content: /*
   * 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 edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.OutputStream;
  import java.io.Serializable;
  import java.lang.reflect.Method;
  import java.util.Collections;
  import java.util.List;
  import java.util.Set;
  import java.util.WeakHashMap;
  import org.apache.beam.sdk.PipelineRunner;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableList;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A {@link Coder} for Java classes that implement {@link Serializable}.
   *
   * <p>{@link SerializableCoder} should be used only for objects that have proper {@link
   * Object#equals} and {@link Object#hashCode} implementations.
   *
   * <p>To use, specify the coder type on a PCollection:
   *
   * <pre>{@code
   * PCollection<MyRecord> records =
   *     foo.apply(...).setCoder(SerializableCoder.of(MyRecord.class));
   * }</pre>
   *
   * <p>{@link SerializableCoder} does not guarantee a deterministic encoding, as Java serialization
   * may produce different binary encodings for two equivalent objects.
   *
   * @param <T> the type of elements handled by this coder
   */
  public class SerializableCoder<T extends Serializable> extends CustomCoder<T> {
  
    /*
     * A thread safe set containing classes which we have warned about.
     * Note that we specifically use a weak hash map to allow for classes to be unloaded.
     */
    private static final Set<Class<?>> MISSING_EQUALS_METHOD =
        Collections.synchronizedSet(Collections.newSetFromMap(new WeakHashMap<>()));
  
    private static final Logger LOG = LoggerFactory.getLogger(SerializableCoder.class);
  
    /**
     * Returns a {@link SerializableCoder} instance for the provided element type.
     *
     * @param <T> the element type
     */
    public static <T extends Serializable> SerializableCoder<T> of(TypeDescriptor<T> type) {
      @SuppressWarnings("unchecked")
      Class<T> clazz = (Class<T>) type.getRawType();
      return new SerializableCoder<>(clazz, type);
    }
  
    @Override
    public boolean consistentWithEquals() {
      return false;
    }
  
    /**
     * The structural value of the object is the object itself. The {@link SerializableCoder} should
     * be only used for objects with a proper {@link Object#equals} implementation.
     */
    @Override
    public Object structuralValue(T value) {
      return value;
    }
  
    /**
     * Returns a {@link SerializableCoder} instance for the provided element class.
     *
     * @param <T> the element type
     */
    public static <T extends Serializable> SerializableCoder<T> of(Class<T> clazz) {
      checkEqualsMethodDefined(clazz);
      return new SerializableCoder<>(clazz, TypeDescriptor.of(clazz));
    }
  
    private static <T extends Serializable> void checkEqualsMethodDefined(Class<T> clazz) {
      boolean warn = true;
      if (!clazz.isInterface()) {
        Method method;
        try {
          method = clazz.getMethod("equals", Object.class);
        } catch (NoSuchMethodException e) {
          // All concrete classes have an equals method declared in their class hierarchy.
          throw new AssertionError(String.format("Concrete class %s has no equals method", clazz));
        }
        // Check if not default Object#equals implementation.
        warn = Object.class.equals(method.getDeclaringClass());
      }
  
      // Note that the order of these checks is important since we want the
      // "did we add the class to the set" check to happen last.
      if (warn && MISSING_EQUALS_METHOD.add(clazz)) {
        LOG.warn(
            "Can't verify serialized elements of type {} have well defined equals method. "
                + "This may produce incorrect results on some {} implementations",
            clazz.getSimpleName(),
            PipelineRunner.class.getSimpleName());
      }
    }
  
    /**
     * Returns a {@link CoderProvider} which uses the {@link SerializableCoder} if possible for all
     * types.
     *
     * <p>This method is invoked reflectively from {@link DefaultCoder}.
     */
    @SuppressWarnings("unused")
    public static CoderProvider getCoderProvider() {
      return new SerializableCoderProvider();
    }
  
    /**
     * A {@link CoderProviderRegistrar} which registers a {@link CoderProvider} which can handle
     * serializable types.
     */
    public static class SerializableCoderProviderRegistrar implements CoderProviderRegistrar {
  
      @Override
      public List<CoderProvider> getCoderProviders() {
        return ImmutableList.of(getCoderProvider());
      }
    }
  
    /**
     * A {@link CoderProvider} that constructs a {@link SerializableCoder} for any class that
     * implements serializable.
     */
    static class SerializableCoderProvider extends CoderProvider {
      @Override
      public <T> Coder<T> coderFor(
          TypeDescriptor<T> typeDescriptor, List<? extends Coder<?>> componentCoders)
          throws CannotProvideCoderException {
        if (Serializable.class.isAssignableFrom(typeDescriptor.getRawType())) {
          return SerializableCoder.of((TypeDescriptor) typeDescriptor);
        }
        throw new CannotProvideCoderException(
            "Cannot provide SerializableCoder because "
                + typeDescriptor
                + " does not implement Serializable");
      }
    }
  
    private final Class<T> type;
  
    /**
     * Access via {@link #getEncodedTypeDescriptor()}.
     *
     * <p>The field is restored lazily if it is not present due to serialization.
     */
    @SuppressFBWarnings("SE_TRANSIENT_FIELD_NOT_RESTORED")
    private transient @Nullable TypeDescriptor<T> typeDescriptor;
  
    protected SerializableCoder(Class<T> type, TypeDescriptor<T> typeDescriptor) {
      this.type = type;
      this.typeDescriptor = typeDescriptor;
    }
  
    public Class<T> getRecordType() {
      return type;
    }
  
    @Override
    public void encode(T value, OutputStream outStream) throws IOException {
      ObjectOutputStream oos = new ObjectOutputStream(outStream);
      oos.writeObject(value);
      oos.flush();
    }
  
    @Override
    public T decode(InputStream inStream) throws IOException, CoderException {
      try {
        ObjectInputStream ois = new ObjectInputStream(inStream);
        return type.cast(ois.readObject());
      } catch (ClassNotFoundException e) {
        throw new CoderException("unable to deserialize record", e);
      }
    }
  
    /**
     * {@inheritDoc}
     *
     * @throws NonDeterministicException always. Java serialization is not deterministic with respect
     *     to {@link Object#equals} for all types.
     */
    @Override
    public void verifyDeterministic() throws NonDeterministicException {
      throw new NonDeterministicException(this, "Java Serialization may be non-deterministic.");
    }
  
    @Override
    public boolean equals(@Nullable Object other) {
      return !(other == null || getClass() != other.getClass())
          && type == ((SerializableCoder<?>) other).type;
    }
  
    @Override
    public int hashCode() {
      return type.hashCode();
    }
  
    @Override
    public TypeDescriptor<T> getEncodedTypeDescriptor() {
      if (typeDescriptor == null) {
        typeDescriptor = TypeDescriptor.of(type);
      }
      return typeDescriptor;
    }
  
    @Override
    public String toString() {
      return "SerializableCoder(" + type.getName() + ")";
    }
  
    // This coder inherits isRegisterByteSizeObserverCheap,
    // getEncodedElementByteSize and registerByteSizeObserver
    // from StructuredCoder. Looks like we cannot do much better
    // in this case.
  }
  