UnmarshalException caused by NullPointerException - exception

Question

I'm working on an application and I need to save and load data from an ObservableArrayList to an XML file. I've made a model class with Double and Integer Properties for the ObservableList:
package application.Model;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.SimpleIntegerProperty;
#XmlRootElement
#XmlType(name = "Object", propOrder = {"diameter", "handeling", "aantal", "basisUren", "correctie", "toeslagUren", "totaalUren", "totaalMat", "totaal"})
public class Berekening {
private final SimpleIntegerProperty diameter;
private final SimpleIntegerProperty handeling;
private final SimpleIntegerProperty aantal;
private final SimpleDoubleProperty basisUren;
private final SimpleDoubleProperty correctie;
private final SimpleDoubleProperty toeslagUren;
private final SimpleDoubleProperty totaalUren;
private final SimpleDoubleProperty totaalMat;
private final SimpleDoubleProperty totaal;
public Berekening() {
this(null, null, null, null, null, null, null, null, null);
}
public Berekening(Integer diameter, Integer handeling, Integer aantal, Double basisUren, Double correctie, Double toeslagUren, Double totaalUren, Double totaalMat, Double totaal) {
this.diameter = new SimpleIntegerProperty(diameter);
this.handeling = new SimpleIntegerProperty(handeling);
this.aantal = new SimpleIntegerProperty(aantal);
this.basisUren = new SimpleDoubleProperty(basisUren);
this.correctie = new SimpleDoubleProperty(correctie);
this.toeslagUren = new SimpleDoubleProperty(toeslagUren);
this.totaalUren = new SimpleDoubleProperty(totaalUren);
this.totaalMat = new SimpleDoubleProperty(totaalMat);
this.totaal = new SimpleDoubleProperty(totaal);
}
#XmlElement (name = "value1", required = false)
public Integer getDiameter() {
return diameter.get();
}
public void setDiameter(int diameter) {
this.diameter.set(diameter);
}
public IntegerProperty diameterProperty(){
return diameter;
}
#XmlElement (name = "value2", required = false)
public Integer getHandeling() {
return handeling.get();
}
public void setHandeling(int handeling) {
this.handeling.set(handeling);
}
public IntegerProperty handelingProperty(){
return handeling;
}
#XmlElement (name = "value3", required = false)
public Integer getAantal() {
return aantal.get();
}
public void setAantal(int aantal) {
this.aantal.set(aantal);
}
public IntegerProperty aantalProperty(){
return aantal;
}
#XmlElement (name = "value4", required = false)
public Double getBasisUren(){
return basisUren.get();
}
public void setBasisUren(double value) {
this.basisUren.set(value);
}
public DoubleProperty basisUrenProperty(){
return basisUren;
}
#XmlElement (name = "value5", required = false)
public Double getCorrectie(){
return correctie.get();
}
public void setCorrectie(double value) {
this.correctie.set(value);
}
public DoubleProperty correctieProperty(){
return correctie;
}
#XmlElement (name = "value6", required = false)
public Double getToeslagUren(){
return toeslagUren.get();
}
public void setToeslagUren(double value) {
this.toeslagUren.set(value);
}
public DoubleProperty toeslagUrenProperty(){
return toeslagUren;
}
#XmlElement (name = "value7", required = false)
public Double getTotaalUren(){
return totaalUren.get();
}
public void setTotaalUren(double value) {
this.totaalUren.set(value);
}
public DoubleProperty totaalUrenProperty(){
return totaalUren;
}
#XmlElement (name = "value8", required = false)
public Double getTotaalMat(){
return totaalMat.get();
}
public void setTotaalMat(double value) {
this.totaalMat.set(value);
}
public DoubleProperty totaalMatProperty(){
return totaalMat;
}
#XmlElement (name = "value9", required = false)
public Double getTotaal(){
return totaal.get();
}
public void setTotaal(double value) {
this.totaal.set(value);
}
public DoubleProperty totaalProperty(){
return totaal;
}
}
This is the list class:
package application.Model;
import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlElement;
public class BerekeningList {
#XmlElement(name = "berekening")
List<Berekening> berekeningen = new ArrayList<>();
public List<Berekening> getBerekeningen() {
return berekeningen;
}
}
And the ListWrapper:
package application.Model;
import java.util.List;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import application.MainApp;
import application.Util.BerekeningListAdapter;
import javafx.collections.ObservableList;
#XmlRootElement (name = "Berekeningen")
public class BerekeningListWrapper{
private ObservableList<Berekening> berekening;
#XmlJavaTypeAdapter(BerekeningListAdapter.class)
public ObservableList<Berekening> getBerekeningen(){
return berekening;
}
public void setBerekenings(ObservableList<Berekening> berekenings) {
this.berekening = berekenings;
}
}
I use this method to Save the data to a file:
public void saveBerekeningDataToFile(File file) {
try {
JAXBContext context = JAXBContext
.newInstance(BerekeningListWrapper.class);
Marshaller m = context.createMarshaller();
m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
BerekeningListWrapper wrapper = new BerekeningListWrapper();
wrapper.setBerekenings(berekeningData);
m.marshal(wrapper, file);
setBerekeningFilePath(file);
} catch (Exception e) {
Alert alert = new Alert(AlertType.ERROR);
alert.setTitle("Error");
alert.setHeaderText("Could not save data");
alert.setContentText("Could not save data to file:\n" + file.getPath());
alert.showAndWait();
}
}
And the resulting xml file (the saving seems to work fine):
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Berekeningen>
<berekeningen>
<berekening value1="15" value2="5" value3="5" value4="1.25" value5="5.0" value6="6.25" value7="270.0" value8="30.0" value9="300.0"/>
</berekeningen>
The issue is loading the data back into my application, i'm using this method:
public void loadBerekeningDataFromFile(File file){
try {
JAXBContext context = JAXBContext
.newInstance(BerekeningListWrapper.class);
Unmarshaller um = context.createUnmarshaller();
BerekeningListWrapper wrapper = (BerekeningListWrapper)um.unmarshal(file);
berekeningData.clear();
berekeningData.addAll(wrapper.getBerekeningen());
setBerekeningFilePath(file);
} catch (Exception e){
e.printStackTrace();
Alert alert = new Alert(AlertType.ERROR);
alert.setTitle("Error");
alert.setHeaderText("Could not load data");
alert.setContentText("Could not load data from file:\n" + file.getPath());
alert.showAndWait();
}
}
Resulting in a stack trace starting with:
javax.xml.bind.UnmarshalException: Unable to create an instance of
application.Model.Berekening
etc
Caused by: java.lang.NullPointerException
at application.Model.Berekening.<init>(Berekening.java:32)
at application.Model.Berekening.<init>(Berekening.java:28)
... 84 more
So the unmarshalexception is caused by a NullPointerException in my model class at the lines:
this.diameter = new SimpleIntegerProperty(diameter);
and
this(null, null, null, null, null, null, null, null, null);
I don't know how I can resolve this issue, I've tried out many different tutorials and answers on StackOverflow, but nothing I found neems to work.
Any help is much appreciated!

