Adapter Technical Note Technical Note #005: Adapter Headers

Transcription

1 Adapter Technical Note Technical Note #005: Adapter Headers This document describes the Adapter Headers and how to use them within the BPEL process. Contents 1. What is an Adapter Header? What are the File Adapter Header elements? What are the AQ Adapter Header elements? What are the JMS Adapter Header elements? What are the configuration steps to get and set the Adapter Header elements? What are the various use cases of the Adapter Header?... 7 Page 1

2 1. What is an Adapter Header? The Adapter Header is used to capture the metadata to support Inbound and Outbound Interactions. The Adapter message contains the Header part and the Payload part. These headers can be set within the BPEL process before invoking an Outbound Interaction. An example would be the setting of output file name parameter within the FileAdapterOutboundHeader.wsdl for dynamically specifying the output file. In addition, you can extract the Header attributes from an incoming Adapter message (as part of Inbound Interaction) and perform appropriate actions within the BPEL process. An example would be the extraction of MessageID attribute from an incoming JMS Adapter message (JMSAdapterInboundHeader.wsdl) and using it within the BPEL process to define correlation sets. Note: Only the FTP/Files, JMS and AQ Adapters support Header elements. 2. What are the File Adapter Header elements? File Adapter Inbound Header Elements filename Directory Name of the input file Directory location of the input file File Adapter Outbound Header Elements filename Name of the output file 3. What are the AQ Adapter Header elements? AQ Adapter Inbound Header Elements MessageID Attempts Priority Correlation Enqueuetime The unique handle for a message. This value is generated by AQ. No of attempts made to deliver the message to AQ Consumer Priority of the message AQ allows assigning a corelation id, a string identifier to each message, thus providing a means of retrieving specific messages at a later time. Time elapsed since the message was enqueued Page 2

3 AQ Adapter Outbound Header Elements MessageID Recipient List Priority Correlation Expiration ExceptionQueue The unique handle for a message. The AQ Message Producer can set this value via AQ Headers and is generated by the underlying AQ application if it is not set. No of attempts made to deliver the message to AQ Consumer Priority of the message AQ allows assigning a corelation id, a string identifier to each message, thus providing a means of retrieving specific messages at a later time. This is set by the AQ Message Producer and is used for filtering of messages by the AQ Message Consumer. Time when the message should expire Queue for moving the undelivered and expired messages. 4. What are the JMS Adapter Header elements? JMS Adapter Inbound Header Elements (JMS Message Consumer) These are standard JMS Headers JMSType JMSDeliveryMode JMSExpiration JMSPriority JMSMessageID JMSTimestamp JMSCorrelationId JMSRedelivered Type of the JMS message Byte ot Text. Set to persistent or non-persistent mode by the JMS Producer. The JMS Provider sets it to non-persistent by default. Duration of the message before expiration set by the JMS Producer. 1 indicates no expiration. Number between 0 and 9 set by the JMS Producer. Larger numbers represent higher priority. The JMS Provider automatically sets it to the default priority of the JMS Queue or Topic if not set by the JMS Producer. Unique message identifier set by the underlying JMS application. Timestamp when message was sent to the JMS provider for forwarding. This is automatically set by the JMSProvider. Used by both Producers and Consumers for linking the response message with the request message. This is an optional attribute Set by the JMS Provider to indicate that the Provider has Page 3

4 tried to send this message once before to the consumer and has failed. JMS Adapter Outbound Header Elements (JMS Producer) These are standard JMS Headers JMSType JMSCorrelationId Type of the JMS message Byte ot Text. Set by the JMS Producers. Used by the JMS Consumers for filtering requests and for correlating an asynchronous request with response. This is an optional attribute 5. What are the configuration steps to get and set the Adapter Header elements? Header information can also be translated into BPEL variables using the Adapter tab when defining BPEL activities that send or receive messages. This tab enables you to create header variables. You can create header variables in Invoke, Receive, Reply, and Pick - OnMessage branch activities. Information passing through header variables is Adapter specific. The following steps illustrate how to extract the Adapter Header elements from an incoming Adapter message. Drag & drop a Partner Link and configure it for an Inbound Adapter Service (JCA Inbound Interaction). Drag & drop a receive activity and point it to the Partner Link. Select createinstance and autogenerate the input Global Variable. Page 4

5 Navigate to the Adapters tab of the receive activity. Select the browse option to create Header variables. This brings up the Variable Chooser pop-up window. Select the Create option and specify the name of the Adapter Header Variable. Select the MessageType for the Variable and choose the browse option to point to the AQ Inbound Header definition. The Header Variable Dequeue_Header_Variable is set to the Header message of the aqadapterinbound Header.wsdl Page 5

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7 6. What are the various use cases of the Adapter Header? The Adapter Header can be used to correlate two asynchronous AQ/JMS Adapter messages. The CorrelationID attribute of the outgoing Adapter message ( AQ/JMS Adapter Outbound Header) can be set to the MessageID of the incoming Adapter message (AQ/JMS Adapter Inbound Header) for modeling a requestresponse scenario. The Adapter Header can be used to dynamically specify the name of the output file for the File Writer Operation (File Adapter Outbound Header) Page 7