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java - using XmlPullParser in annotation on Android

问题描述:

I'm trying to write an annotation processor that parses XML files and generates classes from them. The annotation is going to be used in an Android app, but my understanding is the annotation processor itself runs in the Java environment of the compiler. As such, I don't have access to the built-in Android XmlPullParser, so I've listed org.ogce:xpp3:1.1.6 as a dependency in my annotation processor's gradle file. My annotation processor is a separate module from the app (a Java Library module), in Android Studio. My app has a depends on this module.

This mostly works! My annotation processor runs and can successfully parse the XML. Unfortunately, I get this error when generating the APK for my android app:

trouble processing "javax/xml/namespace/QName.class":

Ill-advised or mistaken usage of a core class (java.* or javax.*)

when not building a core library.

This is often due to inadvertently including a core library file

in your application's project, when using an IDE (such as

Eclipse). If you are sure you're not intentionally defining a

core class, then this is the most likely explanation of what's

going on.

However, you might actually be trying to define a class in a core

namespace, the source of which you may have taken, for example,

from a non-Android virtual machine project. This will most

assuredly not work. At a minimum, it jeopardizes the

compatibility of your app with future versions of the platform.

It is also often of questionable legality.

If you really intend to build a core library -- which is only

appropriate as part of creating a full virtual machine

distribution, as opposed to compiling an application -- then use

the "--core-library" option to suppress this error message.

If you go ahead and use "--core-library" but are in fact

building an application, then be forewarned that your application

will still fail to build or run, at some point. Please be

prepared for angry customers who find, for example, that your

application ceases to function once they upgrade their operating

system. You will be to blame for this problem.

If you are legitimately using some code that happens to be in a

core package, then the easiest safe alternative you have is to

repackage that code. That is, move the classes in question into

your own package namespace. This means that they will never be in

conflict with core system classes. JarJar is a tool that may help

you in this endeavor. If you find that you cannot do this, then

that is an indication that the path you are on will ultimately

lead to pain, suffering, grief, and lamentation.

1 error; aborting

Error:Execution failed for task ':app:preDexDebug'.

> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_66.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1

I think, despite the unexpected class name in the error, that it doesn't like that I've included XmlPullParser in my app because it is provided by the system. So I did this in my app's gradle file to exclude it from the app's APK:

compile(project(':annotation-module')) {

exclude module: 'xpp3' // Android provides the XmlPull API so we can't include it

}

This results in a compile time exception from Javac when processing the annotation:

Error:Execution failed for task ':app:compileDebugJavaWithJavac'.

> java.lang.NoClassDefFoundError: org/xmlpull/v1/XmlPullParserException

I'm at a loss for how to resolve this. Is there no way I can include XPP in the Jar for my annotation processor but exclude it from the final APK? Is there some other approach I'm missing? I can't be the first person to try to parse XML in an annotation processor.

网友答案:

I think you might want to 'shadow' the XPP jar. Basically, you need to download the aar, extract out the jar file, then repackage it in a different namespace (with e.g. the shadow gradle plugin) and change your imports so they refer to the shadowed jar.

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