Hi all,
We have identified three scenarios when considering content aware support
in Next Gen ESB . These can be categorized as a pure pass thru scenario
where payload is not touched , reading the content without modifying
scenario and reading and modifying the content. So we came up of initial
design and implementation of the content reading part. We have come up
with different message readers for different content types . For
example, for the XML message XMLReader is used and for the JSON Messages
JSONReader is used. Message readers are pluggable via OSGI service.
[image: reader_implementation.png]
Reader Registration
-
Gateway core consists of in memory registry which keeps registered
MessageReaders according to content type.
-
Message readers are registered via OSGI services.
-
JSON message reader and XML message reader are implemented as two
different OSGI bundles.
-
CarbonMessage is supported with reading content as InputStream and write
content via OutputStream.
Message Flow
-
Need to specify the portion of the message that needs to be read via
XPath or JSONPath according to the content type.
-
When message hits the content aware mediator it checks weather message
is already read if so then it takes MessageDataSource which is data holder
for already read message inputstream according contentType.Else it gets the
matching reader from reader registry and read the input stream and load the
inputstream into MessageDataSource.
-
XPath and JSONPath are evaluated using MessageDataSource
-
Serialize data from MessageDataSource to CarbonMessage before sending to
the transport level after mediation.
XML Reading
-
Axiom is used for represent XML messages as OMElements
-
Axiom uses StAX API for read and write XML messages which is inherently
supports deferred building concept.
-
AxiomXpath is used for evaluate XPath and it used Jaxen as underlying
XPath library.
-
XPath libraries are pluggable.
JSON Reading
-
Jayway library is used for represent JSONPath.
-
Underlying JSON library is Jackson.
-
Jackson has JSONParser and JSONGenerator which are similar to
StreamingXMLReader and Writer in StAX API and can read, write events in
streaming manner.
- Jackson supports data binding as well.
Thanks
--
Best Regards
Isuru Ranawaka
M: +94714629880
Blog : http://isurur.blogspot.com/
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