Enum factory-style method

Question

In my application, several different reports can be generated (CSV, HTML, etc).

Instead of creating a traditional factory-style method pattern, I was planning on adding a method to the body of enum constants that would create and return the appropriate report object.

public enum ReportType {
 CSV {
  @Override
  public Report create() {
   return new CSVReport();
  }
 },
 HTML {
  @Override
  public Report create() {
   return new HTMLReport();
  }
 };

 public abstract Report create();
}

With a specified ReportType enum constant, I could then easily create a new report by executing a statement like the following:

ReportType.CSV.create()

I wanted to get the opinion of others on using this approach. What do you think of this? Would you prefer any other approach, and if so, why?

Thanks

Answer 1

I think both approaches are ok, but if you don't want to know which kind of report you're generating then I believe that the enum approach is the best. Like so:

public class Person { 
    private String name;
    private ReportType myPreferedReportType;

    public ReportType getMyPreferedReportType(){
        return this.myPreferedReportType;
    }
    //other getters & setters...
}

supose you persist a Person instance on a database and retrieve it later on - if you use polimorphism you won't need any switch wathsoever. The only thing you'll need to do is to call the create() method. Like:

Person person = null; 
//... retrieve the person instance from database and generate a 
//report with his/her prefered report type...
Report report = person.getReportType.create();

So if you rely on polimorphism you won't need to ask a factory to get you the CVS/HTML/PDF explicitly, leaving that work to the Enum itself. But of course, there are situations that you may need to use one or another, although I tend to use the enum approach regularly.

Answer 2

What is the advantage you gain by using enum for instance of Report creation ? If you had factory-method you would have created an instance of CSVReport (say) like below:

Report csvReport = ReportFactory.createCSVReport();

which I think conveys the intent better than the enum. As I understand Enumerations represent a fixed set of constants, and using it as a factory for instance creation (though works) seems to me misuse of the intent of Enumeration.