Version

    JMSWriter

    Short Description
    Ports
    Metadata
    JMSWriter Attributes
    Details
    Examples
    Best Practices
    See also

    Short Description

    JMSWriter converts CloverDX data records into JMS messages.

    ComponentData outputInput portsOutput portsTransformationTransf. requiredJavaCTLAuto-propagated metadata
    JMSWriterjms messages10✓⨯✓⨯⨯

    Ports

    Port typeNumberRequiredDescriptionMetadata
    Input0✓For data recordsAny

    Metadata

    JMSWriter does not propagate metadata.

    JMSWriter has no metadata templates.

    Metadata on the input port may contain a field specified in the Message body field attribute.

    JMSWriter Attributes

    AttributeReqDescriptionPossible values
    Basic
    JMS connectionyesID of the JMS connection to be used. See JMS Connections. 
    Processor code Transformation of records to JMS messages written in the graph in Java. 
    Processor URL 

    Name of an external file, including the path, containing the transformation of records to JMS messages written in Java.

    		 
    Processor class 

    Name of an external class defining the transformation of records to JMS messages. The default processor value (org.jetel.component.jms. DataRecord2JmsMsgProperties) is sufficient for most cases. It produces javax.jms.TextMessage.

    		DataRecord2JmsMsgProperties (default) | other class
    Processor source charset 

    Encoding of external file containing the transformation in Java.

    The default encoding depends on DEFAULT_SOURCE_CODE_CHARSET in defaultProperties.

    		UTF-8 | other encoding
    Advanced
    Message body field 

    Name of the field of metadata from which the body of the message should be gotten and sent out. This attribute is used by the default processor implementation (JmsMsg2DataRecordProperties). If no Message body field is specified, the field whose name is bodyField will be used as a resource for the body of the message contents. If no field for the body of the message is contained in metadata (either explicitly specified or the default one), the processor tries to set a field named bodyField, but it's silently ignored if such field doesn't exist in output record metadata. The other fields from metadata serve as resources of message properties with the same names as field names.

    		bodyField (default) | other name

    Details

    JMSWriter receives CloverDX data records, converts them into JMS messages and sends these messages out. Component uses a processor transformation which implements a DataRecord2JmsMsg interface or inherits from a DataRecord2JmsMsgBase superclass. Methods of DataRecord2JmsMsg interface are described below.

    Details on threads are described in Details in JMSReader.

    Message Body, Message Header etc.

    Data inserted into the body or header of a message depends on the implementation of the Processor class. The default implementation is org.jetel.component.jms.DataRecord2JmsMsgProperties. The message body may be filled with textual representation of one field of the record. You can specify name of such field by the component attribute Message body field.

    All the other fields are saved using string properties in the message header. Property names are same as field names. Values contain textual representation of field values. Last message has same format as all the others. Terminating message is not used.

    Java Interfaces for JMSWriter

    The transformation implements methods of the DataRecord2JmsMsg interface and inherits other common methods from the Transform interface. See Common Java Interfaces. You can use Public CloverDX API too.

    Following are the methods of DataRecord2JmsMsg interface:

    • void init(DataRecordMetadata metadata, Session session, Properties props)

      Initializes the processor.

    • void preExecute(Session session)

      This is also an initialization method, which is invoked before each separate graph run. Contrary to the init() procedure, only resources for this graph run should be allocated here. All resources allocated here should be released in the postExecute() method.

      session may be used for creation of JMS messages. Each graph execution has its own session opened. Thus the session set in the init() method is usable only during the first execution of the graph instance.

    • Message createMsg(DataRecord record)

      Transforms data record to JMS message. Is called for all data records.

    • Message createLastMsg()

      This method is called after last record and is supposed to return a message terminating the JMS output. If it returns null, no terminating message is sent. Since 2.8.

    • String getErrorMsg()

      Returns an error message.

    • Message createLastMsg(DataRecord record) (deprecated)

      This method is not called explicitly since 2.8. Use createLastMsg() instead.

    Examples

    Writing Records to JMS Queue

    There is a message queue clover-queue on localhost:61616. Write 5 records into the message queue.

    Solution

    Create a JMS Connection MyJMSConnection. The details are described in the example Read Text Message from Message Queue in documentation on JMSReader.

    Configure the JMSWriter component.

    AttributeValue
    JMS ConnectionMyJMSConnection
    Message body fielde.g. field1

    Best Practices

    If Processor URL is used, we recommend users to explicitly specify Processor source charset.