mbeckerle commented on a change in pull request #651: URL: https://github.com/apache/daffodil/pull/651#discussion_r723515874
########## File path: daffodil-core/src/main/scala/org/apache/daffodil/layers/LayerCompilerRegistry.scala ########## @@ -0,0 +1,72 @@ +/* + * 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.layers + + +import org.apache.daffodil.exceptions.ThrowsSDE + +import scala.collection.mutable + +/** + * Transformers have factories. This lets you find the transformer factory + * by the name obtained from dfdlx:layerTransform. + */ +object LayerCompilerRegistry { + + private lazy val layerCompilerMap = new mutable.HashMap[String, LayerCompiler] + + def register(layerCompiler: LayerCompiler): Unit = { + layerCompilerMap.put(layerCompiler.name, layerCompiler) + } + /** + * Given name, finds the factory for the transformer. SDE otherwise. + * + * The state is passed in order to provide diagnostic context if not found. + */ + def find(name: String, context: ThrowsSDE): LayerCompiler = { + val maybeCompiler: Option[LayerCompiler] = layerCompilerMap.get(name) + if (maybeCompiler.isEmpty) { + // + // TODO: Daffodil-1927 + // This is where we would try to dynamically load a layer transform compiler + // for the given layer name. + // + val choices = layerCompilerMap.keySet.mkString(", ") + context.SDE("The dfdlx:layerTransform '%s' was not found. Available choices are: %s", name, choices) + } else { + maybeCompiler.get + } + } Review comment: Given the fact that we don't have a Java API defined here, perhaps we can split this task of making pluggable layers into two. The first is what I've done so far which is to modularize the layers, enabling them to be easily added. But you must do so in scala, and are probably adding them in the daffodil-runtime1-layers module if they're to be come part of Daffodil. If you are building your own proprietary layer transforms, then you would build them in scala much the same way ,but you would put them in a Jar, and you would be responsible to get code executed which registers them, by just calling LayerCompilerRegistry.register(....). The second task would be to define an external Java-based API and true dynamic loading capability. Given the above, I think this aspect would be far lower priority. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
