I seem to be suffering from some fundamental misunderstanding of the way that GWT async calls work and/or how widgets are updated upon receipt of a callback.
I've created the two interfaces as well as the implementation and they seem to be communicating with one another. I make this claim based on reasonable looking data observed while stepping through with the eclipse debugger: the result variable in the onSuccess method below contains what I expect it to and the grid that I am attempting to populate ends up being filled with the data from results upon exit from the loop. However when the onSuccess call returns, no grid is displayed in my GUI as per the uhpScrollPanel.setWidget(uhpGrid) call, and no exceptions of any sort are thrown.
I must be be overlooking something obvious, has anyone got any ideas about where to look?
final ScrollPanel uhpScrollPanel = new ScrollPanel();
uhpVert.add(uhpScrollPanel);
uhpScrollPanel.setSize("100%", "100%");
//build and populate grid
UpdateHistoryServiceAsync uhpService = UpdateHistoryService.Util.getInstance();
uhpService.getUpdateHistory(new AsyncCallback<List<UpdateHistoryEntryBean>>() {
public void onFailure(Throwable caught) {
System.out.println("OnFailure");
caught.printStackTrace();
final Label uhpErrorLabel = new Label("Server Unable to Grab History...");
uhpScrollPanel.setWidget(uhpErrorLabel);
uhpErrorLabel.setSize("100%", "100%");
}
public void onSuccess(List<UpdateHistoryEntryBean> result) {
int length = result.size();
final Grid uhpGrid = new Grid();
uhpScrollPanel.setWidget(uhpGrid);
uhpGrid.setBorderWidth(1);
uhpGrid.setSize("100%", "100%");
uhpGrid.resize(length, 3);
int i = 0;
for (UpdateHistoryEntryBean entry : result) {
uhpGrid.setText(i, 0, String.valueOf(entry.getSourceId()));
uhpGrid.setText(i, 1, entry.getTitle());
uhpGrid.setText(i, 2, entry.getBody());
i++;
}
}
});
Your onSuccess() method is not defined correctly, as a parameter it receives an Object, and you must downcast it afterwards.
Meaning, the signature should be:
public void onSuccess(Object result)
After that, you can explicitly downcast the object you know you got back like so:
List<UpdateHistoryEntryBean> resultList = (List<UpdateHistoryEntryBean>) result;
Well it turns out that the quick fix is to add the grid to a VerticalPanel rather than a ScrollPanel. The question now becomes - why should that matter, and how do we get around this dilemma?
Related
I'm working on a code in a wicket project, where the original devs used the onModelChanged() method quite a lot in Ajax request handling methods. I, for one, however am not a strong believer of this implementation.
In fact, I can't think of any examples, where calling the target.add(...) is inferior to calling the onModelChanged method.
Am I missing some key concepts here?
Example:
public MyComponent extends Panel {
public MyComponent(String id, Component... componentsToRefresh) {
add(new AjaxLink<Void>("someId") {
#Override
public void onClick(AjaxRequestTarget target) {
// some logic with model change
for(Component c: componentsToRefresh) {
c.modelChanged();
}
target.add(componentsToRefresh);
}
};
}
}
Now, there are a couple of things I don't agree with, the very first is the componentsToRefresh parameter, the second is (as the question suggests), the fact that we called c.modelChanged() on all components in that array. My guess would be that it is completely un necessary and instead of a parameter in the constructor, one should just write an empty function in MyComponent and override it, and put the necessary components in there when needed.
I would suggest to use Wicket Event system instead. That is, whenever the AjaxLink is clicked you will broadcast an event:
send(getPage(), Broadcast.BREATH, new MyEventPayload(target));
This will broadcast the event to the current Page and all its components.
Then in any of your components you can listen for events:
#Override
public void onEvent(IEvent event) {
Object payload = event.getPayload();
if (payload instanceof MyEventPayload) {
((MyEventPayload) payload).getTarget().add(this); // or any of my sub-components
event.stop(); // optionally you can stop the broadcasting
}
}
This way you do not couple unrelated components in your application.
See Wicket Guide for more information.
Currently I'm trying to customize SmartGWT's DataSource to work with custom REST services. And I hit into problem with sending update requests when some changes have been made in the ListGrid row. By default only changed cells in the row are sent in update request (as described here). And I want to change this behavior to send all data from the row not just edited. I've already spent a lot of time figuring out how to do this but still can't find a solution. Could you please give me any advice how to change this OOTB behavior? Probably someone has had similar problem and found the solution.
