Package io.netty.handler.codec.xml

Class XmlFrameDecoder

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.handler.codec.ByteToMessageDecoder

io.netty.handler.codec.xml.XmlFrameDecoder

All Implemented Interfaces:

ChannelHandler, ChannelInboundHandler

public class XmlFrameDecoder
extends ByteToMessageDecoder

A frame decoder for single separate XML based message streams.

A couple examples will better help illustrate what this decoder actually does.

Given an input array of bytes split over 3 frames like this:

 +-----+-----+-----------+
 | <an | Xml | Element/> |
 +-----+-----+-----------+
 

this decoder would output a single frame:

 +-----------------+
 | <anXmlElement/> |
 +-----------------+
 

Given an input array of bytes split over 5 frames like this:

 +-----+-----+-----------+-----+----------------------------------+
 | <an | Xml | Element/> | <ro | ot><child>content</child></root> |
 +-----+-----+-----------+-----+----------------------------------+
 

this decoder would output two frames:

 +-----------------+-------------------------------------+
 | <anXmlElement/> | <root><child>content</child></root> |
 +-----------------+-------------------------------------+
 

The byte stream is expected to be in UTF-8 character encoding or ASCII. The current implementation uses direct byte to char cast and then compares that char to a few low range ASCII characters like '<', '>' or '/'. UTF-8 is not using low range [0..0x7F] byte values for multibyte codepoint representations therefore fully supported by this implementation.

Please note that this decoder is not suitable for xml streaming protocols such as XMPP, where an initial xml element opens the stream and only gets closed at the end of the session, although this class could probably allow for such type of message flow with minor modifications.

Nested Class Summary

Nested classes/interfaces inherited from class io.netty.handler.codec.ByteToMessageDecoder

ByteToMessageDecoder.Cumulator

Nested classes/interfaces inherited from interface io.netty.channel.ChannelHandler

ChannelHandler.Sharable

Field Summary

Fields

Modifier and Type	Field	Description
private final int	maxFrameLength

Fields inherited from class io.netty.handler.codec.ByteToMessageDecoder

COMPOSITE_CUMULATOR, MERGE_CUMULATOR

Constructor Summary

Constructors

Constructor	Description
XmlFrameDecoder(int maxFrameLength)

Method Summary

Modifier and Type	Method	Description
protected void	decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out)	Decode the from one ByteBuf to an other.
private static ByteBuf	extractFrame(ByteBuf buffer, int index, int length)
private void	fail(long frameLength)
private static void	fail(ChannelHandlerContext ctx)
private static boolean	isCDATABlockStart(ByteBuf in, int i)
private static boolean	isCommentBlockStart(ByteBuf in, int i)
private static boolean	isValidStartCharForXmlElement(byte b)	Asks whether the given byte is a valid start char for an xml element name.

Methods inherited from class io.netty.handler.codec.ByteToMessageDecoder

actualReadableBytes, callDecode, channelInactive, channelRead, channelReadComplete, decodeLast, discardSomeReadBytes, handlerRemoved, handlerRemoved0, internalBuffer, isSingleDecode, setCumulator, setDiscardAfterReads, setSingleDecode, userEventTriggered

Methods inherited from class io.netty.channel.ChannelInboundHandlerAdapter

channelActive, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, handlerAdded, isSharable

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.netty.channel.ChannelHandler

handlerAdded

Field Details

maxFrameLength

private final int maxFrameLength

Constructor Details

XmlFrameDecoder

public XmlFrameDecoder(int maxFrameLength)

Method Details

decode

protected void decode(ChannelHandlerContext ctx,
 ByteBuf in,
 List<Object> out)
               throws Exception

Description copied from class: ByteToMessageDecoder

Decode the from one ByteBuf to an other. This method will be called till either the input ByteBuf has nothing to read when return from this method or till nothing was read from the input ByteBuf.

Specified by:

decode in class ByteToMessageDecoder

Parameters:

ctx - the ChannelHandlerContext which this ByteToMessageDecoder belongs to

in - the ByteBuf from which to read data

out - the List to which decoded messages should be added

Throws:

Exception - is thrown if an error occurs

fail

private void fail(long frameLength)

fail

private static void fail(ChannelHandlerContext ctx)

extractFrame

private static ByteBuf extractFrame(ByteBuf buffer,
 int index,
 int length)

isValidStartCharForXmlElement

private static boolean isValidStartCharForXmlElement(byte b)

Asks whether the given byte is a valid start char for an xml element name.

Please refer to the NameStartChar formal definition in the W3C XML spec for further info.

Parameters:

b - the input char

Returns:

true if the char is a valid start char

isCommentBlockStart

private static boolean isCommentBlockStart(ByteBuf in,
 int i)

isCDATABlockStart

private static boolean isCDATABlockStart(ByteBuf in,
 int i)