Hi! I've just re-read your reply, but I cant understand how the
interface would affect the program, and how would I use that new
getDocument() method of the XmlUtilParser class. Could you provide
another example (a working one, if possible)?
This whole AsyncCallback/asynchronous stuff of GWT is driving me nuts.
I've created the same parser using a service, and Java's own DOM
parser, and it works already, however I really want to develop this
app of mine full GWT-style. Hope you could help me again, thanks.
On Nov 10, 5:58 pm, Jason Morris <[EMAIL PROTECTED]> wrote:
> Heya,
>
> Your basic problem here is that you can't have your XmlParserUtil return a
> Document object. The doc field will only be filled in when the async
> RequestBuilder request returns and the parser is finished with the XML string.
> By that time, your method has already returned.
>
> The only way to solve this is to create something like a:
>
> public interface Callback<V> {
> void callback(V value);
>
> }
>
> and have the XmlParserUtil look something more like this:
>
> public class XmlParserUtil {
> String url;
> Document doc;
> public RequestBuilder requestBuilder;
> String xmlStr;
>
> public XmlParserUtil(String xmlFileName) {
> this.url = xmlFileName;
> }
>
> public void getDocument(Callback<Document> callback) {
> if(doc != null) {
> callback.callback(doc);
> return;
> }
>
> try {
> requestBuilder = new
> RequestBuilder(RequestBuilder.GET,url);
> requestBuilder.sendRequest(null,new RequestCallback()
> {public void onResponseReceived(Request arg0,
> Response arg1) {
> xmlStr = arg1.getText();
> callback.callback(doc =
> XMLParser.parse(xmlStr));
> }
> public void onError(Request request, Throwable
> exception) {
>
> }});
> }
> catch (RequestException ex) {
> GWT.log(ex.getMessage(), ex);
> }
> }
>
> }
>
> For more information about async problems, it's related to RPC, but applicable
> to the RequestBuilder as well:
>
> http://lemnik.wordpress.com/2008/07/04/gwt-rpc-is-called-aynchronous-...
>
> mives29 wrote:
> > okay, let me be clear on this, again, my code. (now posting full
> > reworked source code)
>
> > // A composite w/c contains a tree.
> > public class TreeX extends Composite {
> > Document doc;
> > Tree t = new Tree();
> > int imgUris;
> > XmlParserUtil xmlParser;
> > public TreePol() {
> > TreeItem tItem = getTreeItem();
> > t.addItem(tItem);
> > initWidget(t);
> > }
> > private TreeItem getTreeItem() {
> > doc = getDoc();
> > imgUris = doc.getElementsByTagName("Image").getLength();
> > TreeItem root = null;
> > root = new TreeItem("Image Names");
> > for (int i=0;i<imgUris;i++) {
> > String tmpImgUri =
> > doc.getElementsByTagName("Image").item(i).getChildNodes().item(1).toString();
> > root.addItem(tmpImgUri);
> > }
> > return root;
> > }
> > public Document getDoc() {
> > xmlParser = new XmlParserUtil("image_uris.xml");
> > while (doc==null) {
> > doc = xmlParser.getDocument();
> > }
> > return doc;
> > }
> > }
>
> > //A class that i want to use as a utility class for parsing xml
> > documents. intended to be reusable
> > public class XmlParserUtil {
> > String url;
> > Document doc;
> > public RequestBuilder requestBuilder;
> > String xmlStr;
>
> > public XmlParserUtil(String xmlFileName) {
> > this.url = xmlFileName;
> > }
>
> > public Document getDocument() {
> > try {
> > requestBuilder = new
> > RequestBuilder(RequestBuilder.GET,url);
> > requestBuilder.sendRequest(null,new RequestCallback()
> > {public void onResponseReceived(Request arg0, Response
> > arg1) {
> > xmlStr = arg1.getText();
> > doc = XMLParser.parse(xmlStr);
> > }
> > public void onError(Request request, Throwable
> > exception) {
>
> > }});
> > }
> > catch (RequestException ex) {
> > GWT.log(ex.getMessage(), ex);
> > }
> > return doc;
> > }
> > }
>
> > //my entrypoint's onModuleLoad(), which adds the various custom
> > widgets i made to a tab panel
>
> > public void onModuleLoad() {
> > RichTextAreaX1 rtaPol = new RichTextAreaX1();
> > PictureViewer imgBrowser = new PictureViewer();
> > TreeX tree = new TreeX();
>
> > TabPanel tp = new TabPanel();
> > tp.add(tree, "1");
> > tp.add(rtaPol, "2");
> > tp.add(imgBrowser, "3");
>
> > tp.selectTab(0);
> > tp.setWidth("100%");
>
> > RootPanel.get("leftpanel").add(tp);
> > }
>
> > as you can see, I intend the XmlParserUtil class to be reusable. If I
> > place there various logic, then it would be out of scope for that
> > classs, because I intend to use XmlParserUtil just to parse an XML
> > file, and bring me back a parsed Document object. now how would I do
> > that if XmlParserUtil, which contains the requestbuilder and callback,
> > would be used by another class (which is a composite).
