First sent message is not garbage collected per session.

[Michelberger, Joerg]

Hi there,

I did a heap dump of my application containing MINA 2.0.0RC1 and found a lot of 
my messages not garbage collected.
I use ProtocolCodecFilter. 
After a investigation with VisualVM I found my already sent messages stucking 
in a DefaultWriteRequest as attribute message. 
The DefaultWriteRequest is attribute writeRequest in 
ProtocolCodecFilter$ProtocolEncoderOutputImpl. 
ProtocolCodecFilter$ProtocolEncoderOutputImpl stucks with key ENCODER_OUT in 
the sessions attribute map. 
WriteRequest in ProtocolCodecFilter$ProtocolEncoderOutputImpl is not released 
after flushing...
The attribute ENCODER_OUT is never removed from attributes.
Seems that only first Message stucks ProtocolEncoderOutputImpl as result of 
constructor call of ProtocolCodecFilter line 543. ProtocolEncoderOutputImpl is 
stored for later usage in ProtocolCodecFilter line 298, but only for providing 
public void write(Object encodedMessage) API.

Hmm, ProtocolEncoderOutputImpl should store not the whole WriteRequest, only 
significant data.
If there are Login data inside this message, all data is stored for session 
lifetime in memory.

ProtocolCodecFilter.java
    private ProtocolEncoderOutput getEncoderOut(IoSession session,
        NextFilter nextFilter, WriteRequest writeRequest) {
        ProtocolEncoderOutput out = (ProtocolEncoderOutput) 
session.getAttribute(ENCODER_OUT);
        
        if (out == null) {
            // Create a new instance, and stores it into the session
            out = new ProtocolEncoderOutputImpl(session, nextFilter, 
writeRequest);
            session.setAttribute(ENCODER_OUT, out);
        }
        
        return out;
    }

Regards
        Jörg Michelberger