How to best import beans to use inside Camel inside Karaf?

Question

I'm using Apache Karaf to run Apache Camel with some other bundles. I need to use a few beans in my Apache Camel blueprint XMLs. I need advice on how to best import beans into Apache Karaf.

My current approach is creating a plain Java project, writing my beans and just compiling to a jar. Then I just drop the jar in my Karaf's deploy folder. This works and I can access my beans inside of my blueprint XMLs.

I'm running into problems with dependencies, though. I have no idea on how to properly manage those. My current approach works, because the libaries I use are already inside of Karaf. Now, I need to use Eclipse Milo for a small OPC UA bean and I don't know how to best include the needed additional dependencies.

The approach I try to use for that is using the maven-assembly-plugin with "jar-with-dependencies". This bundles all dependenices in my jar. This works in a small test scenario, but not for the Eclipse Milo libraries. The jar excees 40mb in size, which is insane to me. It's all just code, how can it get so big?

Anyways, when I try to drop that into Karaf's deploy folder, Karaf runs into an OutOfMemory error and stops working.

If it's any use, heres my POM.

<?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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>test</groupId>
    <artifactId>test</artifactId>
    <version>1</version>

    <name>camelopcua</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>

        <!-- CAMEL -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-core</artifactId>
            <version>3.0.0-M1</version>
            <scope>provided</scope>
        </dependency>
        <!-- some others -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-test-blueprint</artifactId>
            <version>3.0.0-M1</version>
            <scope>provided</scope>
        </dependency>

        <!-- MILO -->
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>sdk-core</artifactId>
            <version>0.2.4</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>sdk-client</artifactId>
            <version>0.2.4</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>sdk-server</artifactId>
            <version>0.2.4</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>stack-core</artifactId>
            <version>0.2.4</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>stack-client</artifactId>
            <version>0.2.4</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.milo</groupId>
            <artifactId>stack-server</artifactId>
            <version>0.2.4</version>
        </dependency>

        <!-- OTHER -->
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongo-java-driver</artifactId>
            <version>3.10.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20160810</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-server</artifactId>
            <version>9.4.15.v20190215</version>
        </dependency>
        <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-camel</artifactId>
            <version>5.6.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.osgi</groupId>
            <artifactId>org.osgi.core</artifactId>
            <version>6.0.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.8</version>
        </dependency>
        <dependency>
            <groupId>org.ow2.asm</groupId>
            <artifactId>asm-commons</artifactId>
            <version>5.0.3</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.4</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.12</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.12</version>
        </dependency>
    </dependencies>

    <build>
        <pluginManagement>          <!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
                <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                <plugin>
                    <artifactId>maven-site-plugin</artifactId>
                    <version>3.7.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-project-info-reports-plugin</artifactId>
                    <version>3.0.0</version>
                </plugin>
            </plugins>
        </pluginManagement>
        <plugins>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

This doesn't seem like a good approach to me. How would I best import some beans so I can use it inside Camel inside Karaf?

Answer 1

I don't know if you just setup karaf and camel on top of JBoss, maybe you can give more details about it.

However, I recommend you to use something like fuse or apache servicemix which give you more capabilities since is also using OSGI, Karaf, Camel, CXF etc.

You can package everything in osgi bundles and manage then in karaf as a features:

So you can create a java project with all your beans and then deploy it as a osgi feature bundle in karaf, Then you can specify dependencies like this wherever you need it:

<?xml version="1.0" encoding="UTF-8"?>
<features
   name="expressco-oms-egifter-service-features-${project.version}"
   xmlns="http://karaf.apache.org/xmlns/features/v1.0.0"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://karaf.apache.org/xmlns/features/v1.0.0 http://karaf.apache.org/xmlns/features/v1.0.0"
>

   <feature
      name="service"
      version="${project.version}"
   >

      <feature version="${java-project.version}">java-project</feature>

   </feature>

</features>

Suppose now you want to instantiate beans from any camel blueprint you have anywhere else:

    <bean id="myBean"
        class="com.javaproject.MyBean">
    </bean>

A more elegant way is to use EJB's, because you can instantiate them even calling them from another JVM running in a different machine in the network.