| /* |
| * 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.beam.sdk.coders; |
| |
| import static org.apache.beam.vendor.guava.v20_0.com.google.common.base.Preconditions.checkArgument; |
| |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| import java.util.Arrays; |
| import java.util.List; |
| import org.apache.beam.sdk.values.TypeDescriptor; |
| import org.apache.beam.vendor.guava.v20_0.com.google.common.base.MoreObjects; |
| |
| /** Static utility methods for creating and working with {@link CoderProvider}s. */ |
| public final class CoderProviders { |
| private CoderProviders() {} // Static utility class |
| |
| /** |
| * Creates a {@link CoderProvider} from a class's {@code static <T> Coder<T> of(TypeDescriptor<T>, |
| * List<Coder<?>>}) method. |
| */ |
| public static CoderProvider fromStaticMethods(Class<?> rawType, Class<?> coderClazz) { |
| checkArgument( |
| Coder.class.isAssignableFrom(coderClazz), |
| "%s is not a subtype of %s", |
| coderClazz.getName(), |
| Coder.class.getSimpleName()); |
| return new CoderProviderFromStaticMethods(rawType, coderClazz); |
| } |
| |
| /** Creates a {@link CoderProvider} that always returns the given coder for the specified type. */ |
| public static CoderProvider forCoder(TypeDescriptor<?> type, Coder<?> coder) { |
| return new CoderProviderForCoder(type, coder); |
| } |
| |
| /** |
| * See {@link #fromStaticMethods} for a detailed description of the characteristics of this {@link |
| * CoderProvider}. |
| */ |
| private static class CoderProviderFromStaticMethods extends CoderProvider { |
| |
| @Override |
| public <T> Coder<T> coderFor(TypeDescriptor<T> type, List<? extends Coder<?>> componentCoders) |
| throws CannotProvideCoderException { |
| if (!this.rawType.equals(type.getRawType())) { |
| throw new CannotProvideCoderException( |
| String.format( |
| "Unable to provide coder for %s, this factory can only provide coders for %s", |
| type, this.rawType)); |
| } |
| try { |
| return (Coder) factoryMethod.invoke(null /* static */, componentCoders.toArray()); |
| } catch (IllegalAccessException |
| | IllegalArgumentException |
| | InvocationTargetException |
| | NullPointerException |
| | ExceptionInInitializerError exn) { |
| throw new IllegalStateException( |
| "error when invoking Coder factory method " + factoryMethod, exn); |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| // Type raw type used to filter the incoming type on. |
| private final Class<?> rawType; |
| |
| // Method to create a coder given component coders |
| // For a Coder class of kind * -> * -> ... n times ... -> * |
| // this has type Coder<?> -> Coder<?> -> ... n times ... -> Coder<T> |
| private final Method factoryMethod; |
| |
| /** Returns a CoderProvider that invokes the given static factory method to create the Coder. */ |
| private CoderProviderFromStaticMethods(Class<?> rawType, Class<?> coderClazz) { |
| this.rawType = rawType; |
| this.factoryMethod = getFactoryMethod(coderClazz); |
| } |
| |
| /** |
| * Returns the static {@code of} constructor method on {@code coderClazz} if it exists. It is |
| * assumed to have one {@link Coder} parameter for each type parameter of {@code coderClazz}. |
| */ |
| private Method getFactoryMethod(Class<?> coderClazz) { |
| Method factoryMethodCandidate; |
| |
| // Find the static factory method of coderClazz named 'of' with |
| // the appropriate number of type parameters. |
| int numTypeParameters = coderClazz.getTypeParameters().length; |
| Class<?>[] factoryMethodArgTypes = new Class<?>[numTypeParameters]; |
| Arrays.fill(factoryMethodArgTypes, Coder.class); |
| try { |
| factoryMethodCandidate = coderClazz.getDeclaredMethod("of", factoryMethodArgTypes); |
| } catch (NoSuchMethodException | SecurityException exn) { |
| throw new IllegalArgumentException( |
| "cannot register Coder " |
| + coderClazz |
| + ": " |
| + "does not have an accessible method named 'of' with " |
| + numTypeParameters |
| + " arguments of Coder type", |
| exn); |
| } |
| if (!Modifier.isStatic(factoryMethodCandidate.getModifiers())) { |
| throw new IllegalArgumentException( |
| "cannot register Coder " |
| + coderClazz |
| + ": " |
| + "method named 'of' with " |
| + numTypeParameters |
| + " arguments of Coder type is not static"); |
| } |
| if (!coderClazz.isAssignableFrom(factoryMethodCandidate.getReturnType())) { |
| throw new IllegalArgumentException( |
| "cannot register Coder " |
| + coderClazz |
| + ": " |
| + "method named 'of' with " |
| + numTypeParameters |
| + " arguments of Coder type does not return a " |
| + coderClazz); |
| } |
| try { |
| if (!factoryMethodCandidate.isAccessible()) { |
| factoryMethodCandidate.setAccessible(true); |
| } |
| } catch (SecurityException exn) { |
| throw new IllegalArgumentException( |
| "cannot register Coder " |
| + coderClazz |
| + ": " |
| + "method named 'of' with " |
| + numTypeParameters |
| + " arguments of Coder type is not accessible", |
| exn); |
| } |
| |
| return factoryMethodCandidate; |
| } |
| |
| @Override |
| public String toString() { |
| return MoreObjects.toStringHelper(getClass()) |
| .add("rawType", rawType) |
| .add("factoryMethod", factoryMethod) |
| .toString(); |
| } |
| } |
| |
| /** See {@link #forCoder} for a detailed description of this {@link CoderProvider}. */ |
| private static class CoderProviderForCoder extends CoderProvider { |
| private final Coder<?> coder; |
| private final TypeDescriptor<?> type; |
| |
| public CoderProviderForCoder(TypeDescriptor<?> type, Coder<?> coder) { |
| this.type = type; |
| this.coder = coder; |
| } |
| |
| @Override |
| public <T> Coder<T> coderFor(TypeDescriptor<T> type, List<? extends Coder<?>> componentCoders) |
| throws CannotProvideCoderException { |
| if (!this.type.equals(type)) { |
| throw new CannotProvideCoderException( |
| String.format( |
| "Unable to provide coder for %s, this factory can only provide coders for %s", |
| type, this.type)); |
| } |
| return (Coder) coder; |
| } |
| |
| @Override |
| public String toString() { |
| return MoreObjects.toStringHelper(getClass()) |
| .add("type", type) |
| .add("coder", coder) |
| .toString(); |
| } |
| } |
| } |