JMSWriter

Development > Component reference > Writers > JMSWriter

Short description

Short description

JMSWriter converts CloverDX data records into JMS messages.

Data output	Input ports	Output ports	Transformation	Transf. required	Java	CTL	Auto-propagated metadata
jms messages	1	0	✓	⨯	✓	⨯	⨯

Data output

Input ports

Output ports

Transformation

Transf. required

Java

CTL

Auto-propagated metadata

jms messages

✓

⨯

✓

⨯

Ports

Port type	Number	Required	Description	Metadata
Input	0	✓	For data records	Any

Port type

Number

Required

Description

Metadata

Input

✓

For data records

Any

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

Attribute Req Description Possible values

Attribute	Req	Description	Possible values
Basic
JMS connection	yes	ID 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

Basic

JMS connection

yes

ID 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.

Attribute	Value
JMS Connection	MyJMSConnection
Message body field	e.g. field1

Attribute

Value

JMS Connection

MyJMSConnection

Message body field

e.g. field1

Best practices

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

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JMSWriter

Short description

Ports

Metadata

JMSWriter attributes

Details

Message Body, Message Header etc.

Java interfaces for JMSWriter

Examples

Writing Records to JMS Queue

Solution

Best practices

See also