How to use

Writeable

in

org.elasticsearch.common.io.stream

/**
 * Writes the specified array of {@link Writeable}s. This method can be seen as
 * writer version of {@link StreamInput#readArray(Writeable.Reader, IntFunction)}. The length of array encoded as a variable-length
 * integer is first written to the stream, and then the elements of the array are written to the stream.
 */
public <T extends Writeable> void writeArray(T[] array) throws IOException {
  writeArray((out, value) -> value.writeTo(out), array);
}

/**
 * Writes a list of {@link Writeable} objects
 */
public void writeList(List<? extends Writeable> list) throws IOException {
  writeVInt(list.size());
  for (Writeable obj: list) {
    obj.writeTo(this);
  }
}

/**
 * Same as {@link #writeArray(Writeable[])} but the provided array may be null. An additional boolean value is
 * serialized to indicate whether the array was null or not.
 */
public <T extends Writeable> void writeOptionalArray(@Nullable T[] array) throws IOException {
  writeOptionalArray((out, value) -> value.writeTo(out), array);
}

public void writeOptionalWriteable(@Nullable Writeable writeable) throws IOException {
  if (writeable != null) {
    writeBoolean(true);
    writeable.writeTo(this);
  } else {
    writeBoolean(false);
  }
}

public <T extends Writeable> void writeArray(T[] array) throws IOException {
  writeVInt(array.length);
  for (T value: array) {
    value.writeTo(this);
  }
}

/**
 * Writes a list of {@link Writeable} objects
 */
public void writeList(List<? extends Writeable> list) throws IOException {
  writeVInt(list.size());
  for (Writeable obj: list) {
    obj.writeTo(this);
  }
}

public <T extends Writeable> void writeArray(T[] array) throws IOException {
  writeVInt(array.length);
  for (T value: array) {
    value.writeTo(this);
  }
}

/**
 * Writes a list of {@link Writeable} objects
 */
public void writeList(List<? extends Writeable> list) throws IOException {
  writeVInt(list.size());
  for (Writeable obj: list) {
    obj.writeTo(this);
  }
}

  /**
   * Writes a list of {@link Writeable} objects
   */
  public <T extends Writeable<T>> void writeList(List<T> list) throws IOException {
    writeVInt(list.size());
    for (T obj: list) {
      obj.writeTo(this);
    }
  }
}

public void writeOptionalWriteable(@Nullable Writeable writeable) throws IOException {
  if (writeable != null) {
    writeBoolean(true);
    writeable.writeTo(this);
  } else {
    writeBoolean(false);
  }
}

public void writeOptionalWriteable(@Nullable Writeable writeable) throws IOException {
  if (writeable != null) {
    writeBoolean(true);
    writeable.writeTo(this);
  } else {
    writeBoolean(false);
  }
}

/**
 * Simulates sending diffs over the wire
 */
public static <T extends Writeable> T copyInstance(T diffs, NamedWriteableRegistry namedWriteableRegistry,
                               Reader<T> reader) throws IOException {
  try (BytesStreamOutput output = new BytesStreamOutput()) {
    diffs.writeTo(output);
    try (StreamInput in = new NamedWriteableAwareStreamInput(output.bytes().streamInput(), namedWriteableRegistry)) {
      return reader.read(in);
    }
  }
}

/**
 * Create a copy of an original {@link Writeable} object by running it through a {@link BytesStreamOutput} and
 * reading it in again using a provided {@link Writeable.Reader}. The stream that is wrapped around the {@link StreamInput}
 * potentially need to use a {@link NamedWriteableRegistry}, so this needs to be provided too (although it can be
 * empty if the object that is streamed doesn't contain any {@link NamedWriteable} objects itself.
 */
public static <T extends Writeable> T copyWriteable(T original, NamedWriteableRegistry namedWritabelRegistry,
    Writeable.Reader<T> reader) throws IOException {
  try (BytesStreamOutput output = new BytesStreamOutput()) {
    original.writeTo(output);
    try (StreamInput in = new NamedWriteableAwareStreamInput(output.bytes().streamInput(), namedWritabelRegistry)) {
      return reader.read(in);
    }
  }
}

protected T copyInstance(T instance, Version version) throws IOException {
  try (BytesStreamOutput output = new BytesStreamOutput()) {
    output.setVersion(version);
    instance.writeTo(output);
    try (StreamInput in = new NamedWriteableAwareStreamInput(output.bytes().streamInput(),
        getNamedWriteableRegistry())) {
      in.setVersion(version);
      return instanceReader().read(in);
    }
  }
}