避免代码重复的Java通用参数方法

Question

I have a function that parse an object. But this function is required in two services and the parameter have same class name, but different package name. What i need is to avoid duplicated code.

Suppose the function is:

    private HashMap<String, Integer> getPagination(PagingRequestType pagingRequestType) {
        int pageSize = 200;
        int pageNumber = 1;
        if(pagingRequestType != null) {
            if (pagingRequestType.getNumberOfRecordsPerPage() != 0) {
                pageSize = pagingRequestType.getNumberOfRecordsPerPage();
            }
            if (pagingRequestType.getStartAtRecordNumber() != 0) {
                pageNumber = pagingRequestType.getStartAtRecordNumber();
            }
        }
        HashMap<String, Integer> result = new HashMap<>();
        result.put("pageNumber", pageNumber);
        result.put("pageSize", pageSize);
        return result;
    }

Possible function calls:

- getPagination(new Abc.PagingRequestType());
- getPagination(new Xyz.PagingRequestType());

PagingRequestType is an auto-generated class in two different packages. The function needs to be implemented once and used in both services.

Thanks.

Answer 1

If you can modify your PagingRequestType classes, it will be a good idea to use a common interface:

class Abc.PagingRequestType implements PagingRequestType
class Xyz.PagingRequestType implements PagingRequestType

interface PagingRequestType {
    getNumberOfRecordsPerPage();
    getStartAtRecordNumber();
}

Answer 2

The obvious answer is not to auto-generate PagingRequestType in two places.

If you can't do this, you need the two classes to implement a common interface, through which the requisite fields ( getNumberOfRecordsPerPage and getStartAtRecordNumber ) are available.

If you can't change the classes, you can create an interface with these fields:

interface YourInterface {
  int getNumberOfRecordsPerPage();
  int getStartAtRecordNumber();
}

and implement for the two PagingRequestType s:

class AbcYourInterface implements YourInterface {
  final Abc.PagingRequestType delegate;  // Set in constructor.

  @Override public int getNumberOfRecordsPerPage() {
   return delegate.getNumberOfRecordsPerPage();
  }

  // Same for other method.
}

If all else fails, pass in the class fields as separate parameters:

private HashMap<String, Integer> getPagination(int numberOfRecordsPerPage, int startAtRecordNumber) {

using some "special" value to indicate null , eg 0, since the conditional is a no-op if both parameters are zero.

Answer 3

Both PagingRequestType could implement one common interface or extend one common class and you could take this "common part" as argument to your function. Although I don't know if you can modify your auto generated code in that way.

Answer 4

If the option to make those two PagingRequestType s to implement a common interface is impossiable, you could do it the reverse way, define a proxy type to wrap those two types:

public final class PagingRequestTypeProxy {
    private a.b.c.PagingRequestType abcPagingRequestType;

    private a.b.d.PagingRequestType abdPagingRequestType;

    public PagingRequestTypeProxy(PagingRequestType abcPagingRequestType) {
        this.abcPagingRequestType = abcPagingRequestType;
    }

    public PagingRequestTypeProxy(a.b.d.PagingRequestType abdPagingRequestType) {
        this.abdPagingRequestType = abdPagingRequestType;
    }

    public int getNumberOfRecordsPerPage() {
        return abcPagingRequestType != null ? abcPagingRequestType.getNumberOfRecordsPerPage() : abdPagingRequestType.getNumberOfRecordsPerPage();
    }

    public int getStartAtRecordNumber() {
        return abcPagingRequestType != null ? abcPagingRequestType.getStartAtRecordNumber() : abdPagingRequestType.getStartAtRecordNumber();
    }
}

And change the parameter type of getPagination to:

private HashMap<String, Integer> getPagination(PagingRequestTypeProxy pagingRequestType) {...}

Then you could use it like:

getPagination(new PagingRequestTypeProxy(abcPagingReqType));
getPagination(new PagingRequestTypeProxy(abdPagingReqType));

The cons is that there're extra codes to define PagingRequestTypeProxy , the pros is that logic of PagingRequestTypeProxy is very simple and easy to maintain, and you can put your biz code getPagination in one place.