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 ByteToMessageDecoder

ByteToMessageDecoder.Cumulator

Nested classes/interfaces inherited from interface 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 final boolean	strictUtf8Validation
private CharsetDecoder	utf8Decoder
private Object	variableHeader

Fields inherited from class ByteToMessageDecoder

COMPOSITE_CUMULATOR, MERGE_CUMULATOR

Constructor Summary

Constructors

Constructor	Description
MqttDecoder()
MqttDecoder(int maxBytesInMessage)
MqttDecoder(int maxBytesInMessage, int maxClientIdLength)
MqttDecoder(int maxBytesInMessage, int maxClientIdLength, boolean strictUtf8Validation)	Creates a new MqttDecoder.

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 MqttConnAckVariableHeader	decodeConnAckVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer)
private MqttConnectPayload	decodeConnectionPayload(ByteBuf buffer, int maxClientIdLength, MqttConnectVariableHeader mqttConnectVariableHeader)
private 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 MqttMessageIdAndPropertiesVariableHeader	decodeMessageIdAndPropertiesVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer)
private static int	decodeMsbLsb(ByteBuf buffer)	numberOfBytesConsumed = 2.
private Object	decodePayload(ChannelHandlerContext ctx, ByteBuf buffer, MqttMessageType messageType, int maxClientIdLength, Object variableHeader)	Decodes the payload.
private MqttDecoder.Result<MqttProperties>	decodeProperties(ByteBuf buffer)
private ByteBuf	decodePublishPayload(ByteBuf buffer)
private MqttPublishVariableHeader	decodePublishVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer, MqttFixedHeader mqttFixedHeader)
private MqttPubReplyMessageVariableHeader	decodePubReplyMessage(ByteBuf buffer)
private MqttReasonCodeAndPropertiesVariableHeader	decodeReasonCodeAndPropertiesVariableHeader(ByteBuf buffer)
private MqttDecoder.Result<String>	decodeString(ByteBuf buffer)
private MqttDecoder.Result<String>	decodeString(ByteBuf buffer, int minBytes, int maxBytes)
private MqttSubAckPayload	decodeSubackPayload(ByteBuf buffer)
private MqttSubscribePayload	decodeSubscribePayload(ByteBuf buffer)
private MqttUnsubAckPayload	decodeUnsubAckPayload(ChannelHandlerContext ctx, ByteBuf buffer)
private MqttUnsubscribePayload	decodeUnsubscribePayload(ByteBuf buffer)
private static long	decodeVariableByteInteger(ByteBuf buffer)	See 1.5.5 Variable Byte Integer section of MQTT 5.0 specification for encoding/decoding rules
private Object	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 String	readStrictUtf8(ByteBuf buffer, int length)	Reads length bytes from buffer and decodes them as a strictly validated UTF-8 Encoded String per MQTT 3.1.1 and MQTT 5.0.
private static int	unpackA(long ints)
private static int	unpackB(long ints)
private void	validateNoBytesRemain(int numberOfBytesConsumed)

Methods inherited from class ReplayingDecoder

callDecode, checkpoint, checkpoint, state, state

Methods inherited from class ByteToMessageDecoder

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

Methods inherited from class ChannelInboundHandlerAdapter

channelActive, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught

Methods inherited from class ChannelHandlerAdapter

ensureNotSharable, handlerAdded, isSharable

Methods inherited from class Object

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

Methods inherited from interface 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

strictUtf8Validation

private final boolean strictUtf8Validation

utf8Decoder

private CharsetDecoder utf8Decoder

Constructor Details

MqttDecoder

public MqttDecoder()

MqttDecoder

public MqttDecoder(int maxBytesInMessage)

MqttDecoder

public MqttDecoder(int maxBytesInMessage,
 int maxClientIdLength)

MqttDecoder

public MqttDecoder(int maxBytesInMessage,
 int maxClientIdLength,
 boolean strictUtf8Validation)

Creates a new MqttDecoder.

Parameters:

maxBytesInMessage - the maximum number of bytes a decoded message may consume.

maxClientIdLength - the maximum length of the Client Identifier (CONNECT payload).

strictUtf8Validation - if true (default), every UTF-8 Encoded String is validated according to MQTT 3.1.1 and MQTT 5.0 malformed UTF-8 sequences (including surrogates and overlong forms) and an embedded U+0000 are rejected as a Malformed Packet. If false, the legacy behaviour is preserved, malformed bytes are silently replaced with U+FFFD and U+0000 is accepted.

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 Object 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 MqttConnectVariableHeader decodeConnectionVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodeConnAckVariableHeader

private MqttConnAckVariableHeader decodeConnAckVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodeMessageIdAndPropertiesVariableHeader

private MqttMessageIdAndPropertiesVariableHeader decodeMessageIdAndPropertiesVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodePubReplyMessage

private MqttPubReplyMessageVariableHeader decodePubReplyMessage(ByteBuf buffer)

decodeReasonCodeAndPropertiesVariableHeader

private MqttReasonCodeAndPropertiesVariableHeader decodeReasonCodeAndPropertiesVariableHeader(ByteBuf buffer)

decodePublishVariableHeader

private MqttPublishVariableHeader decodePublishVariableHeader(ChannelHandlerContext ctx,
 ByteBuf buffer,
 MqttFixedHeader mqttFixedHeader)

decodeMessageId

private static int decodeMessageId(ByteBuf buffer)

Returns:

messageId with numberOfBytesConsumed is 2

decodePayload

private Object decodePayload(ChannelHandlerContext ctx,
 ByteBuf buffer,
 MqttMessageType messageType,
 int maxClientIdLength,
 Object variableHeader)

Decodes the payload.

Parameters:

buffer - the buffer to decode from

messageType - type of the message being decoded

variableHeader - variable header of the same message

Returns:

the payload

decodeConnectionPayload

private MqttConnectPayload decodeConnectionPayload(ByteBuf buffer,
 int maxClientIdLength,
 MqttConnectVariableHeader mqttConnectVariableHeader)

decodeSubscribePayload

private MqttSubscribePayload decodeSubscribePayload(ByteBuf buffer)

decodeSubackPayload

private MqttSubAckPayload decodeSubackPayload(ByteBuf buffer)

decodeUnsubAckPayload

private MqttUnsubAckPayload decodeUnsubAckPayload(ChannelHandlerContext ctx,
 ByteBuf buffer)

decodeUnsubscribePayload

private MqttUnsubscribePayload decodeUnsubscribePayload(ByteBuf buffer)

decodePublishPayload

private ByteBuf decodePublishPayload(ByteBuf buffer)

validateNoBytesRemain

private void validateNoBytesRemain(int numberOfBytesConsumed)

decodeString

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

decodeString

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

readStrictUtf8

private String readStrictUtf8(ByteBuf buffer,
 int length)

Reads length bytes from buffer and decodes them as a strictly validated UTF-8 Encoded String per MQTT 3.1.1 and MQTT 5.0. Throws a DecoderException if the sequence is malformed or contains U+0000.

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 MqttDecoder.Result<MqttProperties> decodeProperties(ByteBuf buffer)