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Short Description
JMSWriter Attributes
Best Practices
See also

Short Description

JMSWriter converts Clover data records into JMS messages.

Component Data output Input ports Output ports Transformation Transf. required Java CTL Auto-propagated metadata
JMSWriterjms messages10



Port typeNumberRequiredDescriptionMetadata
For data recordsAny


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
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
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


JMSWriter receives Clover 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 Clover 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.


Writing Records to JMS Queue

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


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.

JMS ConnectionMyJMSConnection
Message body fielde.g. field1

Best Practices

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

See also

JMS Connections
Common Properties of Components
Specific Attribute Types
Common Properties of Writers
Writers Comparison