为什么spring DefaultSerializer的serialize方法没有关闭ObjectOutputStream

代码如下：ObjectOutputStream没有调用close方法，只调用了flush方法，难道不需要关闭么

public class DefaultSerializer implements Serializer<Object> {
 
    /**
     * Writes the source object to an output stream using Java Serialization.
     * The source object must implement {@link Serializable}.
     */
    public void serialize(Object object, OutputStream outputStream) throws IOException {
        if (!(object instanceof Serializable)) {
            throw new IllegalArgumentException(getClass().getSimpleName() + " requires a Serializable payload " +
                    "but received an object of type [" + object.getClass().getName() + "]");
        }
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
        objectOutputStream.writeObject(object);
        objectOutputStream.flush();
    }
 
}