Top Description Fields Constructors Methods
io.netty.handler.codec.xml

public Class XmlFrameDecoder

extends ByteToMessageDecoder
Class Inheritance
Static Imports
io.netty.util.internal.ObjectUtil.checkPositive
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.

Field Summary

Modifier and TypeField and Description
private final int
maxFrameLength

Inherited from io.netty.handler.codec.ByteToMessageDecoder:
COMPOSITE_CUMULATORMERGE_CUMULATOR

Constructor Summary

AccessConstructor and Description
public
XmlFrameDecoder(int maxFrameLength)

Method Summary

Modifier and TypeMethod and Description
protected void
decode(ChannelHandlerContext
the ChannelHandlerContext which this ByteToMessageDecoder belongs to
ctx, ByteBuf
the ByteBuf from which to read data
in, List<Object>
the List to which decoded messages should be added
out)

Implements abstract io.netty.handler.codec.ByteToMessageDecoder.decode.

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(final ByteBuf in, final int i)

private static boolean
isCommentBlockStart(final ByteBuf in, final int i)

private static boolean

Returns:

true if the char is a valid start char
isValidStartCharForXmlElement(final byte
the input char
b)

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

Inherited from io.netty.handler.codec.ByteToMessageDecoder:
actualReadableBytescallDecodechannelInactivechannelReadchannelReadCompletedecodeLastdiscardSomeReadByteshandlerRemovedhandlerRemoved0internalBufferisSingleDecodesetCumulatorsetDiscardAfterReadssetSingleDecodeuserEventTriggered

Field Detail

maxFrameLengthback to summary
private final int maxFrameLength

Constructor Detail

XmlFrameDecoderback to summary
public XmlFrameDecoder(int maxFrameLength)

Method Detail

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

Implements abstract io.netty.handler.codec.ByteToMessageDecoder.decode.

Doc from io.netty.handler.codec.ByteToMessageDecoder.decode.

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.

Parameters
ctx:ChannelHandlerContext

the ChannelHandlerContext which this ByteToMessageDecoder belongs to

in:ByteBuf

the ByteBuf from which to read data

out:List<Object>

the List to which decoded messages should be added

Annotations
@Override
Exceptions
Exception:
is thrown if an error occurs
extractFrameback to summary
private static ByteBuf extractFrame(ByteBuf buffer, int index, int length)
failback to summary
private void fail(long frameLength)
failback to summary
private static void fail(ChannelHandlerContext ctx)
isCDATABlockStartback to summary
private static boolean isCDATABlockStart(final ByteBuf in, final int i)
isCommentBlockStartback to summary
private static boolean isCommentBlockStart(final ByteBuf in, final int i)
isValidStartCharForXmlElementback to summary
private static boolean isValidStartCharForXmlElement(final 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:byte

the input char

Returns:boolean

true if the char is a valid start char