Android: XmlPullParserFactory.newInstance() creating a null factory

Question

I'm trying to get XmlPullParser working as it makes a lot more sense than the alternatives. However I'm falling at the first hurdle as the XmlPullParserFactory.newInstance() function is returning a null factory (seen by the debugger). Thus an exception is raised as soon as factory.newPullParser() is called.

import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;

public class XMLParser
{
    public static void getXML(InputStream in)
            throws XmlPullParserException, IOException {
        try {
            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser xpp = factory.newPullParser();

            xpp.setInput(new StringReader("<foo>Hello World!</foo>"));
            int eventType = xpp.getEventType();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                if (eventType == XmlPullParser.START_DOCUMENT) {
                    System.out.println("Start document");
                } else if (eventType == XmlPullParser.START_TAG) {
                    System.out.println("Start tag " + xpp.getName());
                } else if (eventType == XmlPullParser.END_TAG) {
                    System.out.println("End tag " + xpp.getName());
                } else if (eventType == XmlPullParser.TEXT) {
                    System.out.println("Text " + xpp.getText());
                }
                eventType = xpp.next();
            }
            System.out.println("End document");
        } catch (Exception e) {
        }
    }
}

I'm calling this method from a Unit Test. I'm really stumped as to what the issue could be as I've not found any posts that have had issues like this.

Trace report: Full thread dump

"main@1" prio=5 tid=0x1 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
  at com.company.app.XMLParser.getXmln(XMLParser.java:40)
  at com.company.app.XMLParserTest.setUp(XMLParserTest.java:36)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-1)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:497)
  at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
  at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
  at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
  at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
  at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
  at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
  at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
  at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
  at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
  at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
  at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
  at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:78)
  at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:212)
  at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)

"Finalizer@836" daemon prio=8 tid=0x3 nid=NA waiting
  java.lang.Thread.State: WAITING
  at java.lang.Object.wait(Object.java:-1)
  at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
  at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
  at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)

"Reference Handler@837" daemon prio=10 tid=0x2 nid=NA waiting
  java.lang.Thread.State: WAITING
  at java.lang.Object.wait(Object.java:-1)
  at java.lang.Object.wait(Object.java:502)
  at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157)

"Attach Listener@834" daemon prio=5 tid=0x5 nid=NA runnable
  java.lang.Thread.State: RUNNABLE

"Signal Dispatcher@835" daemon prio=9 tid=0x4 nid=NA runnable
  java.lang.Thread.State: RUNNABLE

Gearwheel

It's just returning a newly created instance; no chance of getting null there . Please add Log.wtf("PullParser", e) to your catch clause and post the results. – Elbert

The exception being reported is a NullPointerException. – Gearwheel

Added a trace report to my question. Hopefully its what you are after. – Gearwheel

I was after the stack-trace you find in LogCat when logging the exception like I proposed. Not the whole thread-dump which doesn't anything about the exception itself. – Elbert

Tried running it on device and it seems to work correctly. The issue must have something to do with XmlPullParser not working from Unit Tests? – Gearwheel

Answer 1

You cannot unit test components of Android. The JAR file used for compilation only contains method stubs throwing exceptions. Consider a simple test case for your issue

public class UnitTest {
    @Test
    public void instanceNotNull() throws Exception {
        assertNotNull(XmlPullParserFactory.newInstance());
    }
}

Running it without any configuration defined, you'll get a

java.lang.RuntimeException: Method newInstance in org.xmlpull.v1.XmlPullParserFactory not mocked. See http://g.co/androidstudio/not-mocked for details.
    at org.xmlpull.v1.XmlPullParserFactory.newInstance(XmlPullParserFactory.java)
    at ...

When adding

testOptions {
    unitTests.returnDefaultValues = true
}

to your gradle android configuration, you'll find the test just fail on the assertion.

If you want to test with the android library, you need to do it on a device with an instrumented test. So put your test case in the androidTest source set, add

dependencies {
    testCompile 'junit:junit:4.12'
    androidTestCompile 'com.android.support.test:runner:0.4'
}

to the gradle file of your module and run it on a device.

For more information see Testing Concepts and Testing Support Library.

Elbert

Answer 2

Just add this line to your wish list

                (new Thread() {
                    @Override
                    public void run() {
                        try {
                            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
                            XmlPullParser xpp = factory.newPullParser();

                            xpp.setInput(new StringReader("<foo>Hello World!</foo>"));
                            int eventType = xpp.getEventType();
                            while (eventType != XmlPullParser.END_DOCUMENT) {
                                if (eventType == XmlPullParser.START_DOCUMENT) {
                                    System.out.println("Start document");
                                } else if (eventType == XmlPullParser.START_TAG) {
                                    System.out.println("Start tag " + xpp.getName());
                                } else if (eventType == XmlPullParser.END_TAG) {
                                    System.out.println("End tag " + xpp.getName());
                                } else if (eventType == XmlPullParser.TEXT) {
                                    System.out.println("Text " + xpp.getText());
                                }
                                eventType = xpp.next();
                            }
                            System.out.println("End document");
                        } catch (Exception e) {
                        }
                    }
                }
                ).start();

Jacobinism