stevedlawrence commented on a change in pull request #394: URL: https://github.com/apache/incubator-daffodil/pull/394#discussion_r453863360
########## File path: daffodil-core/src/main/scala/org/apache/daffodil/dsom/walker/AbstractDSOMWalker.scala ########## @@ -0,0 +1,163 @@ +/* + * 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.dsom.walker + +import org.apache.daffodil.dpath.NodeInfo.PrimType + +trait CommonContextView { + def namespaces: scala.xml.NamespaceBinding +} + +trait TermView extends CommonContextView { + def isArray: Boolean + def isOptional: Boolean + def walkDSOM[T](walker: AbstractDSOMWalker[T]): Unit = { + walker.onTermBegin(this) + walker.onTermEnd(this) + } +} + +trait SimpleTypeView { + def primType: PrimType +} +trait ComplexTypeView { + def group: ModelGroupView +} + +trait ModelGroupView extends TermView { + def groupMembers: Seq[TermView] + override def walkDSOM[T](walker: AbstractDSOMWalker[T]): Unit = { + walker.onTermBegin(this) + this.groupMembers.foreach(_.walkDSOM(walker)) + walker.onTermEnd(this) + } +} + +trait ChoiceView extends ModelGroupView +trait SequenceView extends ModelGroupView +trait GroupRefView extends ModelGroupView { + def isHidden: Boolean + override def walkDSOM[T](walker: AbstractDSOMWalker[T]): Unit = if (!isHidden) super.walkDSOM(walker) +} + +trait ElementDeclView extends CommonContextView { + def isSimpleType: Boolean + def isComplexType: Boolean + def simpleType: SimpleTypeView + def complexType: ComplexTypeView + def hasDefaultValue: Boolean +} + +trait ElementBaseView extends ElementDeclView with TermView { + def name: String + override def walkDSOM[T](walker: AbstractDSOMWalker[T]): Unit = { + walker.onTermBegin(this) + if (isComplexType) { + walker.onTypeBegin(Right(complexType)) + complexType.group.walkDSOM(walker) + walker.onTypeBegin(Right(complexType)) + } else { + walker.onTypeBegin(Left(simpleType)) + walker.onTypeBegin(Left(simpleType)) + } + walker.onTermEnd(this) + } + +} + +trait RootView extends ElementBaseView + +/** + * A class designed to walk the internal representation of a DFDL Schema File. + * + * There are 2 main event handlers an implementing class has to worry about: one for Terms, and + * another for Types. These are called as the DSOM is walked. + * + * Though recursion is used here to define the walk, it is not advised to use recursion between + * these event handlers. Instead, consider a stack-like structure, as the DFDL Schema structure + * as well as the recursive method call structure can be represented by trees. + * @tparam T the return type of walkDSOMSchema and onWalkEnd. This should be a class used to + * represent the structure of the Schema. You could always make it Unit if you don't + * want these methods to return anything. + */ +abstract class AbstractDSOMWalker[T] { + + /** Review comment: One concern with requireing scala is building a nar for a NiFi controller/processer uses a maven archetype template to build the project structure. If the API requires Scala, building such a nar might be problematic, or at least this generated maven project needs to be modified support scala compilation. I assume that's possible, but I'm not sure. Other integrations might have similar issues. And if the the utltimate goal is to upstream this into NiFi tree, it almost certainly needs to be Java friendly--as far as I know, NiFi doesn't have any Scala code in their source tree. It we decide to only support scala (which doesn't seem unreasonable), and if there's a potential for changes to support Java, I would at least recomend we say that this API is experiemental and subject to change so that we don't have to worry as much about backwards compatibility and can more easily make such changes. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
