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I don't use design patterns very often, besides an occasional factory and MVC, and I want to start using them more.

I have a concrete case at hand that I would like your opinion on the use of design patterns in this case.

In my application I have to convert objects pretty often in different situations. I might have to convert a Hibernate POJO to a DTO, because I use GWT and Hibernate POJO's aren't serializable and can't be sent over the line.

In another situation I might need to convert Java objects to SolrInputDocument's for indexing by Solr.

I would like to know if I should use a design pattern for this. It seems that "object conversion" is a generic task that could be handled in a flexible/abstract way by a pattern, but I don't really see how.

Without patterns I would just create a separate class for each type of conversion, for example CourseToSolrInputDocument (Course is a Hibernate entity in my application). Or CourseToCourseDTO. Each of these conversion classes might have a single static method called convert() that takes the source object as input and returns the output object.

But that is not really a pattern, is it? So I started of on something with generics and created this class that implements the Converter interface. But is somehow feels silly tgo create a generic interface and I don't really see the advantage other than being able to congratulate myself on the use of generics.

public class CourseToSolrInputDocument implements Converter<Course, SolrInputDocument>         {
    @Override
    public void convert(Course source, SolrInputDocument destination) {
        //To change body of implemented methods use File | Settings | File Templates.
    }
}

So, the real question here is: is there a pattern that applies to generic object conversion and, what would be your approach and what are the advantages over using just a class-per-conversion type approach?

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  • Patterns are more of names for what you do (and example how to do it properly), than something awsome to use. So better question than how can I use more patterns is: What patters I already use (maybe in some incomplete/convoluted way).
    – user470365
    Jan 31, 2013 at 9:27

1 Answer 1

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18

The Translator Pattern is what you're asking for.

But I suspect what you're looking for is a framework, more than a pattern. I believe Dozer is popular in the Java world.

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  • I know Dozer and Apache Beanutils. I would like to use one of those inside my "conversion structure". I the meantime I found that Spring offers a solution for converting objects that can be found here: static.springsource.org/spring/docs/3.0.0.RC3/reference/html/… . I had seen it before, but a long time ago, so my own interface was kind of based on what I remembered from Spring. I am going to go with the Spring solution, because Spring is already in my project and it looks like a good approach.
    – Julius
    Feb 1, 2013 at 11:51

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