[GitHub] [incubator-daffodil] mbeckerle commented on a change in pull request #279: WIP: User Defined Functions feature

[GitBox <gi...@apache.org>]

mbeckerle commented on a change in pull request #279: WIP: User Defined Functions feature
URL: https://github.com/apache/incubator-daffodil/pull/279#discussion_r338657424
 
 

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 File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/udf/UserDefinedFunctionService.scala
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+/*
+ * 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 org.apache.daffodil.util.LogLevel
+import org.apache.daffodil.util.Logging
+import java.lang.reflect.Method
+import org.apache.daffodil.dpath.NodeInfo
+import java.io.ObjectOutputStream
+import java.io.Serializable
+import java.io.ObjectInputStream
+
+/**
+ * Loads, validates and caches (for use at schema compile time) all User Defined Functions
+ * and their Providers from the classpath.
+ *
+ */
+object UserDefinedFunctionService extends Logging {
+  lazy val evaluateMethodName = "evaluate"
+
+  /**
+   * Class to make the evaluate Method serializable and to optimize our reflection lookups
+   * to happen once (per call) during deserialization, rather than at evaluation time.
+   */
+  case class UserDefinedFunctionMethod(
+      val decClass: Class[_],
+      val methodName: String,
+      val paramTypes: Array[Class[_]])
+      extends Serializable {
+
+    @transient lazy val method: Method = {
+      lookupMethod
+    }
+
+    def lookupMethod() = {
+     val m = decClass.getMethod(methodName, paramTypes: _*)
+     m
+    }
+
+    @throws(classOf[java.io.IOException])
+    private def writeObject(out: ObjectOutputStream) : Unit = {
+      out.defaultWriteObject()
+    }
+
+    @throws(classOf[java.io.IOException])
+    @throws(classOf[java.lang.ClassNotFoundException])
+    private def readObject(in: ObjectInputStream): Unit = {
+      in.defaultReadObject()
+      this.method
+    }
+  }
 
 Review comment:
   I think the right behavior should be only UDFs that are used by the schema should get looked up. I should be able to have some older, stale/broken UDF on the classpath, so long as I don't use it it shouldn't bother me. Make sense?
   
   In general, object construction time should never do anything that can possibly fail/throw an exception. Otherwise when it fails, well the object itself isn't even fully constructed and that can make it hard to figure out what is going on.  ( This is one of the reasons scala lazy val is so useful just for ordinary object-oriented programming. )

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