Java SE (Java Platform, Standard Edition)

Announcement

For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle.com. Technical questions should be asked in the appropriate category. Thank you!

Why does this select binding throw a NullPointerException?

ryan29Jan 24 2014 — edited Apr 8 2014

This should be pretty simple. The javadoc for Bindings#selectString says:

Creates a binding used to get a member, such as a.b.c. The value of the binding will be c, or "" if c could not be reached (due to b not having a c property, b being null, or c not being a String etc.).

Running this example:

import javafx.beans.binding.Bindings;
import javafx.beans.binding.StringBinding;
import javafx.beans.property.*;


public class SelectBindingExample {
    public static void main(String[] args) {
        ParentModel parentModel = new ParentModel();
        StringBinding bindingA = createBinding(parentModel);
        String nameA = bindingA.get(); // NPE while evaluating
        System.out.println("Bound value is " + (nameA != null ? nameA : "null") + ".");


        parentModel.setChildModel(new ChildModel());
        StringBinding bindingB = createBinding(parentModel);
        String nameB = bindingB.get();
        System.out.println("Bound value is " + (nameB != null ? nameB : "null") + ".");
    }


    private static StringBinding createBinding(ParentModel parentModel) {
        return Bindings.selectString(parentModel.childModelProperty(), "name");
    }


    public static class ParentModel {
        private final ObjectProperty<ChildModel> childModel = new SimpleObjectProperty<>();
        public final ReadOnlyObjectProperty<ChildModel> childModelProperty() {return childModel;}
        public final ChildModel getChildModel() {return childModel.get();}
        public final void setChildModel(ChildModel childModel) {this.childModel.set(childModel);}
    }


    public static class ChildModel {
        private final StringProperty name = new SimpleStringProperty("Child Model Name");
        public final ReadOnlyStringProperty nameProperty() {return name;}
        public final String getName() {return name.get();}
        protected final void setName(String name) {this.name.set(name);}
    }
}

..causes a NPE while evaluating the binding:

WARNING: Exception while evaluating select-binding [name]

Jan 24, 2014 7:10:57 AM com.sun.javafx.binding.SelectBinding$SelectBindingHelper getObservableValue

INFO: Property 'name' in ReadOnlyObjectProperty [bean: SelectBindingExample$ParentModel@4437c4, name: childModel, value: null] is null

java.lang.NullPointerException

at com.sun.javafx.binding.SelectBinding$SelectBindingHelper.getObservableValue(SelectBinding.java:481)

at com.sun.javafx.binding.SelectBinding$AsString.computeValue(SelectBinding.java:394)

at javafx.beans.binding.StringBinding.get(StringBinding.java:152)

at SelectBindingExample.main(SelectBindingExample.java:9)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:483)

at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

What's going wrong here? I've updated the example to work with the Bindings#selectString method from Java 7 and things work as expected. Is this a bug?

Slight modification to the example so it works with Java 7.

This post has been answered by James_D on Jan 24 2014

Jump to Answer

AlbertoFaenza

Hi,

welcome to the forum.

Please read 2176552

How do you pretend to get an answer with such questions?
Where is your table structure?
Where is your sample data?

Regards.
Al

L-MachineGun

Also, be aware we DO NOT do the homework for you but rather may help you if you get "stuck".
You need to work it out yourself and post the results.
:p

sb92075

Handle: 945059
Status Level: Newbie
Registered: Jul 8, 2012
Total Posts: 213
Total Questions: 42 (34 unresolved)

why do you waste time here when most of your questions remain unanswered?

APC

The one thing more annoying than people who post code without using the {noformat}

{noformat} tag to make it readable and those people who use {noformat}

{noformat} tags to render ordinary text unreadable.

You have posted more than two hundred times. That really ought to be sufficient both to understand how to use the forum software properly and to grasp the etiquette of asking your questions in an appropriate way.

So please edit your question and fix the formatting.

Your future co-operation is appreciated.

Cheers, APC

stefan nebesnak

Could you post the schema of these tables?

SQL*Plus command:
 
SQL> DESC TIS_EVENT
SQL> DESC TIS_DT
SQL> DESC TIS_EVENT_DT_RLTSHP

Your requirement is very unclear, it's difficult to suggest the correct way, check the following example:

SELECT t.r_id_event4, 
       t.event_id, 
       t2.event_desc, 
       To_char(t3.DATE, 'YYYY') AS Year 
FROM   tis_event_dt_rltshp t --EVENT DATE RELATIONSHIP 
       join tis_event t2 USING (event_id) --EVENT 
       join tis_dt t3 USING (event_id) --DATE 
WHERE  t2.annual_event_flg = 'Y' 
       AND To_char(t3.DATE, 'YYYY') = '2013';

1 - 5

Locked Post

New comments cannot be posted to this locked post.

Locked on May 6 2014

Added on Jan 24 2014

#javafx-2-0-and-later

7 comments

6,113 views

Java SE (Java Platform, Standard Edition)

Why does this select binding throw a NullPointerException?

Comments

Post Details