MessageCodec (Vert.x Stack - Docs 5.0.0.CR2 API)

Type Parameters:

S - the type of the message being sent

R - the type of the message being received.

All Known Implementing Classes:

ServiceExceptionMessageCodec
```
public interface MessageCodec<S,R>
```
A message codec allows a custom message type to be marshalled across the event bus.
Usually the event bus only allows a certain set of message types to be sent across the event bus, including primitive types, boxed primitive types, byte[], JsonObject, JsonArray, Buffer.
By specifying a message codec you can pass any other type across the event bus, e.g. POJOs.
With a message codec the type sent does not have to be the same as the type received, e.g. you could send a Buffer and have it be received as a JsonObject.
Instances of this class must be thread-safe as they may be used concurrently by different threads.

Author:

Tim Fox

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`R`	`decodeFromWire(int pos, Buffer buffer)`	Called by Vert.x when a message is decoded from the wire.
`void`	`encodeToWire(Buffer buffer, S s)`	Called by Vert.x when marshalling a message to the wire.
`String`	`name()`	The codec name.
`byte`	`systemCodecID()`	Used to identify system codecs.
`R`	`transform(S s)`	If a message is sent locally across the event bus, this method is called to transform the message from the sent type S to the received type R

- Method Detail
  - encodeToWire
```
void encodeToWire(Buffer buffer,
                  S s)
```
    Called by Vert.x when marshalling a message to the wire.
    
    Parameters:
    
    buffer - the message should be written into this buffer
    
    s - the message that is being sent
  - decodeFromWire
```
R decodeFromWire(int pos,
                 Buffer buffer)
```
    Called by Vert.x when a message is decoded from the wire.
    
    Parameters:
    
    pos - the position in the buffer where the message should be read from.
    
    buffer - the buffer to read the message from
    
    Returns:
    
    the read message
  - transform
```
R transform(S s)
```
    If a message is sent locally across the event bus, this method is called to transform the message from the sent type S to the received type R
    
    Parameters:
    
    s - the sent message
    
    Returns:
    
    the transformed message
  - name
```
String name()
```
    The codec name. Each codec must have a unique name. This is used to identify a codec when sending a message and for unregistering codecs.
    
    Returns:
    
    the name
  - systemCodecID
```
byte systemCodecID()
```
    Used to identify system codecs. Should always return -1 for a user codec.
    
    Returns:
    
    -1 for a user codec.