Woodstox on Android

Question

I've previously written a library in Java using the native Java 1.6 Stax parser heavily. However, I now want use this library for Android, meaning that this parser is not supported. I'd like to use Woodstox as it implements the Stax 1.0 api and I wouldn't have to rewrite any of my current code, just sub in the dependency.

Android does not have the stax 1 api, so I realize I have to add it. Right now, I've added the woodstox-core-asl-4.2.0.jar, stax-api-1.0-2.jar, and the stax2-api-3.1.3.jar to the classpath. Everything compiles fine, but when I actually try to run an Android application which depends on this library, I get runtime errors indicating it isn't using Woodstox as the implementation for the stax 1 api.

Is there something I'm misunderstanding or doing incorrectly? Am I missing a jar? I've read the Woodstox help page thoroughly but can't find anything else I'm missing.

EDIT: I'm starting to wonder if it's actually possible to use Woodstox on Android. The issue is with the dependency on the stax api. After some research I discovered that the Dalvik VM appears to not be ok with those packages being in the javax.* namespace.

Answer 1

How are you passing XMLInputFactory / XMLOutputFactory instance? Usually it is better to directly construct instances (of WstxInputFactory, WstxOutputFactory), since there is no real benefit from callign XMLInputFactory.newInstance(): at most it adds overhead (much slower, scans classpath).

You are not missing any jars: core and stax2-api are needed always; and if the platform does not include Stax API jar (which Android for some odd reason does not, even tho it is part of JDK 1.6), then that one.

EDIT:

Auto-discovery should be based on couple of things:

1. XMLInputFactory (etc) check to see if matching system property ("javax.xml.stream.XMLInputFactory") has value; this is class name of factory to use, if any. So you can set system property with specific impl value
2. If no system property found, see if there is resource META-INF/services/javax.xml.stream.XMLInputFactory to read; one line with class name
3. If neither works, try to create default instance; for J2SE SDK this would be implementation that Oracle provides (Sjsxp)

Woodstox provides SPI information (step 2), to auto-register itself. But since on Android you repackage jars (as Android packages, APK?), it is possible that resource files are either not included, or not found. If this is the root cause, you can still set matching system property. If not, you will need to provide class name or factory instance using other means.