从枚举到类型的泛型映射

Question

I am writing a class that writes data (defined per interface) to different xml- output formats (different JAXB-Classes). All supported types are stored in an Enum (SupportedTypes). The Enum stores the the corresponding JAXB-Class. The enum looks like this:

public enum Types {
/**
 * Invoice from hospitals.
 */
Type1(...generatedClasses.invoice.hospital400.request.RequestType.class),
/**
 * Invoice from hospital but with MediData's quality extensions. The
 * response has no extensions.
 */
Type2(...generatedClasses.invoice.hospital400_QO.request.RequestType.class);

/**
 * Class for request. represents the root element in corresponding xml.
 */
private Class<?> rType;

/**
 * 
 * @param requestType
 *            class of corresponding request type
 */
private InvoiceTypes(final Class<?> requestType) {
    this.requestType = requestType;
}

/**
 * @return the requestType
 */
public final Class<?> getRequestType() {
    return requestType;
}

}

My problem is how to use this types to instantiate typed generics like JAXBElement. The typeEnum is given as parameter and i want to create JAXBElement but this is obviously not working. Now i'am stuck. How to construct such a constructer or method.

thx in advance

Edit for clarification:

Lets assume you create a class ("ClassForTypes") that supports different types - for whatever it does with them (TheirClass, SpecialClass, MyClass). The api will not publish those classes (they are very specific) but instead it will publish an "TypeEnum" (TypeOne, TypeTwo, TypeThree) that stores the types of the classes (TheirClass, SpecialClass, MyClass). At construction time of ClassForTypes it will use the given TypeEnum to create let's say a List<type saved in enum> . How to construct such a ClassForTypes or it's constructor?

Some example code (does not work): The enum from above i want to use this way:

public class Blub{

    public Blub(Types type){
        List<type.getRequestType> typedList = new ArrayList...
    }

}

This does not work. But the type for the list is known on compile time (because it is stored in an enum?). Is there any way to statically store a type and use it to get a typed generic? I don't want the api user knows something about the single request types the user should only know about "supported types" delivered via the enum.

Answer 1

Your question is not too clear on exactly what you want to do. Are you trying to add functionality to your enum? Something like this?

public enum Types {
  Type1(String.class) {
    @Override
    public Object make () {
      return new String();
    }
  },
  Type2(Integer.class) {
    @Override
    public Object make () {
      return new Integer(0);
    }
  };

  private Class<?> rType;

  Types(final Class<?> requestType) {
    this.rType = requestType;
  }

  public final Class<?> getRequestType() {
    return rType;
  }

  // All types must have a make method.
  public abstract Object make();
}