CODEWITHSUNDEEP
wicket
maxko87
maxko87

Reputation: 2940

Attempt to set model object on null model of component: form:checkgroup

I'm trying to create a list of HITs (objects), where each has a checkbox next to it, so that I can select them and delete them all at once. I've made a form with a checkbox for each row in the table:

 final HashSet<HIT> selectedValues = new HashSet<HIT>(); 

 final CheckGroup checkgroup = new CheckGroup("checkgroup");

 final Form form = new Form("form"){
        @Override
        public void onSubmit() {
            super.onSubmit(); 
        }
    };

    checkgroup.add(new CheckGroupSelector("checkboxSelectAll"));

    UserHitDataProvider userHitDataProvider = new UserHitDataProvider(selectedIsReal, keyId, secretId);

    final DataView<HIT> dataView = new DataView<HIT>("pageable", userHitDataProvider) {
        private static final long serialVersionUID = 1L;

        @Override
        protected void populateItem(final Item<HIT> item) {
            HIT hit = item.getModelObject();
            item.add(new CheckBox("checkbox", new SelectItemUsingCheckboxModel(hit,selectedValues))); 

            item.add(new Label("hitName", String.valueOf(hit.getTitle())));
            item.add(new Label("hitId", String.valueOf(hit.getHITId())));
        }
    };

//add checkgroup to form, form to page, etc.

I've also added a new class to take care of the selection/deletion:

public class SelectItemUsingCheckboxModel extends AbstractCheckBoxModel {

private HIT hit; 
private Set selection; 

public SelectItemUsingCheckboxModel(HIT h, Set selection) { 
    this.hit = h; 
    this.selection = selection; 
 } 

@Override 
public boolean isSelected() { 
    return selection.contains(hit); 
} 

@Override 
public void select() { 
    selection.add(hit); 
} 

@Override 
public void unselect() { 
    selection.remove(hit); 
}

}

Everything renders fine, but I get an error when trying to submit:

Caused by: java.lang.IllegalStateException: Attempt to set model object on null model of component: form:checkgroup
at org.apache.wicket.Component.setDefaultModelObject(Component.java:3042)
at org.apache.wicket.markup.html.form.FormComponent.updateCollectionModel(FormComponent.java:1572)
at org.apache.wicket.markup.html.form.CheckGroup.updateModel(CheckGroup.java:160)
at org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:228)
at org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:198)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:274)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrder(Visits.java:245)
at org.apache.wicket.markup.html.form.FormComponent.visitComponentsPostOrder(FormComponent.java:422)
at org.apache.wicket.markup.html.form.Form.internalUpdateFormComponentModels(Form.java:1793)
at org.apache.wicket.markup.html.form.Form.updateFormComponentModels(Form.java:1757)
at org.apache.wicket.markup.html.form.Form.process(Form.java:913)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:770)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:703)
... 27 more

I think its some of the Ajax code breaking, since my SelectAllCheckBox button is also failing. Any ideas why? Is this even the best way to handle such a use case?

Upvotes: 0

Views: 4326

Answers (1)

Cedric Gatay
Cedric Gatay

Reputation: 1583

Your Checkgroup does not have a Model, thus Wicket can't copy the current state of the Model into a null object. You should use the constructor with an additional parameter representing the Model you want to store the value in.

Upvotes: 1

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