| /* |
| * 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.iceberg.common; |
| |
| import java.util.LinkedHashSet; |
| import java.util.Set; |
| import org.apache.iceberg.relocated.com.google.common.base.Joiner; |
| |
| public class DynClasses { |
| |
| private DynClasses() { |
| } |
| |
| public static Builder builder() { |
| return new Builder(); |
| } |
| |
| public static class Builder { |
| private ClassLoader loader = Thread.currentThread().getContextClassLoader(); |
| private Class<?> foundClass = null; |
| private boolean nullOk = false; |
| private Set<String> classNames = new LinkedHashSet<>(); |
| |
| /** |
| * Set the {@link ClassLoader} used to lookup classes by name. |
| * <p> |
| * If not set, the current thread's ClassLoader is used. |
| * |
| * @param newLoader a ClassLoader |
| * @return this Builder for method chaining |
| */ |
| public Builder loader(ClassLoader newLoader) { |
| this.loader = newLoader; |
| return this; |
| } |
| |
| /** |
| * Checks for an implementation of the class by name. |
| * |
| * @param className name of a class |
| * @return this Builder for method chaining |
| */ |
| public Builder impl(String className) { |
| classNames.add(className); |
| |
| if (foundClass != null) { |
| return this; |
| } |
| |
| try { |
| this.foundClass = Class.forName(className, true, loader); |
| } catch (ClassNotFoundException e) { |
| // not the right implementation |
| } |
| |
| return this; |
| } |
| |
| /** |
| * Instructs this builder to return null if no class is found, rather than |
| * throwing an Exception. |
| * |
| * @return this Builder for method chaining |
| */ |
| public Builder orNull() { |
| this.nullOk = true; |
| return this; |
| } |
| |
| /** |
| * Returns the first implementation or throws ClassNotFoundException if |
| * one was not found. |
| * |
| * @param <S> Java superclass |
| * @return a {@link Class} for the first implementation found |
| * @throws ClassNotFoundException if no implementation was found |
| */ |
| @SuppressWarnings("unchecked") |
| public <S> Class<? extends S> buildChecked() throws ClassNotFoundException { |
| if (!nullOk && foundClass == null) { |
| throw new ClassNotFoundException("Cannot find class; alternatives: " + |
| Joiner.on(", ").join(classNames)); |
| } |
| return (Class<? extends S>) foundClass; |
| } |
| |
| /** |
| * Returns the first implementation or throws RuntimeException if one was |
| * not found. |
| * |
| * @param <S> Java superclass |
| * @return a {@link Class} for the first implementation found |
| * @throws RuntimeException if no implementation was found |
| */ |
| @SuppressWarnings("unchecked") |
| public <S> Class<? extends S> build() { |
| if (!nullOk && foundClass == null) { |
| throw new RuntimeException("Cannot find class; alternatives: " + |
| Joiner.on(", ").join(classNames)); |
| } |
| return (Class<? extends S>) foundClass; |
| } |
| } |
| } |