stevedlawrence commented on a change in pull request #431: URL: https://github.com/apache/incubator-daffodil/pull/431#discussion_r504962241
########## File path: daffodil-lib/src/main/scala/org/apache/daffodil/util/Validators.scala ########## @@ -0,0 +1,71 @@ +/* + * 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.util + +import java.util.ServiceLoader + +import org.apache.daffodil.api.CompiledValidator +import org.apache.daffodil.api.Validator +import org.apache.daffodil.api.Validator.CompilerOps.CheckArgs +import org.apache.daffodil.api.ValidatorNotFoundException + +import scala.collection.JavaConverters._ + +object Validators { + val default: Validator = new DefaultValidatorSPIProvider + def compiler(): ValidatorCompiler = new Compiler + + trait ValidatorCompiler { + def find(name: String): Option[CompiledValidator] + def isRegistered(name: String): Boolean + def compile(name: String, args: Validator.ArgumentList): CompiledValidator + } + + private class Compiler extends ValidatorCompiler { + private var compiled = Map.empty[String, CompiledValidator] + private lazy val impls: Map[String, Validator] = + ServiceLoader + .load(classOf[Validator]) + .iterator() + .asScala + .map(v => v.name() -> v) + .toMap + Review comment: Can you describe the motivation for using a ServiceLoader for providing validators rather than just providing an API where a user can provide validators (that follow the Validator API, and meeting requirements like thread safe and Serializable)? I feel like SPI things are useful when you just want to swap different mechanisms without any code/configuration changes, but it seems like that's not really the case here. Swapping different validation mechanisms requires speciying the validation name somewhere (I think) and somehow providing args, so swapping in a new validation mechamisnm still requires code 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: [email protected]
