OSGi Bundle not starting with Felix Host application

Question

I am using Apache Felix in a host application to provide the ability to load extensions at runtime. The mechanism works great but I have some very temperamental behaviour regarding the bundles starting if I include certain dependencies. If for example I use the following in my pom.xml:

<packaging>bundle</packaging>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.felix</groupId>
            <artifactId>maven-bundle-plugin</artifactId>
            <version>2.5.0</version>
            <extensions>true</extensions>
            <configuration>
                <instructions>
                    <Bundle-SymbolicName>${project.groupId}.${project.artifactId}</Bundle-SymbolicName>
                    <Bundle-Name>${project.artifactId}</Bundle-Name>
                    <Bundle-Version>1.0.0</Bundle-Version>
                    <Bundle-Activator>${pom.groupId}.activator.Activator</Bundle-Activator>
                    <Include-Resource>{maven-resources}, {maven-dependencies}</Include-Resource>
                    <Import-Package>*</Import-Package>
                    <Embed-Dependency>jackson-core</Embed-Dependency>
                    <Embed-Transitive>true</Embed-Transitive>
                </instructions>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
            </configuration>
        </plugin>
    </plugins>
</build>
<dependencies>
    <dependency>
        <groupId>org.apache.felix</groupId>
        <artifactId>org.osgi.core</artifactId>
        <version>1.4.0</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjtools</artifactId>
        <version>1.8.2</version>
    </dependency>
    <dependency>
        <groupId>co.ff36</groupId>
        <artifactId>halo.core</artifactId>
        <version>1.0.0</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

Everything works perfectly and the bundle registers and starts. However if I include async-http-client in the bundle it registers but does not start! I have tried embedding the dependency in the bundle even though the parent exposes it by the parent host application. If I look inside the compiled bundle the jar has been included but it still wont actually start.

I tried adding:

    <dependency>
        <groupId>com.ning</groupId>
        <artifactId>async-http-client</artifactId>
        <version>1.9.31</version>
    </dependency>

and modified:

<Embed-Dependency>jackson-core, async-http-client</Embed-Dependency>

Neither of these options work. I am not getting any error in the host application and I just can't work out why some libraries cause this but not others.

Answer 1

After further investigation it turns out that the problem is related to versioning. The bundle MANIFEST.MF that is created explicitly states the versions for some import packages:

Import-Package: ...,com.fasterxml.jackson.core.type;version="[2.4,3)",com.ning.http.client;version="[1.9,2)",
 org.osgi.framework;version="[1.5,2)"

However, the host application does not specify a version:

Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA -> ... com.ning.http.client ...

It appears that the version must be explicitly stated in the host and it must match the bundles import otherwise the bundle won't activate.