XMLTransformation node

This topic contains the following sections:

Purpose

Use the XMLTransformation node to transform an XML message to another form of XML message, according to the rules provided by an XSL (eXtensible Stylesheet Language) style sheet.

You can specify the location of the style sheet to apply to this transformation in three ways:

  • Use node properties, which ensures that the transformation that is defined by this single style sheet is applied to every message that is processed by this node.
  • Use the content of the XML data within the message itself, which transforms the message according to a style sheet that the message itself defines.
  • Set a value within the LocalEnvironment folder. You must set this value before the XMLTransformation node (for example, in a Compute node). You can therefore use a variety of inputs to determine which style sheet to use for this message, such as the content of the message data or a value in a database.

An XSLT (eXtensible Stylesheet Language for Transformations) compiler is used for the transformation if the style sheet is not embedded within the message and the node cache level (node property Stylesheet Cache Level) is greater than zero. If the XSLT is cached, the performance is improved because the XSLT is not parsed every time it is used.

If the prologue of the input message body contains an XML encoding declaration, the XMLTransformation node ignores the encoding, and always uses the CodedCharSetId in the message property folder to decode the message.

The XMLTransformation node is represented in the workbench by the following icon:

XMLTransformation node icon

Using this node in a message flow

For an example of how to use this node, consider two news organizations that exchange information on a regular basis. One might be a television station, the other a newspaper. Although the information is similar, the vocabulary used by the two is different. This node can transform one format to the other by applying the rules of the specified style sheet. If you specify the style sheet in the message (either the XML data or the LocalEnvironment), the same node can perform both transformations.

Look at the XMLT sample for more details about how to use the XMLTransformation node.

Deployed and non-deployed style sheets

You can use style sheets in two different ways with the XMLTransformation node:
Deployed style sheets
Deployed style sheets are style sheets that you import into a broker archive (bar) file and deploy to target systems. Deployed style sheets are managed by WebSphere Message Broker. A principal style sheet is the root style sheet that is referenced in a message flow; for example, a reference to a principal style sheet in the Eclipse workspace, C:\\project1\a\b.xsl must be specified as a/b.xsl (or ./a/b.xsl). A principal style sheet can reference (include or import) its descendent style sheets.
Non-deployed style sheets
Non-deployed style sheets are style sheets that you store in a location where the XMLTransformation node can access them. Non-deployed styles sheets are not managed by WebSphere Message Broker.
For more information, see Migration of style sheets and XML files.

Deployment of deployed style sheets or XML files

Before you configure the XMLTransformation node, understand how to work with style sheets. (A style sheet can refer to another XML file as well as a style sheet.) To use deployed style sheets or XML files, take the following steps:
  1. Make sure that the files have the correct file name extensions.

    Style sheets that are to be deployed must have either .xsl or .xslt as their file extension, and XML files to be deployed must have .xml as their file extension.

  2. Import the files into the Eclipse workspace.

    All style sheets and XML files that are to be deployed must be imported into an Eclipse workspace project. Location-dependent descendant style sheets, or XML files that are to be deployed, must be placed in the correct directory structure relative to their parent style sheets. You should not put in the Eclipse workspace location-dependent descendants that you do not want to deploy.

  3. Make sure that all references to the files are relative.

    Generally, all references to a deployed style sheet must be made relative, no matter where they appear. A reference to a principal style sheet should be made relative to the root of the relevant Eclipse workspace project.

    The only exception is when you specify a principal style sheet as the Stylesheet Name property on an XMLTransformation node, you can use an absolute path that points to the correct directory structure in the Eclipse workspace. If the principal style sheet is found, the system resets the node property automatically to the correct relative value. It also performs an automatic deployment of the principal style sheet, together with all its location-dependent descendant style sheets that are available in the relevant Eclipse workspace project. All references to the location-dependent descendant style sheets (or XML files) of a principal style sheet must be made relative to the location of their parent style sheets; for example, if style sheet, //project1/a/b.xsl references style sheet, //project1/a/c/d.xsl, the reference must be changed to c/d.xsl (or ./c/d.xsl).

  4. Handle non-deployed child style sheets or XML files.

    Style sheets can refer to other style sheets. If you have a relatively-referenced child style sheet (or XML file) that is not to be deployed, yet its parent is, make sure that the child style sheet is placed in the right location under broker work path/XSL/external (broker work path/XML/external). A broker automatically associates the execution group deployed storage tree, broker work path/XSL/external, and broker work path/XML/external tree, together. That means, for example, that the broker automatically performs a search in broker work path/XML/external/a/b directory for a reference of document (b/c.xml) in the deployed principal style sheet a/style.xsl if b/c.xml is not found in the broker’s deployed storage. Relative path references must also be used for files that have been deployed but which are not available in the workspace.

