Download files & filename

[cleric]

Hello.

In my application users can upload and download files. And they want to download files with names which they upload. Those can be files with names on different languages. So, i must return their names in UTF-8 encoding.
But the Seam

DocumentStoreServlet

doesn't apply any encoding for this approach.
For some research i'd gone for conclusion: seam doesn't support all existing browsers.
i took the DocumentStoreServlet class and I wrote own. It is his source:

public class MyDocumentStoreServlet extends HttpServlet {
    private static final String ENCODING = "UTF-8";

    protected void doGet(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {
        new ContextualHttpServletRequest(request) {
            @Override
            public void process() throws ServletException, IOException {
                doWork(request, response);
            }
        }.run();
    }

    private static void doWork(HttpServletRequest request, HttpServletResponse response) throws IOException {
        Parameters params = Parameters.instance();
        String contentId = (String) params.convertMultiValueRequestParameter(params.getRequestParameters(), "docId", String.class);

        DocumentStore store = DocumentStore.instance();

        if (store.idIsValid(contentId)) {
            DocumentData documentData = store.getDocumentData(contentId);

            response.setContentType(documentData.getDocumentType().getMimeType());

            new ContentDispositionBuilder(request, response, documentData).build();

            documentData.writeDataToStream(response.getOutputStream());
        } else {
            String error = store.getErrorPage();
            if (error != null) {
                if (error.startsWith("/")) {
                    error = request.getContextPath() + error;
                }
                response.sendRedirect(error);
            } else {
                response.sendError(404);
            }
        }
    }

    private static class ContentDispositionBuilder {
        private HttpServletRequest request;

        private HttpServletResponse response;

        private DocumentData documentData;

        private String userAgent;

        private ContentDispositionBuilder(HttpServletRequest request, HttpServletResponse response, DocumentData documentData) {
            this.request = request;
            this.response = response;
            this.documentData = documentData;
        }

        public void build() throws UnsupportedEncodingException {
            userAgent = request.getHeader("User-Agent").toLowerCase();

            String fileName = buildFileName();

            String fileNameAttr = "filename=";

            if (isIE() || isChrome()) {
                fileName = "\"" + fileName + "\"";
            } else {
                fileNameAttr = fileNameAttr.replace("=", "*=") + ENCODING + "''";
            }

            response.setHeader("Content-Disposition", documentData.getDisposition() + "; " + fileNameAttr + fileName);
        }

        private String buildFileName() throws UnsupportedEncodingException {
            String fileName = documentData.getFileName();
            return URLEncoder.encode(fileName, ENCODING).replaceAll("\\+", "%20");
        }

        private boolean isFirefox() {
            return userAgent.contains("gecko");
        }

        private boolean isIE() {
            return userAgent.contains("msie");
        }

        private boolean isOpera() {
            return userAgent.contains("opera");
        }

        private boolean isChrome() {
            return userAgent.contains("webkit");
        }
    }
}

It is a sample of usage this approche:
1. My facelet messageFile.xhtml:

<s:resource xmlns="http://www.w3.org/1999/xhtml"
            xmlns:s="http://jboss.com/products/seam/taglib"
            data="#{messageFileResource.body}"
            fileName="#{messageFileResource.fileName}"/>

and second sample:

<s:resource xmlns="http://www.w3.org/1999/xhtml"
            xmlns:s="http://jboss.com/products/seam/taglib"
            data="#{reqDocumentResource.body}"
            fileName="#{reqDocumentResource.fileName}"/>

2. My component:

public abstract class DownloadFileResource<T> {
    protected byte[] body;

    protected String fileName;

    public byte[] getBody() {
        return body;
    }

    public String getFileName() {
        return fileName;
    }

    protected abstract String buildFileName(T o);
}

3. And implementation:

@Name("messageFileResource")
@Scope(ScopeType.EVENT)
public class MessageFileResource extends DownloadFileResource<MessageFile> {
    @RequestParameter
    private String name;

    @RequestParameter
    private Long messageId;

    @In
    private EntityHome<MessageFile> messageFileHome;

    @Create
    public void create() throws UnsupportedEncodingException {
        MessageFilePk pk = new MessageFilePk(new Message(messageId), name);
        messageFileHome.setId(pk);
        MessageFile file = messageFileHome.getInstance();
        body = file.getFileBody();
        fileName = buildFileName(file);
        messageFileHome.clearInstance();
    }

    @Override
    protected String buildFileName(MessageFile o) {
        return o.getId().getFileName() + "." + o.getContentType();
    }
}

In my logic the ContentType is the file extension.

I think my solution may help for many developers who make applications with internationalized interface and they is cross-browser.