Android Studio + Gradle: java.lang.IllegalArgumentException

I have my project with Gradle and declare my dependencies on build.gradle:

dependencies {
compile 'com.android.support:support-v4:18.0.0'
compile 'org.springframework.android:spring-android-rest-template:1.0.1.RELEASE'
compile 'org.springframework.android:spring-android-auth:1.0.1.RELEASE'
compile 'org.springframework.android:spring-android-core:1.0.1.RELEASE'
compile 'org.roboguice:roboguice:2.0'

}

Build with Gradle work fine, but when a run my project a following error is throw on compilation phase:

Gradle: UNEXPECTED TOP-LEVEL EXCEPTION:
Gradle: java.lang.IllegalArgumentException: already added: Lorg/springframework/util/FileCopyUtils;
Gradle: at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:122)
Gradle: at com.android.dx.dex.file.DexFile.add(DexFile.java:161)

I use Gradle 1.8.

It looks like multiple libraries are including the core library files; I get a slightly different exception when I make a sample case, but it's the same cause. If I open up the External Libraries tab to look at what jars it's using, I see spring-android-core and spring-core, and if I open those up to see what classes are in them, I see that both contain org.springframework.core.ErrorCoded (which is the duplicate class in my test case).

You're not including spring-core directly; it's coming in as a transitive dependency from the spring-android-auth library (if I include just those two libraries and omit spring-android-rest-template I still get the error). I tried digging through the pom file definitions in Maven Central to try to prove why it's happening, but I'm not sure I could give you an explanation that didn't have a lot of holes in it, so I'll stay quiet on that front ;-) But I won't lack of understanding get in the way of trying to fix the problem. If you tell the spring-android-auth dependency to exclude spring-core, it does the trick:

dependencies {
    ...
    compile 'org.springframework.android:spring-android-rest-template:1.0.1.RELEASE'
    compile('org.springframework.android:spring-android-auth:1.0.1.RELEASE') {
        exclude module: 'spring-core'
    }
    compile 'org.springframework.android:spring-android-core:1.0.1.RELEASE'
}

I also came across this error:

Execution failed for task ':app:packageDebug'.
> Duplicate files copied in APK META-INF/notice.txt
File 1: /Users/sbarta/.gradle/caches/modules-2/files-2.1/org.springframework.android/spring-android-auth/1.0.1.RELEASE/f43faebbf90aef324979a81a4f5eee1e3b95191f/spring-android-auth-1.0.1.RELEASE.jar
File 2: /Users/sbarta/.gradle/caches/modules-2/files-2.1/org.springframework.android/spring-android-auth/1.0.1.RELEASE/f43faebbf90aef324979a81a4f5eee1e3b95191f/spring-android-auth-1.0.1.RELEASE.jar

so I had to follow the instructions at Android Gradle plugin 0.7.0: "duplicate files during packaging of APK" to exclude some META-INF/ files from packaging, and I added:

android {
    ...
    packagingOptions {
        exclude 'META-INF/notice.txt'
        exclude 'META-INF/license.txt'
    }
}