  5. Deploy the files.

    Deploy manually only those style sheets or XML files that are not picked up by the system (the Message Brokers Toolkit provides warnings about these files). If you click Browse for the node, or provide the full path of the location of the style sheet in the Eclipse workspace, the style sheet is included automatically in the bar file.

    To deploy manually, add the files to be deployed to a broker archive (refer to Adding files to a broker archive and to Adding keywords to XSL stylesheets) and deploy the broker archive.

    For every execution group that uses the XMLTransformation node, you can perform the following actions:
    • Include the style sheet in the broker work path/XSL/external directory on the broker; do not include the style sheet in the bar file.

      If a style sheet in the broker work path/XSL/external directory shares the same path and name with a deployed style sheet, the deployed style sheet is used.

    • Include the style sheet in the bar file and deploy the bar file. If multiple bar files include the same style sheet name, the style sheet from the last bar file that was deployed is used.
    • Deploy the style sheet in its own bar file. If the bar files use XMLTransformation nodes, but do not include the style sheet, the Message Brokers Toolkit issues warning messages.
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Configuring the XMLTransformation node

When you have put an instance of the XMLTransformation node into a message flow, you can configure it. To display its properties, right-click the node and click Properties. (If you double-click the XMLTransformation node, you open the XSL Selection dialog box.)

All mandatory properties for which you must enter a value (those that do not have a default value defined) are marked with an asterisk.

Configure the XMLTransformation node as follows:

  1. Optional: On the Description tab, enter a short description, a long description, or both. You can also rename the node on this tab.
  2. On the Stylesheet tab, to specify a non-deployed style sheet using node properties, enter the required value for Stylesheet Name. This value is ignored if stylesheet information is found in a preferred location (determined by the selection priority values that you have set).
    There are three ways to specify a principal style sheet:
    • Click Browse next to the Stylesheet Name property. The identified principal style sheet and all its relatively-referenced descendant style sheets are added automatically to the bar file when you add a message flow to a bar file (as long as both they and their parent style sheets are available).
    • To identify an already deployed, or ready to be deployed, style sheet, use the Stylesheet Name property, and leave the Stylesheet Directory property blank.
    • In the Message Flow editor, drag an .xslt file onto the XMLTransformation node; the Stylesheet Name is set automatically.
  3. On the Advanced tab:
    1. If the stylesheet identification is fully qualified, Stylesheet Directory is ignored; otherwise, the value that you set in this property is added to the beginning of the specification, regardless of where it is found.
    2. In Stylesheet Cache Level, specify the number of compiled or parsed style sheets that are stored in this instance of the node; the default value is 5. The stylesheet cache is retained for the life of the node and is cleared when the node is deleted from the flow, when the flow is deleted, or when the execution group is stopped.

      If you change a cached style sheet (by redeploying or replacing the file in the file system), the XMLTransformation node that is holding the cache replaces the cached version with the modified (latest) version before a new message is processed. However, if you are changing several style sheets, stop relevant message flows before you make any changes. If you do not stop the relevant message flows before you make the changes, the order of the changes cannot be guaranteed by running message flows, which might cause an incompatibility between the style sheets that are changed. Use the mqsireload command to reload a style sheet; however, this command does not prevent incompatibility.

    3. Select values for the XML Embedded Stylesheet Selection Priority, Message Environment Selection Priority, and Broker Node Attribute Selection Priority properties. The values that you set determine the order in which alternative locations are searched for the stylesheet information. The highest priority setting is 1. The default order is:
      1. XML Embedded Selection Priority, which has a default value of 1. The node searches the message XML data for stylesheet location information. For example, the XML data might contain:
        <?xml-stylesheet type="text/xsl" href="foo.xsl"?>
      2. Message Environment Selection Priority, which has a default value of 2. The node searches the LocalEnvironment that is associated with the current message for the stylesheet information that is stored in an element called ComIbmXslXmltStylesheetname.

        This node was available in a SupportPac for Version 2.1, and element ComIbmXslMqsiStylesheetname was used for the name of the style sheet, so the current node checks both elements. If both are present, the value in ComIbmXslXmltStylesheetname takes precedence.

      3. Broker Node Attribute Selection Priority, which has a default value of 3. The node uses the Stylesheet Name and Stylesheet Directory properties to determine the correct values.

      You can set more than one property to the same value, although if you do, the order of priority that is set by the node is the default order that is indicated above.

      If you set a value of ignore, the node does not search the corresponding location for the stylesheet identification. If you set all three properties to ignore, a runtime error is generated.

  4. On the Output Character Set tab, specify the order in which the node searches valid locations to find the character set to use for the output message. The highest priority setting is 1. The default order is:
    1. Message Environment Selection Priority, which has a default value of 1. The node searches the LocalEnvironment that is associated with the current message for the character set information that is stored in an element called ComIbmXslXmltOutputcharset; for example, to encode the output of the transformation as UTF-8, enter the value 1208 as a string in this element.

