Package io.netty.handler.codec.mqtt

Class MqttDecoder

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.handler.codec.ByteToMessageDecoder

io.netty.handler.codec.ReplayingDecoder<MqttDecoder.DecoderState>

io.netty.handler.codec.mqtt.MqttDecoder

All Implemented Interfaces:

ChannelHandler, ChannelInboundHandler

public final class MqttDecoder
extends ReplayingDecoder<MqttDecoder.DecoderState>

Decodes Mqtt messages from bytes, following the MQTT protocol specification v3.1 or v5.0, depending on the version specified in the CONNECT message that first goes through the channel.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static enum	MqttDecoder.DecoderState	States of the decoder.
private static final class	MqttDecoder.Result<T>

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 int	bytesRemainingInVariablePart
private final int	maxBytesInMessage
private final int	maxClientIdLength
private MqttFixedHeader	mqttFixedHeader
private Object	variableHeader

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

COMPOSITE_CUMULATOR, MERGE_CUMULATOR

Constructor Summary

Constructors

Constructor	Description
MqttDecoder()
MqttDecoder(int maxBytesInMessage)
MqttDecoder(int maxBytesInMessage, int maxClientIdLength)

Method Summary

Modifier and Type	Method	Description
protected void	decode(ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out)	Decode the from one ByteBuf to an other.
private static byte[]	decodeByteArray(ByteBuf buffer)
private static MqttDecoder.Result<MqttConnAckVariableHeader>	decodeConnAckVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer)
private static MqttDecoder.Result<MqttConnectPayload>	decodeConnectionPayload(ByteBuf buffer, int maxClientIdLength, MqttConnectVariableHeader mqttConnectVariableHeader)
private static MqttDecoder.Result<MqttConnectVariableHeader>	decodeConnectionVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer)
private static MqttFixedHeader	decodeFixedHeader(ChannelHandlerContext ctx, ByteBuf buffer)	Decodes the fixed header.
private static int	decodeMessageId(ByteBuf buffer)
private static MqttDecoder.Result<MqttMessageIdAndPropertiesVariableHeader>	decodeMessageIdAndPropertiesVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer)
private static int	decodeMsbLsb(ByteBuf buffer)	numberOfBytesConsumed = 2.
private static MqttDecoder.Result<?>	decodePayload(ChannelHandlerContext ctx, ByteBuf buffer, MqttMessageType messageType, int bytesRemainingInVariablePart, int maxClientIdLength, Object variableHeader)	Decodes the payload.
private static MqttDecoder.Result<MqttProperties>	decodeProperties(ByteBuf buffer)
private static MqttDecoder.Result<ByteBuf>	decodePublishPayload(ByteBuf buffer, int bytesRemainingInVariablePart)
private MqttDecoder.Result<MqttPublishVariableHeader>	decodePublishVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer, MqttFixedHeader mqttFixedHeader)
private MqttDecoder.Result<MqttPubReplyMessageVariableHeader>	decodePubReplyMessage(ByteBuf buffer)
private MqttDecoder.Result<MqttReasonCodeAndPropertiesVariableHeader>	decodeReasonCodeAndPropertiesVariableHeader(ByteBuf buffer)
private static MqttDecoder.Result<String>	decodeString(ByteBuf buffer)
private static MqttDecoder.Result<String>	decodeString(ByteBuf buffer, int minBytes, int maxBytes)
private static MqttDecoder.Result<MqttSubAckPayload>	decodeSubackPayload(ByteBuf buffer, int bytesRemainingInVariablePart)
private static MqttDecoder.Result<MqttSubscribePayload>	decodeSubscribePayload(ByteBuf buffer, int bytesRemainingInVariablePart)
private static MqttDecoder.Result<MqttUnsubAckPayload>	decodeUnsubAckPayload(ChannelHandlerContext ctx, ByteBuf buffer, int bytesRemainingInVariablePart)
private static MqttDecoder.Result<MqttUnsubscribePayload>	decodeUnsubscribePayload(ByteBuf buffer, int bytesRemainingInVariablePart)
private static long	decodeVariableByteInteger(ByteBuf buffer)	See 1.5.5 Variable Byte Integer section of MQTT 5.0 specification for encoding/decoding rules
private MqttDecoder.Result<?>	decodeVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer, MqttFixedHeader mqttFixedHeader)	Decodes the variable header (if any)
private MqttMessage	invalidMessage(Throwable cause)
private static long	packInts(int a, int b)
private static int	unpackA(long ints)
private static int	unpackB(long ints)

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

callDecode, checkpoint, checkpoint, state, state

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

actualReadableBytes, 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

mqttFixedHeader

private MqttFixedHeader mqttFixedHeader

variableHeader

private Object variableHeader

bytesRemainingInVariablePart

private int bytesRemainingInVariablePart

maxBytesInMessage

private final int maxBytesInMessage

maxClientIdLength

private final int maxClientIdLength

Constructor Details

MqttDecoder

public MqttDecoder()

MqttDecoder

public MqttDecoder(int maxBytesInMessage)

MqttDecoder

public MqttDecoder(int maxBytesInMessage,
 int maxClientIdLength)

Method Details

decode

protected void decode(ChannelHandlerContext ctx,
 ByteBuf buffer,
 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

buffer - 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

invalidMessage

private MqttMessage invalidMessage(Throwable cause)

decodeFixedHeader

private static MqttFixedHeader decodeFixedHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

Decodes the fixed header. It's one byte for the flags and then variable bytes for the remaining length.

