如果在jsoup中定义了元素，分配给变量的最干净方法是？

Question

I was doing this String name = doc.select("h1#name").first().text(); and I received a NullPointerException on a page where the 'h1#name' element did not exist. I'm parsing the DOM, grabbing hundreds of elements. It seems that I need to test each element before I assign, so I changed it to this:

String name = null;

if( doc.select("h1#name").first() != null && doc.select("h1#name").first().text() != null ))
    name = doc.select("h1#name").first.text();

Is there a better way to do it? I'm just learning Java, and my background is in Perl, where I'd do something like this:

my $name = $doc->select("h1#name")->text if $doc->select("h1#name");

It's not a big deal, since my code does work for me. I was just wondering if there was a cleaner way to do this in Java.

Answer 1

You will not come arround checking all objects you go throuth to access the value you want.

To translate your perl syntax into java I would use the ternary operator :

name = doc.select("h1#name").first() != null ? 
            doc.select("h1#name").first().text() : null

There is no need to check doc.select("h1#name).first().text() != null too unless you have a non null value in name and you don't want to override it with null.

Answer 2

I would suggest a utility method, something like this:

Document mDocument;

(...)

String getElementTextOrNull (String cssQuery) {
    Element e = mDocument.select(cssQuery).first();

    if (e == null) {
        return null;
    } else {
        return e.text();
    }
}

Then, you can eliminate a lot of boilerplate and repetition, so your code simply becomes:

String name = getElementTextOrNull("h1#name");

You can also do other things in that method, like checking if the text is empty or if it is valid.

Of course, this may be impractical if you only get the text of a specific element once, but this is what I would suggest otherwise. Personally, I also think this is neater and more concise than the ternary operator solution proposed in the other answer.