      This node was available in a SupportPac for Version 2.1, and element ComIbmXslMqsiOutputcharset was used for the output character set, so the current node checks both elements. If both are present, the value in ComIbmXslXmltOutputcharset takes precedence.

    2. Broker Node Attribute Selection Priority, which has a default value of 2. The node uses the property Output Character Set to determine the correct value.

      If you set a value for Output Character Set, the value that you enter must be numeric; for example, to encode the output of the transformation as UTF-16, enter 1200.

    You can set more than one property to the same value, although if you do, the order of priority that is set by the node is the default order that is indicated above.

    If you set a value of zero, the node does not search the corresponding location for the character set identification.

    If the node cannot determine the output character set from either of these two sources, either because no value is set or because the selection priorities are set to zero, the default value 1208 (UTF-8) is used. (The XSL specification indicates that the output character set can be specified in the style sheet; however, the XMLTransformation node ignores this value.)

  5. On the Detail Trace tab, set the trace setting to trace the actions of the XMLTransformation node. The default value for the Detail Trace property is Off. To activate trace, set the property to On.

    The trace information is written to a trace file XMLTTrace.log:

    • On z/OS systems, the file is located in install_dir/output, where install_dir is the directory in which you have installed the broker
    • On Windows systems, the file is located in <broker work path>\common\log.
    • On Linux and UNIX systems, the file is located in <broker work path>/common/log.

    If you set detailed trace on for one XMLTransformation node, it is on for all nodes in the execution group.

    This property is now deprecated. Any relevant trace now goes into the user trace, provided that user debug trace is enabled. The setting of Detail Trace in the XMLTransformation node does not affect any user trace.

  6. Stop and restart the execution group.
If you are dealing with large XML messages and receive an out of memory error, use the mqsireportproperties command to see the current value of the Java Heap size for the XSLT engine, and the mqsichangeproperties command to increase it:
mqsireportproperties brokerName -e executionGroupLabel 
                                 -o ComIbmJVMManager -n jvmMaxHeapSize
mqsichangeproperties brokerName -e executionGroupLabel 
                                 -o ComIbmJVMManager -n jvmMaxHeapSize -v newSize
replacing brokerName, executionGroupLabel, and newSize with the appropriate values.

The value that you choose for newSize depends on the amount of physical memory that your computer has, and how much you are using Java. A value in the range 512 MB (536870912) to 1 GB (1073741824) is typically sufficient.

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Terminals and properties

The XMLTransformation node terminals are described in the following table.

Terminal Description
In The input terminal that accepts the message for processing by the node.
Failure The output terminal to which the original message is routed if an error is detected during transformation.
Out The output terminal to which the successfully transformed message is routed.

The following tables describe the node properties. The column headed M indicates whether the property is mandatory (marked with an asterisk if you must enter a value when no default is defined); the column headed C indicates whether the property is configurable (you can change the value when you add the message flow to the bar file to deploy it).

The XMLTransformation node Description properties are described in the following table.

Property M C Default Description
Node name No No The node type The name of the node.
Short Description No No   A brief description of the node.
Long Description No No   Text that describes the purpose of the node in the message flow.

The XMLTransformation node Stylesheet properties are described in the following table.

Property M C Default Description
Stylesheet Name No Yes   The name of the style sheet, used if the stylesheet specification is searched for in node properties.

The XMLTransformation node Advanced properties are described in the following table.

Property M C Default Description
Stylesheet Directory No Yes   The path where the style sheet is located. This path is used by all location methods.
Stylesheet Cache Level No No 5 The number of compiled or parsed style sheets that are stored in this instance of the node.
XML Embedded Stylesheet Selection Priority Yes No 1 The priority value for searching for style sheet location information in the XML data.
Message Environment Selection Priority Yes No 2 The priority value for searching for style sheet location information in the LocalEnvironment folder of the current message.
Broker Node Attribute Selection Priority Yes No 3 The priority value for searching for style sheet location information as a property of the node

The XMLTransformation node Output Character Set properties are described in the following table.

Property M C Default Description
Output Character Set No No   The numeric value of the Output Character Set
Message Environment Selection Priority Yes No 1 The priority value for searching for the Output Character Set ID in the LocalEnvironment folder of the current message.
Broker Node Attribute Selection Priority Yes No 2 The priority value for searching for the Output Character Set ID as a property of the node.

The XMLTransformation node Detail Trace properties are described in the following table.

Property M C Default Description
Trace Setting Yes No Off This property controls whether tracing is on or off. If tracing is on, low level tracing is recorded in a file.
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