mbeckerle commented on a change in pull request #273: WIP: Add User Defined 
Functions Capability
URL: https://github.com/apache/incubator-daffodil/pull/273#discussion_r336186201
 
 

 ##########
 File path: 
daffodil-runtime1/src/main/scala/org/apache/daffodil/udf/UserDefinedFunctionService.scala
 ##########
 @@ -0,0 +1,185 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.daffodil.udf
+
+import collection.JavaConverters._
+import collection.mutable._;
+import java.util.ServiceLoader
+import java.util.ServiceConfigurationError
+import org.apache.daffodil.util.Misc
+import java.io.Serializable
+import org.apache.daffodil.util.LogLevel
+import org.apache.daffodil.util.Logging
+import java.lang.reflect.Method
+
+/**
+ * Loads all User Defined Function Providers on the classpath once and caches 
them in
+ * following look up tables that'll be used to look up the UDFs during Schema 
compile time.
+ *
+ * "$namespaceURI:$fName" -> classOf[UserDefinedFunction]
+ * "$namespaceURI:$fName" -> UserDefinedFunctionProvider
+ *
+ * It also does validation on the providers and classes and caches any warning 
and errors,
+ * which are then reported during compile time.
+ *
+ */
+object UserDefinedFunctionService extends Logging {
+  val evaluateMethodName = "evaluate"
+  type EvaluateMethod = Method
+  type ParameterTypes = Array[Class[_]]
+  type ReturnType = Class[_]
+  type UdfCallingInfo = (UserDefinedFunction, EvaluateMethod, ParameterTypes, 
ReturnType)
+  type NamespaceNameKey = String
+  private val functionClassesLookup: HashMap[NamespaceNameKey, Class[_]] = 
HashMap()
+  private val functionProviderLookup: HashMap[NamespaceNameKey, 
UserDefinedFunctionProvider] = HashMap()
+  private val InitializedUserDefinedFunctionsCache: HashMap[NamespaceNameKey, 
Option[UdfCallingInfo]] = HashMap()
+  lazy val classUserDefinedFunctionInfo = classOf[UserDefinedFunctionInfo]
+  lazy val classUserDefinedFunction = classOf[UserDefinedFunction]
+  lazy val classJSerializable = classOf[java.io.Serializable]
+  lazy val currentClassPath = Misc.classPath.map(_.toString).mkString("\n")
+
+  val loader: ServiceLoader[UserDefinedFunctionProvider] = 
ServiceLoader.load(classOf[UserDefinedFunctionProvider])
+
+  loader.asScala.map { provider =>
+    val providerfc = provider.getUserDefinedFunctionClasses
+    lazy val providerClassName = provider.getClass.getName
+
+    if (providerfc == null || providerfc.isEmpty) {
+      val wstr = s"User Defined Function Provider ignored: 
${providerClassName}. No User Defined Functions found."
+      log(LogLevel.Warning, wstr)
+    } else {
+      val missingAnnotations = 
providerfc.filterNot(_.isAnnotationPresent(classUserDefinedFunctionInfo))
+      val nonUserDefinedFunction = 
providerfc.filterNot(classUserDefinedFunction.isAssignableFrom(_))
+
+      if (!missingAnnotations.isEmpty) {
+        val wstr = s"User Defined Function Provider ignored: 
${providerClassName}. Below must be annotated with 
${classUserDefinedFunctionInfo.getName}" +
+          s"\n${missingAnnotations.map(_.getName).mkString("\t", "\n\t", "")}"
+        log(LogLevel.Warning, wstr)
+      }
+
+      if (!nonUserDefinedFunction.isEmpty) {
+        val wstr = s"User Defined Function Provider ignored: 
${providerClassName}. Below must implement ${classUserDefinedFunction.getName}" 
+
+          s"\n${nonUserDefinedFunction.map(_.getName).mkString("\t", "\n\t", 
"")}"
+        log(LogLevel.Warning, wstr)
+      }
+
+      if (missingAnnotations.isEmpty && nonUserDefinedFunction.isEmpty) {
+        providerfc.map { fc =>
+          val fcClassName = fc.getName
+          val fInfo = fc.getDeclaredAnnotation(classUserDefinedFunctionInfo)
+          val fns = fInfo.namespaceURI()
+          val fname = fInfo.name()
+          if (List(fns, fname).exists { p => Option(p).isEmpty || 
p.trim.isEmpty }) {
+            val wstr = s"User Defined Function ignored: ${fcClassName} from 
provider ${providerClassName}." +
+              (if (Option(fns).isEmpty || fns.trim.isEmpty) " Annotation 
namespace field is empty or invalid." else "") +
+              (if (Option(fname).isEmpty || fname.trim.isEmpty) " Annotation 
namespace field is empty or invalid." else "")
+            log(LogLevel.Warning, wstr)
+          }
+          val key = s"$fns:$fname"
+          if (functionProviderLookup.contains(key)) {
+            val estr = s"User Defined Function ignored: ${fcClassName} from 
provider ${providerClassName}. Duplicate $key found."
+            log(LogLevel.Error, estr)
 
 Review comment:
   Are we talking about detecting duplicate UDFs in different service provider 
jars on the classpath?
   
   My usual experience of classpath loading is that it is order sensitive, and 
you are explicitly allowed to have the same thing defined more than once. The 
first one in classpath order "wins", and this is an intentional way users can 
do partial overriding of functionality by inserting a new jar ahead on the 
classpath. 
   
   So if two service providers jars are on the classpath and both provide UDFs 
and they provide the same UDF definition, then I think the first should "win" 
and the second and beyond should be ignored, probably silently since it can be 
an expected ordinary configuration that has this sort of classpath overriding 
going on. I.e., it's not necessarily anything to warn about.  
   

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