9 replies to this topic

[dlinx90]

My hibernate mapping requires me to make a custom PropertyEditor for converting a String into an Object type (Document). The setAsText method is working fine and I'm able to save a document number to the database but when I try to display the document number it displays what i believe is an object address (testapp.domain.Document@eeccff..or something similar). When I add a getAsText method to the PropertyEditor it gives me the following error:

java.lang.NullPointerException
testapp.controller.DocumentRevisionController$DocumentPropertyEditor.getAsText(DocumentRevisionController.java:59)

Mapping:

    @OneToMany(mappedBy="document_number", cascade = CascadeType.ALL)
private Set<DocumentRevision> documentRevisions;

public void setDocumentRevisions(Set<DocumentRevision> documentRevisions){
    this.documentRevisions = documentRevisions;
}

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name="DOCUMENT_NUMBER")
private Document document_number; 

public void setDocument_number(Document document_number){
    this.document_number = document_number;
}

public Document getDocument_number(){
    return document_number;
}

part of the Controller:

 class DocumentPropertyEditor extends PropertyEditorSupport {

    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        Document value =  documentService.retrieveDocumentNumber(text);
        setValue(value);
    }

    @Override
    public String getAsText() {
        Document d = (Document) getValue();
        return d != null ? String.valueOf(d.getDocumentNumber()) : "";
    }

}


@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.registerCustomEditor(Document.class, new DocumentPropertyEditor());
}


@RequestMapping(value="/add", method=RequestMethod.GET)
public String getDocumentRevision(Model model) {
DocumentRevision documentRevision = new DocumentRevision();
model.addAttribute("documentRevisionAttribute", documentRevision);
model.addAttribute("documentNumberList", documentService.retrieveAllDocumentNumbers());

return "new-documnent-revision";
}


@RequestMapping(value="/add", method=RequestMethod.POST)
public String postDocumentRevision(@ModelAttribute("documentRevisionAttribute") @Valid DocumentRevision documentRevision, BindingResult result) {

if(result.hasErrors()){
    return "new-document-revision";
}

documentRevisionService.createDocumentRevision(documentRevision);
return "redirect:/testapp/document-revision/list";  
}

Method that retrieves DocumentNumbers:

public void saveDocumentRevision(DocumentRevision documentRevision) {
    this.sessionFactory.getCurrentSession().save(documentRevision); 
}

Can anyone see where I've made a mistake and why the getAsText method gives the exception? Thank you for your help!

/D

[Norm]

what variable on line 59 has a null value? Find that variable and then find out why it does not have a valid non-null value.

[dlinx90]

what variable on line 59 has a null value? Find that variable and then find out why it does not have a valid non-null value.

It's this line:

return d != null ? String.valueOf(d.getDocumentNumber()) : "";

I'm guessing it's the "d" variable that has null value although I don't understand why. Does anyone know?

[wim DC]

d most likely is not null, but d.getDocumentNumber() returns null

[dlinx90]

After adding this to the getAsText method it resolves the nullpointerexception:

	  if(getValue() == null){
    return null;
   }

But my problem is now how to be able to display the documentNumber as a String when I display the documentRevision table. Now it gets displayed as: testapp.domain.Document@1f93466.
What can i do to resolve this issue?

[wim DC]

toString method of Document?

[Norm]

testapp.domain.Document@1f93466.

That's the value returned by the default toString() method. Add a toString() method to the Document class that returns the String you want to see printed.

[dlinx90]

That's the value returned by the default toString() method. Add a toString() method to the Document class that returns the String you want to see printed.

If I add toString to the getDocumentNumber method in the Document.java as such:

public String getDocumentNumber(){
		return documentNumber.toString();
	}

then i get the following error:

org.springframework.beans.InvalidPropertyException: Invalid property 'documentNumber' of bean class [testapp.domain.Document]: Getter for property 'documentNumber' threw exception; nested exception is java.lang.reflect.InvocationTargetException

And i cant add it to the getter in the DocumentRevision.java since it needs to return a Document type.

How should i do it?

[wim DC]

He meant you need to add a whole new method:

@Override
public String toString() {
   return "whatever you want it to show";
}

That's pretty basic Java. How did you get this far in hibernate and Spring without knowing the basics.

[dlinx90]

Thanks that works!

That's pretty basic Java. How did you get this far in hibernate and Spring without knowing the basics.

Google.