在maven-bundle-plugin中使用javax.servlet包

Question

I am trying an example which uses component factory and everything works fine. My project structure is

Bundle1 
   -- interface
Bundle2
   -- implemenation
Bundl3
   -- factory to produce objects 
Bundle4
   -- factoryprovider.

below is my pom.xml

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.test.java.cintconsumer.CIntConsumer</groupId>
    <artifactId>com.test.java.cintconsumer.CIntConsumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <build>
        <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-scr-plugin</artifactId>
                <version>1.14.0</version>
                <executions>
                    <execution>
                        <id>generate-scr-scrdescriptor</id>
                        <goals>
                            <goal>scr</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-bundle-plugin</artifactId>
                <extensions>true</extensions>
                <version>2.3.5</version>
                <configuration>
                    <instructions>
                        <Bundle-SymbolicName>com.test.java.cintconsumer.CIntConsumer</Bundle-SymbolicName>
                        <Import-Package>
                            *,
                            javax.servlet*;version="[2.5,4)"
                        </Import-Package>
                    </instructions>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <!-- Felix SCR annotations -->
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.apache.felix.scr.annotations</artifactId>
            <version>1.9.6</version>
        </dependency>
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.apache.felix.scr</artifactId>
            <version>1.4.0</version>
        </dependency>
        <dependency>
            <groupId>com.java.test.cinterface.CInterface</groupId>
            <artifactId>com.java.test.cinterface.CInterface</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
    <packaging>bundle</packaging>
</project>

If i remove the import statement

 <Import-Package>*,javax.servlet*;version="[2.5,4)"
    </Import-Package>

classcastexception occurs

java.lang.ClassCastException: org.apache.felix.scr.impl.manager.ComponentFactoryImpl cannot be cast to org.osgi.service.component.ComponentFactory

I am writing a simple application and not using servlet class. Just a class with println statements. Can any one please tell me why we are importing servlet package here.? I know there is a link related to this but there is no clear explanation.

factory provider

@Activate
    public void activate(BundleContext context) throws InvalidSyntaxException {
        serRef = context.getAllServiceReferences(null, "(component.factory=com.test.java.cintconsumer.CIntClient)")[0];
        componentFactory = (ComponentFactory) context.getService(serRef);

        ComponentInstance instance = componentFactory.newInstance(null);
        CIntClient client = (CIntClient) instance.getInstance();
        System.out.println("client " + client);
        client.getCInterface().start("New Component started");
        client.getCInterface().stop("New Component stopped");
    }

bundle 3

@Component(factory = "com.test.java.cintconsumer.CIntClient")
public class CIntClient {

    @Reference(bind = "bind", unbind = "unbind")
    private CInterface cinter;


    @Activate
    public void activate() {
    }

    public void bind(CInterface cinter) {
        this.cinter = cinter;
    }

    public void unbind(CInterface cinter) {
        this.cinter = null;
    }

    public CInterface getCInterface() {
        return cinter;
    }

Apart from the above two classes remaining things are interface and implementation. Just contains method with names start and stop , which inturn will print some strings!. Also activate in provider is called two times while deploying in karaf. Any guess on this. I have verified the same(activate called two times) in greater versions Apache karaf-2.3.11 is working fine and called only once. Is this an issue in Apache Karaf 2.3.10. Could anybody please confirm the same

Answer 1

Most probably either your code or some library you use needs the servlet package. Difficult to say without your code. The maven bundle plugin scans the classes and only imports what is needed.