>
> > im new to this async thing, more so the requestbuilder stuff. thank
> > you for replying, i hope you could answer my question.
>
> > On Nov 10, 3:44 pm, "alex.d" <[EMAIL PROTECTED]> wrote:
> >> You have to accept the asynchronous nature of RPC-Requests in GWT and
> >> stop trying to build smth. synchronous around them. This code:
> >> -----------------------------------
> >> doc = getDoc(); //(where doc is a Document object)
> >> String subject =
> >> doc.getElementsByTagName("Image").item(0).getChildNodes().item(1).toString();
> >> String subject2 =
> >> doc.getElementsByTagName("Image").item(1).getFirstChild().getNodeValue();
> >> -----------------------------------
> >> should not be executed in the onload-routine but in the
> >> onResponseReceived()-method (or in any other procedure that you call
> >> out of it).
>
> >> On 10 Nov., 07:12, mives29 <[EMAIL PROTECTED]> wrote:
>
> >>> hi all. ive re-done my code just a while ago(been a busy week) and my
> >>> code kinda bothers me. here's the code re-done:
> >>> Entrypoint onModuleLoad() method:
> >>> doc = getDoc(); //(where doc is a Document object)
> >>> String subject =
> >>> doc.getElementsByTagName("Image").item(0).getChildNodes().item(1).toString();
> >>> String subject2 =
> >>> doc.getElementsByTagName("Image").item(1).getFirstChild().getNodeValue();
> >>> Entrypoiny getDoc() method:
> >>> public Document getDoc() {
> >>> XmlParserUtil xmlParser = new XmlParserUtil("image_uris.xml");
> >>> int i = 0;
> >>> while (doc==null) {
> >>> doc = xmlParser.getDocument();
> >>> }
> >>> return doc;
> >>> }
> >>> here's the service implementation:
> >>> public class XmlParserUtil {
> >>> String url;
> >>> Document doc;
> >>> RequestBuilder requestBuilder;
> >>> public String xmlStr;
> >>> public XmlParserUtil(String xmlFileName) {
> >>> this.url = xmlFileName;
> >>> }
> >>> public Document getDocument() {
> >>> RequestCallback xmlRcb = new RequestCallback()
> >>> {public void onResponseReceived(Request arg0, Response
> >>> arg1) {
> >>> xmlStr = arg1.getText();
> >>> doc = XMLParser.parse(xmlStr);
> >>> }
> >>> public void onError(Request request, Throwable exception)
> >>> {
> >>> // TODO Auto-generated method stub
> >>> }};
> >>> try {
> >>> requestBuilder = new
> >>> RequestBuilder(RequestBuilder.GET,url);
> >>> requestBuilder.sendRequest(null,xmlRcb);
> >>> }
> >>> catch (RequestException ex) {
> >>> GWT.log(ex.getMessage(), ex);
> >>> }
> >>> return doc;
> >>> }
> >>> }
> >>> my problem is on the Entrypoint logic. you see the getDoc() method
> >>> there?
> >>> it has this:
> >>> while (doc==null) {
> >>> doc = xmlParser.getDocument();
> >>> }
> >>> which just loops around until the service implementation has already
> >>> populated the parsed document.
> >>> what bothers me with this code is that it seems to break AJAX. the
> >>> execution "stays" here until the document object is not null anymore,
> >>> which kills the purpose of using AJAX (coz it seems not asynchronous
> >>> anymore).
> >>> is there any lister that i can implement on my entrypoint class that
> >>> "listens" if the service has already received a reply? (or a listener
> >>> of that sort)
> >>> thanks in advance.
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