Parameters:

buffer - the buffer to decode from

Returns:

the fixed header

decodeVariableHeader

private MqttDecoder.Result<?> decodeVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer,
 MqttFixedHeader mqttFixedHeader)

Decodes the variable header (if any)

Parameters:

buffer - the buffer to decode from

mqttFixedHeader - MqttFixedHeader of the same message

Returns:

the variable header

decodeConnectionVariableHeader

private static MqttDecoder.Result<MqttConnectVariableHeader> decodeConnectionVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodeConnAckVariableHeader

private static MqttDecoder.Result<MqttConnAckVariableHeader> decodeConnAckVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodeMessageIdAndPropertiesVariableHeader

private static MqttDecoder.Result<MqttMessageIdAndPropertiesVariableHeader> decodeMessageIdAndPropertiesVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodePubReplyMessage

private MqttDecoder.Result<MqttPubReplyMessageVariableHeader> decodePubReplyMessage(ByteBuf buffer)

decodeReasonCodeAndPropertiesVariableHeader

private MqttDecoder.Result<MqttReasonCodeAndPropertiesVariableHeader> decodeReasonCodeAndPropertiesVariableHeader(ByteBuf buffer)

decodePublishVariableHeader

private MqttDecoder.Result<MqttPublishVariableHeader> decodePublishVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer,
 MqttFixedHeader mqttFixedHeader)

decodeMessageId

private static int decodeMessageId(ByteBuf buffer)

Returns:

messageId with numberOfBytesConsumed is 2

decodePayload

private static MqttDecoder.Result<?> decodePayload(ChannelHandlerContext ctx,
 ByteBuf buffer,
 MqttMessageType messageType,
 int bytesRemainingInVariablePart,
 int maxClientIdLength,
 Object variableHeader)

Decodes the payload.

Parameters:

buffer - the buffer to decode from

messageType - type of the message being decoded

bytesRemainingInVariablePart - bytes remaining

variableHeader - variable header of the same message

Returns:

the payload

decodeConnectionPayload

private static MqttDecoder.Result<MqttConnectPayload> decodeConnectionPayload(ByteBuf buffer,
 int maxClientIdLength,
 MqttConnectVariableHeader mqttConnectVariableHeader)

decodeSubscribePayload

private static MqttDecoder.Result<MqttSubscribePayload> decodeSubscribePayload(ByteBuf buffer,
 int bytesRemainingInVariablePart)

decodeSubackPayload

private static MqttDecoder.Result<MqttSubAckPayload> decodeSubackPayload(ByteBuf buffer,
 int bytesRemainingInVariablePart)

decodeUnsubAckPayload

private static MqttDecoder.Result<MqttUnsubAckPayload> decodeUnsubAckPayload(ChannelHandlerContext ctx,
 ByteBuf buffer,
 int bytesRemainingInVariablePart)

decodeUnsubscribePayload

private static MqttDecoder.Result<MqttUnsubscribePayload> decodeUnsubscribePayload(ByteBuf buffer,
 int bytesRemainingInVariablePart)

decodePublishPayload

private static MqttDecoder.Result<ByteBuf> decodePublishPayload(ByteBuf buffer,
 int bytesRemainingInVariablePart)

decodeString

private static MqttDecoder.Result<String> decodeString(ByteBuf buffer)

decodeString

private static MqttDecoder.Result<String> decodeString(ByteBuf buffer,
 int minBytes,
 int maxBytes)

decodeByteArray

private static byte[] decodeByteArray(ByteBuf buffer)

Returns:

the decoded byte[], numberOfBytesConsumed = byte[].length + 2

packInts

private static long packInts(int a,
 int b)

unpackA

private static int unpackA(long ints)

unpackB

private static int unpackB(long ints)

decodeMsbLsb

private static int decodeMsbLsb(ByteBuf buffer)

numberOfBytesConsumed = 2. return decoded result.

decodeVariableByteInteger

private static long decodeVariableByteInteger(ByteBuf buffer)

See 1.5.5 Variable Byte Integer section of MQTT 5.0 specification for encoding/decoding rules

Parameters:

buffer - the buffer to decode from

Returns:

result pack with a = decoded integer, b = numberOfBytesConsumed. Need to unpack to read them.

Throws:

DecoderException - if bad MQTT protocol limits Remaining Length

decodeProperties

private static MqttDecoder.Result<MqttProperties> decodeProperties(ByteBuf buffer)