java.lang.IllegalArgumentException: already added: Lorg/hamcrest/BaseDescription; Conversion to Dalvik format failed with error 1

Question

First of all, there are at least 2 postings with the same problem but these solutions don't work anymore, at least not in my installation.

I'm using m2e with Eclipse and Android and tried to run the application as "Android Application" by selecting run as->Android application, but I always get this error:

UNEXPECTED TOP-LEVEL EXCEPTION: java.lang.IllegalArgumentException: already added: Lorg/hamcrest/BaseDescription;
. . .

[2012-09-08 19:50:41 - net.mydomain.project-TRUNK] Conversion to Dalvik format failed with error 1

It's the problem described here in Tools R14 section. First of all, this cannot be fixed because I have this issue in ADT 20.0.3. Secondly, I don't have these so called "_src" folders. I've never seen them in a Maven project before, so I don't know what I should do now. I don't even have any libraries linked twice. At least I don't see some in my project. Any ideas how to get this working?

Here is my pom.xml if this helps:

<?xml version="1.0" encoding="UTF-8"?>
  <project xmlns="http://maven.apache.org/POM/4.0.0"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven- v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.devgems.android</groupId>
    <artifactId>kurzparkzonewien</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>apk</packaging>
    <name>kurzparkzonewien</name>

    <properties>
        <platform.version>1.6_r2</platform.version>
        <android.sdk.path>/opt/android-sdk-linux</android.sdk.path>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.google.android</groupId>
            <artifactId>android</artifactId>
            <version>${platform.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>com.googlecode.json-simple</groupId>
            <artifactId>json-simple</artifactId>
            <version>1.1.1</version>
        </dependency>

        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.0.1</version>
        </dependency>
        <!-- Make sure this is below the android dependencies -->
        <dependency>
            <groupId>com.pivotallabs</groupId>
            <artifactId>robolectric</artifactId>
            <version>1.0-RC1</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <outputDirectory>target/classes</outputDirectory>
        <testOutputDirectory>target/test-classes</testOutputDirectory>

        <plugins>
            <plugin>
                 <groupId>com.jayway.maven.plugins.android.generation2</groupId>
                <artifactId>android-maven-plugin</artifactId>
                <version>3.1.1</version>
                <configuration>
                    <androidManifestFile>${project.basedir}/AndroidManifest.xml</androidManifestFile>
                    <assetsDirectory>${project.basedir}/assets</assetsDirectory>
                    <resourceDirectory>${project.basedir}/res</resourceDirectory>
                    <nativeLibrariesDirectory>${project.basedir}/src/main/native</nativeLibrariesDirectory>
                    <sdk>
                        <platform>4</platform>
                        <path>${android.sdk.path}</path>
                    </sdk>
                    <undeployBeforeDeploy>true</undeployBeforeDeploy>
                </configuration>
                <extensions>true</extensions>
            </plugin>

            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
   </project>

I'm using Eclipse Juno, ADT 20.0.3, m2e 1.1.0.

Answer 1

I tried the above solutions and still got the error. Only after some more try and error I found out that the hamcrest classes are also contained in another jar: mockito (I was not yet aware that mockito won't work with my instrumentation tests)

So I solved my problem by removing mockito-all.jar from my dependencies and excluded hamcrest from the transitive dependencies of junit like this:

 <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <scope>test</scope>
    <version>4.10</version>
    <exclusions>
        <exclusion>
            <artifactId>hamcrest-core</artifactId>
            <groupId>org.hamcrest</groupId>
        </exclusion>
    </exclusions>
  </dependency>

This exclusion may also be needed for commons-logging (as of the date of writing) because otherwise the apk builder will protest about old classes.

Answer 2

I found the solution. It depends on the JUnit version, because JUnit 4.10 adds JUnit library and hamcrest jar library, although JUnit 4.10 already contains all the hamcrest classes, so hamcrest exists twice then. If I switch back to JUnit 4.8.1, it doesn't add hamcrest as library and the error is gone.

This solution is actually a workaround. Usually the Eclipse Maven plugin should handle this, but Hamcrest/JUnit is a special problem, because JUnit includes Hamcrest, not as dependency, but in code.