Why I get NullPointerException when running StAX Parser?

Question

I\'m trying to write a StAX XML Parser in Java, but always get NullPointerException error. Please help me to solve this issue. Full problem:

Exception in thr

Answer 1

UPDATED: Comment to original answer:

It doesn't work, it gives the same error

That means the problem is because the shoes variable is null, as would have easily been seen with a debugger. Using a debugger would have saved us all a lot of time, so please start using one.

In order for shoes to be null, it appears that the code encountered a <title> element that is not a child of a Shoes element.

To fix the code, add a null-check, and also set shoes = null at the end of processing the Shoes element:

} else if (startElement.getName().getLocalPart().equals("title")) {
    if (shoes != null) { // <===== ADD THIS
        shoes.setTitle(reader.getElementText()); // <===== Fix this (see original answer)
    }

if (xmlEvent.isEndElement()) {
    EndElement endElement = xmlEvent.asEndElement();
    if (endElement.getName().getLocalPart().equals("Shoes")) {
        shoesList.add(shoes);
        shoes = null; // <===== ADD THIS
    }
}

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ORIGINAL ANSWER

Your code is:

} else if (startElement.getName().getLocalPart().equals("title")){
    xmlEvent = reader.nextEvent();
    shoes.setTitle(xmlEvent.asCharacters().getData());

The problem is that the code isn't checking what type if event follows the START_ELEMENT event. It could be that:

• Most likely, the element is empty, i.e. <title/> or <title><title/>, in which case the next event is an END_ELEMENT, and asCharacters() returned null.

• The element has a comment, e.g. <title><!-- there is no title --><title/>, in which case the next event is a COMMENT.

• The element has mixed content, e.g. <title>foo<![CDATA[bar]]><title/>, in which case the next event is not the full text.

Retrieving the text content of an element is such a common thing that they added a helper method for that: getElementText():

Reads the content of a text-only element. Precondition: the current event is START_ELEMENT. Postcondition: The current event is the corresponding END_ELEMENT.

Throws:
XMLStreamException - if the current event is not a START_ELEMENT or if a non text element is encountered

Which means that your code should be:

} else if (startElement.getName().getLocalPart().equals("title")) {
    shoes.setTitle(reader.getElementText());