Question

I always thought that newlines and whitespace in XML documents were ignored ? Is that a misconception, or is there something lacking in my code?

What happens is the following: I’m parsing an XML document which I retrieve from my server. This works fine when all content is on 1 line, but fails when the XML document is indented.

My code :

public class JsonTestActivity extends ListActivity {
    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

       Log.d("xxx", "on create started");
        try {
            URL url = new URL("http://www.morefast.be/gethistory.php");

            HttpURLConnection urlConnection=(HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.setDoOutput(true);
            urlConnection.setDoInput(true);
            urlConnection.connect();

            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document doc = db.parse(urlConnection.getInputStream());        

            String path = doc.getElementsByTagName("GeometryCollection").item(0).getFirstChild().getFirstChild().getFirstChild().getNodeValue() ;

            Log.d("xxx", "path is "+path);

        }
        catch (Exception e) {
            Log.d("xxx", e.getMessage());

        }



    }



}

Works fine when the XML file is

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0"><Document>
<GeometryCollection><LineString><coordinates>These are the coordinates</coordinates></LineString></GeometryCollection>
</Document></kml>

But fails when the file is (e.g.)

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0"><Document>
<GeometryCollection>
<LineString><coordinates>These are the coordinates</coordinates></LineString></GeometryCollection>
</Document></kml>

All I changed in those files is adding an extra newline after “GeometryCollection”

LogCat shows

07-30 20:44:48.364: ERROR/AndroidRuntime(545): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mydomain.jsontest/com.mydomain.jsontest.JsonTestActivity}: java.lang.NullPointerException: println needs a message
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.os.Looper.loop(Looper.java:123)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread.main(ActivityThread.java:4627)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at java.lang.reflect.Method.invokeNative(Native Method)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at java.lang.reflect.Method.invoke(Method.java:521)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at dalvik.system.NativeStart.main(Native Method)
07-30 20:44:48.364: ERROR/AndroidRuntime(545): Caused by: java.lang.NullPointerException: println needs a message
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.util.Log.println_native(Native Method)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.util.Log.d(Log.java:122)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at com.mydomain.jsontest.JsonTestActivity.onCreate(JsonTestActivity.java:43)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
07-30 20:44:48.364: ERROR/AndroidRuntime(545):     ... 11 more

Is that expected? I’d thought that XML documents ignored whitespace?

Answer 1

Disclaimer: I don’t do Android (or even Java these days) programming, however…

---

White-space in XML is generally not ignored by the parser. Rather it is turned into text nodes (containing the white-space as content). The exact details depends on the XML parser and options
supplied.

Could this be changing what getFirstChild() is doing? That is, is the first child of GeometryCollection a text node and not LineString? (And the first child of a text node is …? Kaboom! Although, I can’t fit this into the trace: java.lang.NullPointerException: println needs a message… which seems odd sitting there.)

I would suggest starting with a better selector and avoiding the manual stepping, if this is indeed the case.

Happy coding.