stevedlawrence commented on a change in pull request #394: URL: https://github.com/apache/incubator-daffodil/pull/394#discussion_r455763049
########## File path: daffodil-core/src/main/scala/org/apache/daffodil/dsom/walker/AbstractDSOMWalker.scala ########## @@ -0,0 +1,177 @@ +/* + * 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 + +/** + * Below is a series of "View" Mixins defined such that particular simple attributes + * of the core DSOM classes are exposed as a Walk is performed. + * + * Several of them have a walkDSOM method. By default, this method is called as the walk is performed, + * but a user implementing AbstractDSOMWalker can override this behavior by overriding walkFromRoot + * and implementing their own event handlers for each of the DSOM types. + */ + +trait CommonContextView { + def namespaces: scala.xml.NamespaceBinding +} + +trait TermView extends CommonContextView { + def isArray: Boolean + def isOptional: Boolean +} + +trait TypeView +trait SimpleTypeView extends TypeView { + def primType: PrimTypeView +} +trait ComplexTypeView extends TypeView { + def group: ModelGroupView +} + +trait ModelGroupView extends TermView { + def groupMembers: Seq[TermView] +} + +trait ChoiceView extends ModelGroupView +trait SequenceView extends ModelGroupView +trait GroupRefView extends ModelGroupView { + def isHidden: Boolean +} + +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 +} + +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. + */ +abstract class AbstractDSOMWalker { + + /** + * Method to be called on the beginning of the traversal. It is recommended to add some + * sort of wrapper element to a stack if you're doing a typical stack-based traversal. + * + * @param root the root element of the DFDL Schema + */ + protected def onWalkBegin(root: RootView): Unit + + /** + * Method to be called when the traversal concludes. It is recommended to put any post-processing + * and anything to tidy up the stack or the result here. + * + * @param root the root element of the DFDL Schema + */ + protected def onWalkEnd(root: RootView): Unit + + /** + * Method to be called whenever any element that is a Term is encountered. + * This applies to Sequence, Choice, GroupRef, ElementBase, etc. + * + * It is highly recommended that, when implementing this method, you pattern match + * some of these different sub-types at some point to handle each accordingly. + * + * @param termElement the term element + */ + def onTermBegin(termElement: TermView): Unit + + /** + * Method to be called when a Term element has finished processing + * + * @param termElement the term element + */ + def onTermEnd(termElement: TermView): Unit + + /** + * Method to be called when either a Simple or Complex Type element has been encountered. + * This is just the element for <simpleType> or <complexType>, so no implementation is necessary if you + * do not care about these wrapper portion; its children will be walked automatically. + * + * @param typeElement either a Simple or Complex type + */ + def onTypeBegin(typeElement: TypeView): Unit + + /** + * Method to be called when either a Simple or Complex Type element has been finished + * processing. See onTypeBegin method description + * + * @param typeElement either a Simple or Complex type + */ + def onTypeEnd(typeElement: TypeView): Unit + + /** + * Starts a DSOM walk from the Root object. By default, the walk is completed recursively in the helper + * method below, but a custom walk can be defined by overriding + * this method instead and calling local event handlers. + * @param schemaSetRoot The root element of the DFDL Schema. This will be the starting point of the traversal + */ + def walkFromRoot(schemaSetRoot: RootView): Unit = { + onWalkBegin(schemaSetRoot) + walkerHelper(schemaSetRoot) + // onWalkEnd will return the value returned by this method! Review comment: Can remove this comment now that walkerEnd doesn't return anything. ---------------------------------------------------------------- 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. 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