Copy a model object in java

Question

What is the best way if I want to copy a model object in java. Because writing copy() function for a nested object in java becomes a lot of works. I just want to avoid that. As a shortcut I use this approach.

    public static <T> T copy(T model, Class<T> tClass) throws Exception {
        final ObjectMapper objectMapper = new ObjectMapper();
        final byte[] bytes = objectMapper.writeValueAsBytes(model);
        final T copy = objectMapper.readValue(bytes, tClass);
        return copy;
    }

And use it like this.

    final McTrack copy = copy(new McTrack(), McTrack.class);

I have made a Utility function copy() that takes a model object and returns a copy of that. First I serialize the entire object into json and then deserialize it again to make a copy. But I am not sure it really efficient. Is there any better way to copy plain old java objects.

Answer 1

You can also use Dozer library: http://dozer.sourceforge.net/

You can easily copy whole POJOs from one to another like this:

Mapper mapper = new DozerBeanMapper();
DestinationObject destObject = mapper.map(sourceObject, DestinationObject.class);

What is really usufull you can configure your own mappings like this:

<mapping>
  <class-a>yourpackage.yourSourceClassName</class-a>
  <class-b>yourpackage.yourDestinationClassName</class-b>
    <field>
      <a>yourSourceFieldName</a>
      <b>yourDestinationFieldName</b>
    </field>
</mapping> 

Additionally you can use different Technics to copy object, use custom factories, special getters/setters and a lot useful things: http://dozer.sourceforge.net/documentation/mappings.html