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Protocol Tables

In addition, since TCP and SSL are stream-oriented and Mule is message-oriented, some application protocol is needed to to define where each message begins and ends within the stream. The table below lists the built-in protocols, describing:

  • The XML tag used to specify them

  • Any XML attributes

  • How it defines a message when reading

  • Any processing it does while writing a message

XML tag Options Read Write Notes

<tcp:custom-class-loading-protocol>

rethrowExceptionOnRead, payloadOnly , maxMessageLength, classLoader-ref

Expects the message to begin with a 4-byte length (in DataOutput.writeInt() format)

Precedes the message with a 4-byte length (in DataOutput.writeInt() format)

Like the length protocol, but specifies a classloader used to deserialize objects

<tcp:custom-protocol>

rethrowExceptionOnRead, class, ref

varies

varies

Allows user-written protocols, for instance, to match existing TCP services.

<tcp:direct-protocol>

rethrowExceptionOnRead, payloadOnly

All currently available bytes

none

There are no explicit message boundaries.

<tcp:eof-protocol>

rethrowExceptionOnRead, payloadOnly

All bytes sent until the socket is closed

none

<tcp:length-protocol>

rethrowExceptionOnRead, payloadOnly , maxMessageLength

Expects the message to begin with a 4-byte length (in DataOutput.writeInt() format)

Precedes the message with a 4-byte length (in DataOutput.writeInt() format)

<tcp:safe-protocol

rethrowExceptionOnRead, payloadOnly , maxMessageLength Expects the message to begin with the string "You are using SafeProtocol" followed by a 4-byte length (in DataOutput.writeInt() format)

Expects the message to be preceded by the string "You are using SafeProtocol" followed by a 4-byte length (in DataOutput.writeInt() format)

Precedes the message with the string "You are using SafeProtocol" followed by a 4-byte length (in DataOutput.writeInt() format)

Somewhat safer than the length protocol because of the extra check. This is the default if no protocol is specified.

<tcp:streaming-protocol

rethrowExceptionOnRead

All bytes sent until the socket is closed

none

<tcp:xml-protocol>

rethrowExceptionOnRead

A message is an XML document that begins with an XML declaration

none

The XML declaration must occur in all messages

<tcp:xml-eof-protocol>

rethrowExceptionOnRead

A message is an XML document that begins with an XML declaration, or whatever remains at EOF

none

The XML declaration must occur in all messages

Protocol attributes:

name values default value notes

class

The name of the class that implements the custom protocol

See below for an example of writing a custom protocol

classLoader-ref

A reference to a Spring bean that contains the custom classloader

maxMessageLength

the maximum message length allowed

0 (no maximum )

A message longer than the maximum causes an exception to be thrown.

payloadOnly

true

If true, only the Mule message payload is sent or received. If false, the entire Mule message is sent or received.

Protocols that don’t support this attribute always process payloads

ref

A reference to a Spring bean that implements the custom protocol

rethrowExceptionOnRead

Whether to rethrow exception that occur trying to read from the socket

false

Setting this to "false" avoids logging stack traces when the remote socket is closed unexpectedly