```
public abstract class Message<R extends Message.Response,E extends FabricException>
extends java.lang.Object
```
Messages provide an interface for serializing requests and responses. The Message class itself provides facilities for serialization and deserialization, while the concrete subclasses give the structure of each type of message.

Messages are intended to be used in a synchronous, call-return style. To support this, each Message type is bound to a specific Response type. On the sender side, this allows type safety in the send method, for example:
```
 ReadMessage.Response r = new ReadMessage(...).send(...);
 
```
while on the receiver side, type safety is enforced by only accepting R in the respond(...) method.

Messages use two instances of the visitor pattern, one for Messages bound for the store (MessageToStore) and one for Messages bound for the worker (MessageToWorker). These interfaces would be subclasses of Message, except that some message types (e.g. CommitTransactionMessage) go to both, and Java doesn't support multiple inheritance.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected static class`	`Message.MessageType` This enum gives a mapping between message types and ordinals.
`static class`	`Message.NoException` Concrete message implementations may use this class to indicate that no exceptions should be thrown during message processing.
`static interface`	`Message.Response` Marker interface for Message responses.

Field Summary

Fields
Modifier and Type	Field and Description
`protected java.lang.Class<E>`	`exceptionClass` The class of Exceptions that may be thrown in response to this Message
`protected Message.MessageType`	`messageType` The `MessageType` corresponding to this class.

Constructor Summary

Constructors
Modifier Constructor and Description

protected Message(Message.MessageType messageType, java.lang.Class<E> exceptionClass)
Constructs a message of the given MessageType

Constructors
Modifier	Constructor and Description
`protected`	`Message(Message.MessageType messageType, java.lang.Class<E> exceptionClass)` Constructs a message of the given `MessageType`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract R`	`dispatch(RemoteIdentity<RemoteWorker> client, MessageHandler handler)` Visitor method.
`protected <T> T`	`readObject(java.io.DataInput in, java.lang.Class<T> type)` Deserialize a java object from a DataOutput
`protected static Object._Proxy`	`readRef(java.lang.Class<?> type, java.io.DataInput in)` Deserializes a fabric object reference.
`protected abstract R`	`readResponse(java.io.DataInput in)` Creates a Response message of the appropriate type using the provided `DataOutput`
`static Message<?,?>`	`receive(java.io.DataInput in)` Read a Message from the given `DataInput`
`void`	`respond(java.io.DataOutput out, FabricException e)` Send a response to this message that indicates an exception.
`void`	`respond(java.io.DataOutput out, Message.Response response)` Send a successful response this message.
`R`	`send(SubSocket<?> s)` Sends this message to the given node and awaits a response.
`protected abstract void`	`writeMessage(java.io.DataOutput out)` Writes this message out on the given output stream.
`protected void`	`writeObject(java.io.DataOutput out, java.lang.Object o)` Serialize a java object to a DataOutput
`protected void`	`writeRef(Object._Proxy ref, java.io.DataOutput out)` Serializes a fabric object reference.
`protected abstract void`	`writeResponse(java.io.DataOutput out, R response)` Writes a Response message of the appropriate type using the provided `DataOutput`.

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

- Field Detail
  - messageType
```
protected final Message.MessageType messageType
```
    The MessageType corresponding to this class.
  - exceptionClass
```
protected final java.lang.Class<E extends FabricException> exceptionClass
```
    The class of Exceptions that may be thrown in response to this Message
- Constructor Detail
  - Message
```
protected Message(Message.MessageType messageType,
                  java.lang.Class<E> exceptionClass)
```
    Constructs a message of the given MessageType
    
    Parameters:
    
    exceptionClass - TODO
    
    exceptionClass - TODO
- Method Detail
  - send
```
public final R send(SubSocket<?> s)
             throws java.io.IOException,
                    E extends FabricException
```
    Sends this message to the given node and awaits a response.
    
    Returns:
    
    the reply from the node.
    
    Throws:
    
    E - if an error occurs at the remote node while handling the message.
    
    java.io.IOException - in the event of a communications failure.
    
    E extends FabricException
  - dispatch
```
public abstract R dispatch(RemoteIdentity<RemoteWorker> client,
                           MessageHandler handler)
                    throws ProtocolError,
                           E extends FabricException
```
    Visitor method.
    
    Parameters:
    
    client - the node that is issuing the request.
    
    handler - the handler to which this message is to be dispatched.
    
    Throws:
    
    ProtocolError
    
    E extends FabricException
  - receive
```
public static Message<?,?> receive(java.io.DataInput in)
                            throws java.io.IOException
```
    Read a Message from the given DataInput
    
    Throws:
    
    java.io.IOException - If a malformed message is sent, or in the case of a failure in the DataInput provided.
  - respond
```
public void respond(java.io.DataOutput out,
                    Message.Response response)
             throws java.io.IOException
```
    Send a successful response this message.
    
    Parameters:
    
    out - the channel on which to send the response
    
    response - the response to send.
    
    Throws:
    
    java.io.IOException - if the provided DataOutput fails.
  - respond
```
public void respond(java.io.DataOutput out,
                    FabricException e)
             throws java.io.IOException
```
    Send a response to this message that indicates an exception.
    
    Parameters:
    
    out - the channel on which to send the response
    
    e - the exception to send
    
    Throws:
    
    java.io.IOException - if the provided DataOutput fails.
  - writeRef
```
protected void writeRef(Object._Proxy ref,
                        java.io.DataOutput out)
                 throws java.io.IOException
```
    Serializes a fabric object reference.
    
    Throws:
    
    java.io.IOException
  - readRef
```
protected static Object._Proxy readRef(java.lang.Class<?> type,
                                       java.io.DataInput in)
                                throws java.io.IOException
```
    Deserializes a fabric object reference.
    
    Parameters:
    
    type - The type of the reference being read. This must be the interface corresponding to the Fabric type, and not the _Proxy or _Impl classes.
    
    Throws:
    
    java.io.IOException
  - writeObject
```
protected void writeObject(java.io.DataOutput out,
                           java.lang.Object o)
                    throws java.io.IOException
```
    Serialize a java object to a DataOutput
    
    Throws:
    
    java.io.IOException
  - readObject
```
protected <T> T readObject(java.io.DataInput in,
                           java.lang.Class<T> type)
                    throws java.io.IOException
```
    Deserialize a java object from a DataOutput
    
    Throws:
    
    java.io.IOException
  - writeMessage
```
protected abstract void writeMessage(java.io.DataOutput out)
                              throws java.io.IOException
```
    Writes this message out on the given output stream.
    
    Throws:
    
    java.io.IOException - if the DataOutput fails.
  - readResponse
```
protected abstract R readResponse(java.io.DataInput in)
                           throws java.io.IOException
```
    Creates a Response message of the appropriate type using the provided DataOutput
    
    Throws:
    
    java.io.IOException - if the response is malformed, or if the DataInput fails.
  - writeResponse
```
protected abstract void writeResponse(java.io.DataOutput out,
                                      R response)
                               throws java.io.IOException
```
    Writes a Response message of the appropriate type using the provided DataOutput.
    
    Throws:
    
    java.io.IOException - if the DataOutput fails.

Class Message<R extends Message.Response,E extends FabricException>

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

messageType

exceptionClass

Constructor Detail

Message

Method Detail

send

dispatch

receive

respond

respond

writeRef

readRef

writeObject

readObject

writeMessage

readResponse

writeResponse