Mapping an element by using a Custom Java transform
In the Graphical
Data Mapping editor,
you can use a method in a Java™ class
to set the value of an output element. You can use the Custom Java transform to invoke a Java method, optionally passing
one or more values to its parameters.
Procedure
Complete the following steps to use Java in a Custom Java transform:
- Create a message map.
When you use Java code
in a map, you can define the map in a static library project, a shared
library project, an application project, or an integration project.
You can define the Java code
in one or more Java projects.
Your map project must reference these Java projects.
For more information, see
Adding
a project to an application, integration service, or library.
Note: When
the map uses Java code available
in a shared library, you must create the map in the shared library
project where the Java code
is available.
For more
information, see Creating a message map.
- Add a Custom Java transform
to the map.
- If you have already defined a Java class,
select the class in the General tab of the Properties page
of the transform or, if you have not defined a Java class, complete the following steps to
define the required Java class:
- In the General tab of the Properties page
of the transform, click New.
- Select one of the following options, and complete the
associated steps:
- Create a new Java project
to store the class:
- Select Create the class in a new Java project to be
created and click Next.
- Complete the fields in the dialog (for
more information, see Creating
a Java project) and
click Next.
- Use an existing Java project
to store the class:
- Select Create the class in one of the existing Java
projects.
- Select the Java project
from the list and click Next.
The New Java class wizard is
displayed.
- Complete the New Java class wizard. At a minimum, complete the following fields:
- In the Source field, select the src folder
of your Java project.
- In the Package field, enter the name of
a package to contain the new class.
- In the Name field, enter a name for the
class.
- Click Finish. If prompted, click Yes to
create a reference from the application that contains your map to
your Java project. The Java class is
created with a sample method.
- In the General tab of the Properties page
of the transform, click Edit to complete your Java class.
The Java class that you provide to the
map must have static methods that return the appropriate type for
the value of the output element, and take parameters of the appropriate
type for the wired inputs.
You can use the MbElement class
in a Java method to pass a complex
type, a wildcard xsd:any, or a wildcard xsd:anySimpleType.
For more information, see Custom Java.
For
example, the following Java method
might be used in a Custom Java transform
that has three input elements, of types a xs:string, xs:decimal,
and xs:boolean and the output element is a xs:decimal:
public static BigDecimal calSomething(String memType, BigDecimal stdCost, boolean flag) {
BigDecimal actualCost = stdCost;
if (flag & memType.startsWith("gold")) {
BigDecimal discRate = new BigDecimal(0.9);
actualCost = actualCost.multiply(discRate);
}
return actualCost;
}
Note: If the input element that is used to
provide a value for a Java method
is not of the correct type, you can use a type cast function, for
example
xs:int( $var ), to set the required
type. For more information, see
Cast type (xs:type).
- Configure the method that defines the transformation logic
that is applied by the Custom Java transform. In the
General tab of the Properties page
of the transform, complete the following steps:
- Click Browse and complete the
following steps:
- In the Select Type window, enter the name
of the Java package in the Select
entries field. The package must contain the Java class.
Note: You must start typing the
name of your Java package before
you can see any classes to choose from in the Select entries field.
- Select a Java class and
click OK.
Note: If the Java project
that contains the Java class
does not build in Eclipse, then the Java class
is not visible anywhere in the map. You must resolve all the Java errors before you can configure
the class and method in the General tab of
the Properties page. You can see the errors in
the Problems tab.
- Configure one Java method.
You access the methods that are available through the drop-down.
If the method has parameters, they are added automatically
in the Parameters section of the General tab.
- Set the value of each parameter. Complete the following
steps to set the value of a parameter:
- Select a parameter.
- Click the Value column of a parameter.
- Select an element, or select the option Edit custom
XPath expression parameter. If you select the
edit option, you can define an XPath expression or a call
to a static method on an imported Java class that is visible to the map. You can also create a complex expression
that includes XPath, Java, and
extension functions such as iib:getUserDefinedProperty("propertyname").
When you define a Java method
and a Java class in the General tab
of the Properties page of a Custom
Java transform, an import is automatically added
in the map to refer to the package qualified Java class. A prefix based on the class
name is added. All the public static methods in
this Java class are then available
in content-assist when building expressions in other transforms.
Alternatively,
you can use Java class methods
that use standard Java types
in any expression within your map, for example as part of the
condition of an if transform. Before you can
use Java methods in expressions,
import the Java class into the
map. The method is then available in content assist (Ctrl-space).
To import a Java class into a map, configure the Java
imports tab in the Properties page
of the map.
What to do next
Deploy and test the message map. For more information, see Troubleshooting a message map.