Transforms (Mapping operations)

In the Graphical Data Mapping editor, you can define mapping operations such as transforms, cast functions, or XPath 2.0 functions. Mapping operations define the transformation actions on input data, and set the result to the output element.

Mapping operations to transform graphically your data

You can use any of the following transforms to map graphically your data in the Graphical Data Mapping editor:

Core mapping transforms: You can use built-in structural and functional mapping operations to graphically construct the required message transformations to build the output message. For more information, see Transform types in the Graphical Data Mapping editor.
Custom transforms: You can define specialized transformations to build custom ESQL functions, XPath 2.0, or Java™. For more information, see Transform types in the Graphical Data Mapping editor.
XPath functions: You can use XPath 1.0 and XPath 2.0 functions to transform data in a message map. You can also build compound XPath expressions by using the Custom XPath transform; see Custom XPath.
All XPath 2.0 functions are supported in the form fn:functionName.

For more information about XPath, see the online document W3C XML Path Language (XPath) 2.0.
IBM Integration Bus mapping functions. You can use a set of IBM® Integration Bus mapping functions (iib:functionName), for example, to access a user-defined property value. For more information, see Custom XPath.
Database transforms:
- You can use the Select transform to query one or more database tables, and retrieve data. You can use the data in the message map to set output element values, define conditions, or use as input to build other transforms conditions. Database tables can be set as extra outputs of a message map. For more information, see Selecting data from a table.
- You can use a database routine transform to call a stored procedure from a database, and retrieve data. You can use the data in the message map to set output element values, define conditions, or use as input to build other transforms conditions.
  Note: For information on the support for stored procedures, see Support for stored procedures.
Cache transforms: By using Cache transforms you can interact with data that is stored in a global cache. For more information, see Accessing a global cache by using a Mapping node.
You can use the following transforms:
- Cache Put transform: You use the Cache Put transform to add a key-value pair into the global cache. For more information, see Adding key-value pairs to the global cache by using a Mapping node.
- Cache Get transform: You use the Cache Get transform to retrieve a value from the global cache by providing the associated key. For more information, see Retrieving a value from the global cache by using a Mapping node.
- Cache Remove transform: You use the Cache Remove transform to remove a key-value pair from the global cache. For more information, see Removing a key-value pair from the global cache by using a Mapping node.

Mapping operations to modify data in a database

Database tables can be set as more outputs of a message map.

You can use any of the following transforms to modify data in a database:

Insert transform: You use the Insert transform to add one new row of data, or multiple rows of data, into a database table. For more information, see Inserting data into a table.
Update transform: You use the Update transform to modify a row of data, or multiple rows of data, in a database table. For more information, see Updating data in a table.
Delete transform: You use the Delete transform to delete a row of data, or multiple rows of data, in a database table. For more information, see Deleting data from a table.
Database routine transform: You use a database routine transform to call a stored procedure or user-defined function from a database to insert, delete, or update data in one database table. For more information, see Calling a stored procedure from a map.

At design time, you must have a database definition file (.dbm file) in an available Data Design project for each database that you want to access. A data definition file contains one connection per database system.

At run time, you must have a JDBC connection of Type 4 defined for each database that your message map uses. You must configure a JDBCProvider configurable service per database. The JDBCProvider service name for a runtime database must be the same name as the development database name that you use in your message map.

For more information, see Modifying data in a database by using mapping.

Cast function to define a schema type

In the Graphical Data Mapping editor, you can use the Cast function to cast schema types.

You must cast a schema in any of the following instances:

Cast the value that you assign to an output element so it matches the output element schema definition type.
Cast the value of an element that you use as a parameter to a function where the parameter is of a different type.
Cast the value of an element that you use as a condition on a transform where the type is different.
Cast the value of an element when you work with a database, and the types differ.

To cast a schema, you can use the xs:castOperation functions, where castOperation is the name of the cast function.

Mapping behavior driven by the type of operation

When the transformations in the message map are constructed, the values for output message elements can be derived from any of the following components:

Input message elements, through any of the following mapping operations:
- Move, Convert, and other built-in transforms in the Graphical Data Mapping editor.
- XPath 2.0 functions (prefix fn:). All XPath 2.0 functions are supported by the Mapping node. For more information about XPath, see W3C XML Path Language (XPath) 2.0.
- Database input by using a database Select transform.
- Schema type casts. For more information, see Mapping xsd:any on an input or output message.
Extra functions, which allow multiple input values to produce the output value, such as concat and join.
The result of database Select, Insert, Update, Delete, and Database routine transforms.
Constant values, through an Assign operation that uses a supplied value.
Custom functions, user-defined XPath, Java, or ESQL.

The logic to derive values can be simple or complex. In addition to the transformation operations that set an output value, structural transforms are provided to enable conditional statements, loops, and nesting of transform logic into local maps.

For information about the supported transform types, see Transform types in the Graphical Data Mapping editor.