Package org.apache.mina.filter.codec
Class CumulativeProtocolDecoder
java.lang.Object
org.apache.mina.filter.codec.ProtocolDecoderAdapter
org.apache.mina.filter.codec.CumulativeProtocolDecoder
- All Implemented Interfaces:
ProtocolDecoder
- Direct Known Subclasses:
ObjectSerializationDecoder
A
ProtocolDecoder
that cumulates the content of received
buffers to a cumulative buffer to help users implement decoders.
If the received ByteBuffer
is only a part of a message.
decoders should cumulate received buffers to make a message complete or
to postpone decoding until more buffers arrive.
Here is an example decoder that decodes CRLF terminated lines into
Command
objects:
public class CRLFTerminatedCommandLineDecoder extends CumulativeProtocolDecoder { private Command parseCommand(ByteBuffer in) { // Convert the bytes in the specified buffer to a // Command object. ... } protected boolean doDecode(IoSession session, ByteBuffer in, ProtocolDecoderOutput out) throws Exception { // Remember the initial position. int start = in.position(); // Now find the first CRLF in the buffer. byte previous = 0; while (in.hasRemaining()) { byte current = in.get(); if (previous == '\r' invalid input: '&'invalid input: '&' current == '\n') { // Remember the current position and limit. int position = in.position(); int limit = in.limit(); try { in.position(start); in.limit(position); // The bytes between in.position() and in.limit() // now contain a full CRLF terminated line. out.write(parseCommand(in.slice())); } finally { // Set the position to point right after the // detected line and set the limit to the old // one. in.position(position); in.limit(limit); } // Decoded one line; CumulativeProtocolDecoder will // call me again until I return false. So just // return true until there are no more lines in the // buffer. return true; } previous = current; } // Could not find CRLF in the buffer. Reset the initial // position to the one we recorded above. in.position(start); return false; } }
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
decode
(IoSession session, ByteBuffer in, ProtocolDecoderOutput out) Cumulates content of in into internal buffer and forwards decoding request todoDecode(IoSession, ByteBuffer, ProtocolDecoderOutput)
.void
Releases the cumulative buffer used by the specified session.protected abstract boolean
doDecode
(IoSession session, ByteBuffer in, ProtocolDecoderOutput out) Implement this method to consume the specified cumulative buffer and decode its content into message(s).Methods inherited from class org.apache.mina.filter.codec.ProtocolDecoderAdapter
finishDecode
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Constructor Details
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CumulativeProtocolDecoder
protected CumulativeProtocolDecoder()Creates a new instance.
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Method Details
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decode
Cumulates content of in into internal buffer and forwards decoding request todoDecode(IoSession, ByteBuffer, ProtocolDecoderOutput)
. doDecode() is invoked repeatedly until it returns false and the cumulative buffer is compacted after decoding ends.- Throws:
IllegalStateException
- if your doDecode() returned true not consuming the cumulative buffer.Exception
- if the read data violated protocol specification
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doDecode
protected abstract boolean doDecode(IoSession session, ByteBuffer in, ProtocolDecoderOutput out) throws Exception Implement this method to consume the specified cumulative buffer and decode its content into message(s).- Parameters:
in
- the cumulative buffer- Returns:
- true if and only if there's more to decode in the buffer and you want to have doDecode method invoked again. Return false if remaining data is not enough to decode, then this method will be invoked again when more data is cumulated.
- Throws:
Exception
- if cannot decode in.
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dispose
Releases the cumulative buffer used by the specified session. Please don't forget to call super.dispose( session ) when you override this method.- Specified by:
dispose
in interfaceProtocolDecoder
- Overrides:
dispose
in classProtocolDecoderAdapter
- Throws:
Exception
- if failed to dispose all resources
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