You can launch the XPath Expression Builder from most property fields that support, or expect, XPath expressions as a value that can be entered into the field.
The use of the XPath Expression Builder is optional, in that it is an aid to you in developing message flow applications. The XPath Expression Builder helps you to construct message processing expressions in either XPath or ESQL. You are free to enter expressions by hand, or use the XPath Expression Builder to help construct such expressions.
The XPath Expression Builder does not support use of the $Body variable. You can use the $Body variable when you enter an expression by hand, but the XPath Expression Builder and associated validation in the IBM® Integration Toolkit do not support it. Use the $Root variable instead.
You can populate the fields, regardless of the state of the node; that is, whether the node is detached or connected, or fully, partially, or completely unconfigured.
Variables (or in ESQL terminology, correlation names) provide a list of all message tree start points that are applicable to the property field from which the dialog was launched.
If a field is a read-only or a read-write path field, expressions must start with such a variable to indicate which tree in which message assembly the path expression is mapping to.
XPath variable names map to existing correlation names found in ESQL field reference expressions, but to conform to the ESQL grammar they are designated as variable references by prefixing them with the dollar ($) character.
The XPath Expression Builder dialog box supports validation, which you can turn off on the XPath preferences page by clearing the Validate when creating XPath expressions check box.
If you select the $Root or $Body variables and create an expression that refers to the body of the message, the XPath expression contains the message element. This expression is correct for message bodies owned by the XMLNSC, XMLNS, XML, and DataObject domains.
For message bodies that are owned by the MRM, MIME, SOAP, and IDOC domains, you must remove the message element from the expression.
For example, the XPath expression $Body/my_message/my_field is correct for XMLNSC, but must be changed to $Body/my_field to be correct for MRM.
There are three main views when functions are supported.
If you expand Namespace settings in the XPath Expression Builder dialog you see a table of Prefix and Namespace pair strings. This table is automatically updated when XPath expressions are created. If the default prefix generated is not what you want, you can change it by clicking Change Prefix.
To add a prefix and namespace map entry click Add and complete the fields in the dialog.
To edit or delete an entry in the table, select the item and click Edit or Delete respectively.
Edit opens another field dialog allowing you to change the prefix and namespace.
For information about the preferences supplied with the XPath editor, see XPath editor preferences.