Factory pattern for getting xml data

Question

i am trying to implement factory pattern for getting XML Document from server

(using javax.xml.parsers.DocumentBuilder)

I have the classes below for now, could you give your opinion ? Does the structure make sense for this pattern?

DocumentGeneratorFactory (abstract factory)

public interface DocumentGeneratorFactory {
 public Document createDocument(String scheme, String authority,
 String path, HashMap<String, String> parameters)
 throws ParserConfigurationException, SAXException, IOException;
 public Document createDocument(String scheme, String authority,String path)
 throws ParserConfigurationException, SAXException, IOException;
}

ProductDocumentGeneratorFactory (Concreate factory)

public class ProductDocumentGeneratorFactory implements
 DocumentGeneratorFactory {
 public Document createDocument(String scheme, String authority,
 String path, HashMap<String, String> parameters)
 throws ParserConfigurationException, SAXException, IOException {
 Uri.Builder uri = new Uri.Builder();
 uri.scheme(scheme);
 uri.authority(authority);
 uri.path(path);
 Set<Map.Entry<String, String>> set = parameters.entrySet();
 for (Map.Entry<String, String> params : set) {
 uri.appendQueryParameter(params.getKey(), params.getValue());
 }
 URL url = new URL(uri.toString());
 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
 DocumentBuilder db = dbf.newDocumentBuilder();
 Document doc = db.parse(new InputSource(url.openStream()));
 doc.getDocumentElement().normalize();
 return doc;
 }
 public Document createDocument(String scheme, String authority, String path)
 throws ParserConfigurationException, SAXException, IOException {
 Uri.Builder uri = new Uri.Builder();
 uri.scheme(scheme);
 uri.authority(authority);
 uri.path(path);
 URL url = new URL(uri.toString());
 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
 DocumentBuilder db = dbf.newDocumentBuilder();
 Document doc = db.parse(new InputSource(url.openStream()));
 doc.getDocumentElement().normalize();
 return doc;
 }
}

Request (Abstract Product)

public abstract class Request {
 Document doc;
 HashMap<String, String> queryStrings;
 abstract void prepareRequest() throws ParserConfigurationException, SAXException, IOException; 
}

ProductRequest (Product)

public class ProductRequest extends Request{
 ProductDocumentGeneratorFactory DocumentGeneratorFactory; 
 HashMap<String, String> queryStrings;
 public ProductRequest(ProductDocumentGeneratorFactory DocumentGeneratorFactory,HashMap<String, String> queryStrings){
 this.DocumentGeneratorFactory = DocumentGeneratorFactory;
 this.queryStrings = queryStrings;
 }
 @Override
 void prepareRequest() throws ParserConfigurationException, SAXException, IOException {
 doc = this.DocumentGeneratorFactory.createDocument("http", "ip-address", "default.aspx",this.queryStrings); 
 }
}

Answer 1

Makes sense, but you should DRY up your concrete factory at least. Forgive me my rusty Java, but something like this:

public class ProductDocumentGeneratorFactory implements
 DocumentGeneratorFactory {
 public Document createDocument(String scheme, String authority, String path)
 throws ParserConfigurationException, SAXException, IOException {
 Uri.Builder uri = createUri(scheme, authority, path);
 Document doc = createDocument(uri);
 return doc;
 }
 public Document createDocument(String scheme, String authority,
 String path, HashMap<String, String> parameters)
 throws ParserConfigurationException, SAXException, IOException {
 Uri.Builder uri = createUri(scheme, authority, path);
 appendParameters(uri, parameters);
 Document doc = createDocument(Uri.Builder uri);
 return doc;
 }
 private Uri createUri(string scheme, string authority, string path)
 {
 Uri.Builder uri = new Uri.Builder();
 uri.scheme(scheme);
 uri.authority(authority);
 uri.path(path);
 return uri;
 }
 private Document createDocument(Uri.Builder uri)
 {
 URL url = new URL(uri.toString());
 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
 DocumentBuilder db = dbf.newDocumentBuilder();
 Document doc = db.parse(new InputSource(url.openStream()));
 doc.getDocumentElement().normalize();
 return doc
 }
 private void appendParameters(Uri.Builder uri, HashMap<string,string> parameters)
 {
 Set<Map.Entry<String, String>> set = parameters.entrySet();
 for (Map.Entry<String, String> params : set) {
 uri.appendQueryParameter(params.getKey(), params.getValue());
 }
 }
}

Of course you can expand on that by employing the template pattern for the extra parameter settings.

I would also look into extracting the parameters to a "parameter object" instead of several parameters.