//Override the transformRequest function in DataSource
//
#Override
protected void transformResponse(DSResponse response, DSRequest request,
Object data){
// On Update Operation call will hit the below condition
//
if (dsRequest.getOperationType().equals(DSOperationType.UPDATE)) {
// Get the data from listGird
//
listGrid.getDataAsRecordList()
//Set to request
//
dsRequest.setData();
}
}
Here is the way how I implement sending all data from the row during update request. Probably it will help someone.
I overrode transformRequest method and added there such code:
#Override
protected Object transformRequest(final DSRequest dsRequest) {
...
if (dsRequest.getOperationType = OperationType.UPDATE) {
...
final JavaScriptObject basicJSObject = dsRequest.getOldValues().getJsObj();
final JavaScriptObject latestChanges = dsRequest.getData();
JSOHelper.addProperties(basicJSObject, latestChanges);
// Regexp probably can be optimized
final String resultString = JSON.encode(responseData)
.replaceAll("[,]\\s*[,]", ",")
.replaceAll("^\\s*[,]", "")
.replaceAll("[,]\\s*$", "");
return resultString;
}
...
}
Does anyone know for an example of GWT's CellTable using RequestFactory and that table is being edited? I would like to list objects in a table (each row is one object and each column is one property), be able to easily add new objects and edit. I know for Google's DynaTableRf example, but that one doesn't edit.
I searched Google and stackoverflow but wasn't able to find one. I got a bit confused with RF's context and than people also mentioned some "driver".
To demonstrate where I currently arrived, I attach code for one column:
// Create name column.
Column<PersonProxy, String> nameColumn = new Column<PersonProxy, String>(
new EditTextCell()) {
#Override
public String getValue(PersonProxy person) {
String ret = person.getName();
return ret != null ? ret : "";
}
};
nameColumn.setFieldUpdater(new FieldUpdater<PersonProxy, String>() {
#Override
public void update(int index, PersonProxy object, String value) {
PersonRequest req = FaceOrgFactory.getInstance().requestFactory().personRequest();
PersonProxy eObject = req.edit(object);
eObject.setName(value);
req.persist().using(eObject).fire();
}
});
and my code for data provider:
AsyncDataProvider<PersonProxy> personDataProvider = new AsyncDataProvider<PersonProxy>() {
#Override
protected void onRangeChanged(HasData<PersonProxy> display) {
final Range range = display.getVisibleRange();
fetch(range.getStart());
}
};
personDataProvider.addDataDisplay(personTable);
...
private void fetch(final int start) {
lastFetch = start;
requestFactory.personRequest().getPeople(start, numRows).fire(new Receiver<List<PersonProxy>>() {
#Override
public void onSuccess(List<PersonProxy> response) {
if (lastFetch != start){
return;
}
int responses = response.size();
if (start >= (personTable.getRowCount()-numRows)){
PersonProxy newP = requestFactory.personRequest().create(PersonProxy.class);
response.add(newP);
responses++;
}
personTable.setRowData(start, response);
personPager.setPageStart(start);
}
});
requestFactory.personRequest().countPersons().fire(new Receiver<Integer>() {
#Override
public void onSuccess(Integer response) {
personTable.setRowCount(response+1, true);
}
});
}
I try to insert last object a new empty object. And when user would fill it, I'd insert new one after it. But the code is not working. I says that user is "attempting" to edit a object previously edited by another RequestContext.
Dilemmas:
* am I creating too many context'es?
* how to properly insert new object into celltable, created on the client side?
* on fieldUpdater when I get an editable object - should I insert it back to table or forget about it?
Thanks for any help.
am I creating too many context'es?
Yes.
You should have one context per HTTP request (per fire()), and a context that is not fire()d is useless (only do that if you/the user change your/his mind and don't want to, e.g., save your/his changes).
You actually have only one context to remove here (see below).
Note that your approach of saving on each field change can lead to "race conditions", because a proxy can be edit()ed by at most one context at a time, and it remains attached to a context until the server responds (and once a context is fired, the proxy is frozen –read-only– also until the server responds).
(this is not true in all cases: when onConstraintViolation is called, the context and its proxies are unfrozen so you can "fix" the constraint violations and fire the context again; this should be safe because validation is done on the server-side before any service method is called).
how to properly insert new object into celltable, created on the client side?
