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Java Custom Function

Shared Configuration

The Java Custom Function resource allows you to create custom functions to use when mapping data in an activity’s input tab. These functions are also displayed when using the XPath Editor to build an XPath expression.

To create a custom function, you must write the function as a method of a Java class and compile the code into a Java class file. You then load that class file into the project using this resource.

When the class is loaded using this resource, TIBCO ActiveMatrix BusinessWorks inspects the contents of the class and only the class methods that meet the following restrictions are made available in XPath:

•	Only methods declared as public and static are loaded.

•	The input parameters and return values must be of one of the types described in Table 3.

•	The return value of the function cannot be void.

•	The method cannot be a constructor.

•	The method cannot explicitly throw an exception. Runtime exceptions are allowed, however.

•	Method names cannot be overloaded in a class or any imported classes in a single Java Custom Function resource. You can load methods of the same name into separate classes in separate Java Custom Function resources and use the Prefix field to differentiate between the methods.

•	If you make references to any imported class files, these classes must be available in the classpath configured for TIBCO ActiveMatrix BusinessWorks. The easiest way to make the imported classes available is to place them in the TIBCO/bw/2.0/lib directory.

•	Inner classes are not supported.

TIBCO ActiveMatrix BusinessWorks provides detailed online help for each XPath function. To provide online help for Java Custom Functions, create a two-dimensional array named HELP_STRINGS in your class. The element containing a string matching the function name is used as the help for that function. See Example Java Function for an example of creating the HELP_STRINGS array.

Table 3 Datatypes allows for Java custom functions

Type of Data	Datatypes Allowed for Input Parameters and Return Types
Strings and Characters	String	char
Boolean	Boolean	boolean
Numbers	int float double short long	Integer Float Double Short Long

 

Static variables are not supported in Java custom functions. Do not write custom functions that use static variables.

If there are different classes that have methods with the same names, the Prefix field allows you to specify a prefix for qualifying which method you want to use in an XPath function. See the description of the Prefix field below for more information.

See TIBCO ActiveMatrix BusinessWorks Process Design for more information about building XPath expressions and using the XPath editor.

Configuration

The Configuration tab has the following fields.

Field	Description
Name	The name to appear as the label for the resource.
Description	Short description of the shared resource. The method signature plus the description supplied in this field appear as the documentation of the function in the XPath editor. You can use simple HTML markup to format the text of this field, if you desire.
Suggested Prefix	A folder with the name you specify in this field appears in the Functions tab in the XPath editor. You can drag and drop methods from the loaded class into your XPath expression, just as you would with any standard XPath function. Use this name as a prefix for function names in this class, if multiple classes are loaded and function names are not unique among the classes. For example, if you have class1.method1 and class2.method1, you will need to specify class1 in the Suggested Prefix field when you load class1 into a Java Custom Resource. You would specify class2 in the Suggested Prefix field when loading class2. When using method1 in XPath expressions, you must qualify which method1 you are using by specifying class1:method1 or class2:method1 in the XPath expression. The value of this field must be unique across all loaded Java Custom Function resources, and the value must be a valid XPath identifier. Also, you cannot use global variables (that is, %variable%) in this field.
Class Location	The location of the class file you want to load. Use the Browse button to locate the class file. Note: This field is used to locate the file initially, but the file is actually loaded and stored in the repository. Once the file is loaded, it can be removed from its original location in the file system. If you want to change the file stored in the repository, you can use this field to reload a changed file or load a new file for this resource.
Class Data	The size of the class in bytes. Use the Load button after a class is selected in the Class Location field to load the class and determine its size.

Example Java Function

The following Java code implements custom Java functions. The example illustrates which methods of the class meet the restrictions and are therefore available as custom functions in XPath. The example also illustrates methods which do not meet the restrictions, and therefore are not available as custom functions.

 

package com.tibco;

 

public class Sample

{

      protected int mInternalValue;

 

      /**

      * The following method will not be available because it is

      * a constructor.

      */

      public Sample(int value)

      {

         mInternalValue = value;

      }

 

      /**

      * This method is used to concat two strings together. It

      * must be declared as public static to be made available in

      * TIBCO ActiveMatrix BusinessWorks.

      */

      public static String stringConcat(String s1, String s2)

      {

         return s1 + s2;

      }

 

      /**

      * This method is used to add two ints together. Note, that

      * it takes both an int type and an Integer object.

      */

      public static int intAdd(int lhs, Integer rhs)

      {

         return lhs + rhs.intValue();

      }

 

      /**

      * The following method will not be available because it

      * throws an exception.

      */

      public static int badAdd(int lhs, int rhs)

      throws Exception

      {

         long result = lhs + rhs;

         if (result > Integer.MAX_VALUE) {

            throw new ArithmeticException();

         }

      return new Long(result).intValue();

      }

 

      /**

      * The following method will not be availabe because it

      * returns nothing: its void.

      */

      public static void returnsNothing(String s)

      {

         System.out.println(s);

      }

 

      /**

      * The following method will not be available because it

      * is not static.

      */

      public int add(int rhs)

      {

         return mInternalValue + rhs;

      }

 

      /**

      * The following method will not be available becauses it

      * is not public.

      */

      protected static int protectedAdd(int lhs, int rhs)

      {

         return lhs + rhs;

      }

      /**

      * The following is a two-dimensional array that provides the

      * online help for functions in this class. Declare an array

      * named HELP_STRINGS.

      */

      public static final String[][] HELP_STRINGS ={

         {"stringConcat", "Joins two strings.",

         "Example", "stringConcat(\"test/testDict\",

         $input/key)"},

         {"intAdd", "Adds two integers.",

         "Example", "intAdd(5, $input/myInt)"},

}

 

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