This chapter discusses how to implement a function in Java as a Java XPath Class, deploy an XPath/XSL function in JDeveloper and deploy an XPath/XSL function in application servers.
This chapter includes the following sections:
Section 11.1, "Implementing a Function in Java as a Java XPath Class"
Section 11.2, "Deploying the XPath/XSL Function in JDeveloper"
Section 11.3, "Deploying the XPath/XSL Function in the Application Server"
Since the custom function can be invoked either as an XPath or XSL function, the implementation class must take care of both. For this reason, the hosting class must have at least:
A public static method with the same name as the function name.
This method is used by the XSL function invocation. Currently, optional parameters on custom functions are not supported when registering with JDeveloper. For this reason, it is recommended to avoid functions with optional parameters.
A public static inner class which implements oracle.fabric.common.xml.xpath.IXPathFunction
This interface has the method:
Object call (IXPathContext context, List args) throws XPathFunctionException that gets called by service engines when the XPath function is invoked. When the function is called, the runtime engine passes the XPathContext and list of arguments passed to the function. IXPathContext enables you to get access to the BPEL variable values within the execution context. The implementation of this method should naturally delegate to the public static method representing the function.
Example 11-1 illustrates a custom function implementation to get the current date. The implementation takes care of supporting both XSL and XPath. The function also has an optional parameter to show how overloaded methods are implemented:
Example 11-1 Custom Function Implementation to Get the Current Date
package oracle.apps.aia.core;•
import java.text.SimpleDateFormat;
import java.util.Date; import
java.util.List;
import oracle.fabric.common.xml.xpath.IXPathContext;
import oracle.fabric.common.xml.xpath.IXPathFunction;
import oracle.fabric.common.xml.xpath.XPathFunctionException;
public class DateUtils
{
public static class GetCurrentDateFunction implements IXPathFunction
{
public Object call(IXPathContext context, List args)
throws XPathFunctionException
{
if (args.size() == 1)
{
String mask = (String) args.get(0);
if(mask==null || mask.equals(""))
mask = "yyyy-MM-dd";
return getCurrentDate(mask);
}
throw new XPathFunctionException("must pass one argument.");
}
}
public static String getCurrentDate(String formatMask)
{
SimpleDateFormat df = new SimpleDateFormat(formatMask)
String s = df. format (new Date());
return s;
}
. . .
}
These naming standards are enforced:
Function name
Function implementation class
Function implementation method
Function inner class
Function namespace
Function namespace prefix
The function name must follow the standard Java method naming standards where the name should be Lower-Camel-Case.
Example: getCurrentDate, getEBMHeaderValue, ...
You can have one or more function implemented in the same class. The class name must follow the Java class naming standard where it should be Upper-Camel-Case and convey the functionality of the functions it implements.
Example: EBMHeaderUtils, RoutingUtils, ...
The implementation class will have a method for each XPath function. The method should be named the same as the function name. The parameter's data types should match the function parameter data types. If there are optional parameters in the function, you should have a different overloaded method to handle the extra optional parameters.
Example: getCurrentDate, getEBMHeaderValue, ...
There should be an inner-class for each XPath function named exactly as the Upper-Camel-Case of the function with a 'Function' suffix. The inner class is only needed to access the XPath function from BPEL. The inner class will have to implement the com.oracle.bpel.xml.XPath.IXPathFunction interface.
Example: GetESBHeaderValueFunction, ...
For the function to appear in both the BPEL expression builder wizard and the XSL Mapper, the namespace must start with: http://www.oracle.com/XSL/Transform/java/ then followed by the fully qualified name of the Java class, which implements the function.
Example:
http://www.oracle.com/XSL/Transform/java/oracle.apps.aia.core.ebmheader.EBMHeaderUtils
http://www.oracle.com/XSL/Transform/java/oracle.apps.aia.order.route.RoutingUtils
The XPath 1.0 and XSL 1.0 data types are supported as return or input parameters to the function, as shown in Table 11-1:
Custom functions should be registered in JDeveloper to be able to show them with BPEL expression builder and in the XSL Mapper. To do that, provide a User Defined Extension Functions config file [ext-soa-xpath-functions-config.xml], as shown in Example 11-2, and register it with JDeveloper through FilePreferencesXSL Map.
Example 11-2 User Defined Extension Functions Config File
<?xml version="1.0" encoding="UTF-8"?> <soa-xpath-functions xmlns=http://xmlns.oracle.com/soa/config/xpath xmlns:utl="http://www.oracle.com/XSL/Transform/java/oracle.apps.aia.core.DateUtils" <function name="utl:getCurrentDate"> <className>oracle.xpath.CustomFunction</className> <return type="string"/> <params> <param name="formatMask" type="string"/> <params> </function> <function ...> . . . </function> </functions>
The implementation classes must be zipped/jared and dropped at:. $SOA_HOME/soa/modules/oracle.soa.ext_11.x.x/classes folder. This way, these classes will be placed in the classpath of WebLogic server.
The Java XPath function should be registered with the application server. This is done by adding an entry in the ext-soa-xpath-functions-config.xml file, which is found at: $SOA_HOME/soa/modules/oracle.soa.ext_11.x.x/classes\META-INF. This file contains the list and descriptions of all XPath functions defined in the system.
Each function entry in this file has this information:
<function>: Has the name attribute that defines XPath function name.
<classname>: Defines the XPath implementation class name. In this case, it is the inner class name.
<return>: Used to define return type.
<params>:
All the parameters required by the function.
<param name="formatMask" type="string"/>
For each of the parameter passed specify the name and the data type of the input.
<function name="utl:getCurrentDate"> <className>oracle.xpath.CustomFunction</className> <return type="string"/> <params> <param name="formatMask" type="string"/> <params> </function>
The implementation classes must be dropped at: $SOA_HOME/soa/modules/oracle.soa.ext_11.x.x/classes folder. This way, these classes will be placed in the classpath of the SOA container and available to the classloader.