Your code looks OK, except that you should create your proxy in the same context as the one you'll use to persist it.
on fieldUpdater when I get an editable object - should I insert it back to table or forget about it?
I'm not 100% certain but I think you should refresh the table (something like setRowData(index, Collections.singletonList(object)))
BTW, the driver people mention is probably the RequestFactoryEditorDriver from the Editor framework. It won't help you here (quite the contrary actually).
I am struggling with an issue using RequestFactory in GWT.
I have a User object : this object has login and password fields and other fields which are of collection type.
public class User {
private String login;
private String password;
private Set<Ressource> ressources;
// Getters and setters removed for brievety
}
I need to persist this object in db so I used RequestFactory because it seems like a CRUD-type operation to me.
Now for the RequestFactory part of the code, this is how I have tried to do it :
I create a UserRequestContext object to create a request object for the new User. Which gives something like :
public interface MyRequestFactory extends RequestFactory {
UserRequestContext userRequestContext();
RessourceRequestContext ressourceRequestContext();
}
and to create the user object I have something like this :
public class UserAddScreen extends Composite {
private UserProxy userProxy;
EventBus eventBus = new SimpleEventBus();
MyRequestFactory requestFactory = GWT.create(MyRequestFactory.class);
...
public UserAddScreen() {
...
requestFactory.initialize(eventBus);
}
public showUserAddScreen() {
// Textbox for password and login
// Listbox for ressources
}
}
I have tried to implement it as a wizard. So at the beginning of the UserAddScreen, I have a
a userProxy object.
This object fields are initialized at each step of the wizard :
the first step is adding the login and password
the second step is adding ressources to the userProxy object.
for this last step, I have two list boxes the first one containing the list of all the ressources i have in my DB table Ressources that I got from RessourceRequestContext.getAllRessource (I have a loop to display them as listbox item with the RessourceId as the value) and the second allows me to add the selected Ressources from this first listbox. Here is the first listbox :
final ListBox userRessourcesListBox = new ListBox(true);
Receiver<List<RessourceProxy>> receiver = new Receiver<List<RessourceProxy>>() {
#Override
public void onSuccess(List<RessourceProxy> response) {
for(RessourceProxy ressourceProxy : response) {
ressourcesListBox.addItem(ressourceProxy.getNom() + " " + ressourceProxy.getPrenom(), String.valueOf(ressourceProxy.getId()));
}
}
};
RessourceRequestContext request = requestFactory.ressourceRequestContext();
request.getAllRessource().fire(receiver);
So, as you can see, my code loops over the retrieved proxies from DB and initializes the items within the listbox.
Here are the control buttons :
final Button addButton = new Button(">");
addButton.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
for (int i = 0; i < ressourcesListBox.getItemCount(); i++) {
boolean foundInUserRessources = false;
if (ressourcesListBox.isItemSelected(i)) {
for (int j = 0; j < userRessourcesListBox
.getItemCount(); j++) {
if (ressourcesListBox.getValue(i).equals(
userRessourcesListBox.getValue(j)))
foundInUserRessources = true;
}
if (foundInUserRessources == false)
userRessourcesListBox.addItem(ressourcesListBox
.getItemText(i), ressourcesListBox
.getValue(i));
}
}
}
});
So when somebody selects one or more users and click on a ">" button, all the selected items go to the second listbox which is named userRessourceListBox
userRessourcesListBox.setWidth("350px");
userRessourcesListBox.setHeight("180px");
After that, I have a FINISH button, which loops over the items in the second listbox (which are the ones I have selected from the first one) and I try to make a request (again) with RequestFactory to retrieve the ressourceProxy object and initialize the userProxy ressources collection with the result
final Button nextButton = new Button("Finish");
nextButton.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
RessourceRequestContext request = requestFactory.ressourceRequestContext();
for(int i = 0; i < userRessourcesListBox.getItemCount(); i++) {
Receiver<RessourceProxy> receiver = new Receiver<RessourceProxy>() {
#Override
public void onSuccess(RessourceProxy response) {
userProxy.getRessource().add(response);
}
};
request.find(Long.parseLong(userRessourcesListBox.getValue(i))).fire(receiver);
}
creationRequest.save(newUserProxy).fire(new Receiver<Void>() {
#Override
public void onSuccess(Void response) {
Window.alert("Saved");
}
});
}
});
Finally, (in the code above) I try to save the UserProxy object (with the initial request context I have created userProxy with)... but it doesn't work
creationRequest.save(newUserProxy).fire(...)