Answer 1

You can't initialize a SimpleIntegerProperty with null. The constructor you are calling takes an int, so there is an implicit call ("unboxing") to diameter.intValue() when you call new SimpleIntegerProperty(diameter). Obviously, if diameter is null, this results in a NullPointerException.
Make the default values for the numeric types non-null:
public Berekening() {
this(0, 0, 0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
}
for example.
If you really need to support null values (and this is a less-preferred option, imho) use ObjectProperty instead of IntegerProperty and DoubleProperty:
public class Berekening {
private final ObjectProperty<Integer> diameter;
private final ObjectProperty<Integer> handeling;
private final ObjectProperty<Integer> aantal;
private final ObjectProperty<Double> basisUren;
private final ObjectProperty<Double> correctie;
private final ObjectProperty<Double> toeslagUren;
private final ObjectProperty<Double> totaalUren;
private final ObjectProperty<Double> totaalMat;
private final ObjectProperty<Double> totaal;
public Berekening() {
this(null, null, null, null, null, null, null, null, null);
}
public Berekening(Integer diameter, Integer handeling, Integer aantal, Double basisUren, Double correctie, Double toeslagUren, Double totaalUren, Double totaalMat, Double totaal) {
this.diameter = new SimpleObjectProperty<>(diameter);
this.handeling = new SimpleObjectProperty<>(handeling);
this.aantal = new SimpleObjectProperty<>(aantal);
this.basisUren = new SimpleObjectProperty<>(basisUren);
this.correctie = new SimpleObjectProperty<>(correctie);
this.toeslagUren = new SimpleObjectProperty<>(toeslagUren);
this.totaalUren = new SimpleObjectProperty<>(totaalUren);
this.totaalMat = new SimpleObjectProperty<>(totaalMat);
this.totaal = new SimpleObjectProperty<>(totaal);
}
// ...
}