org.apache.daffodil.udf

Class UserDefinedFunctionProvider

java.lang.Object

org.apache.daffodil.udf.UserDefinedFunctionProvider

public abstract class UserDefinedFunctionProvider
extends java.lang.Object

Abstract class used by ServiceLoader to poll for UDF providers on classpath.

Through this class, several User Defined Functions can be made available to Daffodil via a single entry in the META-INF/services file.

UDF Providers must subclass this, and must initialize the userDefinedFunctionClasses array with all the UDF classes it is providing.

If the UDFs being provided have constructors with arguments, the provider subclass must also implement the createUserDefinedFunction to return an initialized function class object based on the supplied namespace and name.

Subclasses must also supply a src/META-INF/services/org.apache.daffodil.udf.UserDefinedFunctionProvider file in their JAVA project in order to be discoverable by Daffodil.

Constructor Summary

Constructors

Constructor and Description
UserDefinedFunctionProvider()

Method Summary

Modifier and Type	Method and Description
UserDefinedFunction	createUserDefinedFunction(java.lang.String namespaceURI, java.lang.String fName) Finds and initializes User Defined Function class based on namespace and name provided.
abstract java.lang.Class<?>[]	getUserDefinedFunctionClasses() Must be implemented to return the classes of the User Defined Function this provider is aware of/providing

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UserDefinedFunctionProvider

public UserDefinedFunctionProvider()

Method Detail

getUserDefinedFunctionClasses

public abstract java.lang.Class<?>[] getUserDefinedFunctionClasses()

Must be implemented to return the classes of the User Defined Function this provider is aware of/providing

Returns:

array of the different UserDefinedFunction classes it provides

createUserDefinedFunction

public UserDefinedFunction createUserDefinedFunction(java.lang.String namespaceURI,
                                                     java.lang.String fName)
                                              throws java.lang.IllegalArgumentException,
                                                     java.lang.SecurityException,
                                                     java.lang.ExceptionInInitializerError,
                                                     java.lang.ReflectiveOperationException

Finds and initializes User Defined Function class based on namespace and name provided. The UserDefinedFunctionIdentification annotation applied to the function class must match name and namespaceURI field passed in from the schema. Must be overloaded if the function class's constructor takes arguments. Otherwise it will throw exceptions.

Parameters:

namespaceURI - XML namespace associated with schema function call

fName - function name called in schema

Returns:

initialized UserDefinedFunction object that must contain evaluate function with desired functionality

Throws:

java.lang.SecurityException - if security manager exists and disallows access

java.lang.IllegalArgumentException - if the UDF doesn't have a no-argument constructor

java.lang.ExceptionInInitializerError - if there is an issue initializing the UDF object

java.lang.ReflectiveOperationException - if the UDF doesn't have a no-argument constructor or if there is an issue initializing the UDF object