It seems like when looping over the result in the onSuccess method :
userProxy.getRessource().add(response);
I retrieve the response (of type RessourceProxy) but beyond this method, for example when I try to save the userProxy object AFTER THE LOOP, there are no RessourceProxy objects in the ressourceProxy collection of userProxy...
Have you guys ever experienced something like this ?
Perhaps I am not doing it right : do I have to get the ressource with the UserRequestContext ? so that my newUser object and ressources are managed by the same request Context ?
if yes then I think it's a little bit weird to have something mixed together : I mean what is the benefit of having a Ressource-related operation in the User-related request context.
any help would be really really ... and I mean really appreciated ;-)
Thanks a lot
The message "… has been frozen" means that the object has been either edit()ed or passed as an argument to a service method, in another RequestContext instance (it doesn't matter whether it's of the same sub-type –i.e. UserRequestContext vs. RessourceRequestContext– or not) which hasn't yet been fire()d and/or the response has not yet come back from the server (or it came back with violations: when the receiver's onViolation is called, the objects are still editable, contrary to onSuccess and onFailure).
UPDATE: you have a race condition: you loop over the resource IDs and spawn as many requests as the number of items selected by the user, and then, without waiting for their response (remember: it's all asynchronous), you save the user proxy. As soon as you fire() that last request, the user proxy is no longer mutable (i.e. frozen).
IMO, you'd better keep the RessourceProxys retrieved initially and use them directly in the user proxy before saving it (i.e. no more find() request in the "finish" phase). Put them in a map by ID and get them from the map instead of finding them back from the server again.
I am writing Eclipse plugins, and frequently have a situation where a running Job needs to pause for a short while, run something asynchronously on the UI thread, and resume.
So my code usually looks something like:
Display display = Display.getDefault();
display.syncExec(new Runnable() {
public void run() {
// Do some calculation
// How do I return a value from here?
}
});
// I want to be able to use the calculation result here!
One way to do it is to have the entire Job class have some field. Another is to use a customized class (rather than anonymous for this and use its resulting data field, etc.
What's the best and most elegant approach?
I think the Container above is the "right" choice. It could be also be genericized for type safety. The quick choice in this kind of situation is the final array idiom. The trick is that a any local variables referenced from the Runnable must be final, and thus can't be modified. So instead, you use a single element array, where the array is final, but the element of the array can be modified:
final Object[] result = new Object[1];
Display display = Display.getDefault();
display.syncExec(new Runnable()
{
public void run()
{
result[0] = "foo";
}
}
System.out.println(result[0]);
Again, this is the "quick" solution for those cases where you have an anonymous class and you want to give it a place to stick a result without defining a specific Container class.
UPDATE
After I thought about this a bit, I realized this works fine for listener and visitor type usage where the callback is in the same thread. In this case, however, the Runnable executes in a different thread so you're not guaranteed to actually see the result after syncExec returns. The correct solution is to use an AtomicReference:
final AtomicReference<Object> result = new AtomicReference<Object>();
Display display = Display.getDefault();
display.syncExec(new Runnable()
{
public void run()
{
result.set("foo");
}
}
System.out.println(result.get());
Changes to the value of AtomicReference are guaranteed to be visible by all threads, just as if it were declared volatile. This is described in detail here.
You probably shouldn't be assuming that the async Runnable will have finished by the time the asyncExec call returns.
In which case, you're looking at pushing the result out into listeners/callbacks (possibly Command pattern), or if you do want to have the result available at a later in the same method, using something like a java.util.concurrent.Future.
Well, if it's sync you can just have a value holder of some kind external to the run() method.
The classic is:
final Container container = new Container();
Display display = Display.getDefault();
display.syncExec(new Runnable()
{
public void run()
{
container.setValue("foo");
}
}
System.out.println(container.getValue());
Where container is just:
public class Container {
private Object value;
public Object getValue() {
return value;
}
public void setValue(Object o) {
value = o;
}
}
This is of course hilarious and dodgy (even more dodgy is creating a new List and then setting and getting the 1st element) but the syncExec method blocks so nothing bad comes of it.
Except when someone comes back later and makes it asyncExec()..