Overview
When a message comes in to the ESB, the receiving transport selects a message builder based on the message's content type. It uses that builder to process the message's raw payload data and convert it into SOAP. Conversely, when sending a message out from the ESB, a message formatter is used to build the outgoing stream from the message. As with message builders, the message formatter is selected based on the message's content type. In a typical ESB routing scenario, here is the flow:
Configuring message builders and formatters
Message builders and formatters are specified in <ESB_HOME>/repository/conf/axis2/axis2.xml under the messageBuilders and messageFormatters configuration sections. The ESB has a few default message builders, so even if you do not specify them explicitly in axis2.xml, they will take effect when messages of those content types come into the ESB. If you want to use different builders, specify them in axis2.xml to override the defaults. The ESB does not have default message formatters, so it is important to specify all of them in the axis2.xml configuration. Following are the default message builders:
| Content type | Message Builder |
|---|---|
application/soap+xml | org.apache.axis2.builder.SOAPBuilder |
multipart/related | org.apache.axis2.builder.MIMEBuilder |
text/xml | org.apache.axis2.builder.SOAPBuilder |
application/xop+xml | org.apache.axis2.builder.MTOMBuilder |
application/xml | org.apache.axis2.builder.ApplicationXMLBuilder |
application/x-www-form-urlencoded | org.apache.axis2.builder.XFormURLEncodedBuilder |
Using message relay
If you want to enable message relay, so that messages of a specific content type are not built or formatted but simply pass through the ESB, you can specify the message relay builder (org.wso2.carbon.relay.BinaryRelayBuilder) for that content type. For more information, see Configuring Message Relay.
Handling messages with no content type
To ensure that messages with no content type are handled gracefully without causing errors, add the following to axis2.xml:
- In the parameters section:
<parameter name="defaultContentType" locked="false">empty/content</parameter> - In the message builders section:
<messageBuilder contentType="empty/content" class="org.wso2.carbon.relay.BinaryRelayBuilder"/> - In the message formatters section:
<messageFormatter contentType="empty/content" class="org.wso2.carbon.relay.ExpandingMessageFormatter"/>
Handling text/csv messages
There is no default builder or formatter for messages with the text/csv content type. If you just want to pass these messages through the ESB, you can configure the message relay builder and formatter. If you want to process these messages, you can access the content inside the request/response payload of CSV by configuring the org.apache.axis2.format.PlainTextBuilder and org.apache.axis2.format.PlainTextFormatter for the text/csv content type in axis2.xml. For example:
<messagebuilder contenttype="text/csv" class="org.apache.axis2.format.PlainTextBuilder"/> <messageformatter contenttype="text/csv" class="org.apache.axis2.format.PlainTextFormatter"/>
When a text/csv message comes into the ESB, the log will include an entry similar to the following, and you can observe that the CSV data is placed inside the payload:
[2013-05-09 13:59:03,478] INFO - LogMediator To: , WSAction: urn:mediate, SOAPAction: urn:mediate, MessageID: urn:uuid:5B9A211341DCC368241368088143463, Direction: request, Envelope: <?xml version='1.0' encoding='utf-8'?><soapenv:envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"><soapenv:body><text xmlns="http://ws.apache.org/commons/ns/payload">charitha,wso2,colombo chamara,wso2G,galle </text></soapenv:body></soapenv:envelope>