Java Reference
In-Depth Information
A binding component converts a message that is bound to a specific protocol or transport
into the normalized form. Both BCs and SEs create a “delivery channel” to the normalized
message router. A BC is generally used to enable the pluggability of an external protocol or
format. For example, you use a BPEL SE to execute a BPEL engine because the message
format BPEL requires is XML. The JBI runtime doesn't have to do anything special to convert
an XML instance message coming into the bus as SOAP/HTTP because that's what a BPEL
process instance expects.
But if you need to do some conversion based on the protocol or transport of the message,
you may need to employ a BC. BCs exist for File, LDAP, JMS, HTTP, JDBC, CICS, DCOM,
CORBA, XMPP, and more. These protocols require specific message formats, and that's why
there are BCs for them. You can download these BCs for free from either the OpenESB or
ServiceMix websites and then plug them into your bus to enable your message exchange us-
ing one of these protocols.
Normalized message router
The normalized message router (NMR) mediates the message exchange between SEs and BCs
within the framework. The NMR is at the heart of the bus and allows services to interoper-
ate by passing messages between all of the components in the system. The message route is
determined by the NMR, and the normalized message is translated into the format for the spe-
cific BC that is being invoked. SEs and BCs all communicate with the NMR via a pipe called
a delivery channel.
A normalized message itself consists of two parts: the abstract XML message and the message
metadata, also called message context data.
The abstract message defines the structure and constraints for valid messages, written in XML
schema, as represented in the abstract message type in a WSDL.
The second part of a normalized message, the message context data, allows plug-in and system
components to provide additional information about a message during its processing. This in-
formation might include the following kinds of items:
▪ Security tokens provided by SAML or another mechanism
▪ Context information provided by a given protocol, such as a path
▪ Transaction management information
▪ Data from other components
The NMR is bidirectional, so it is used to send requests and responses.
