generate a custom workitemhandler with the maven archetype: mvn archetype:generate -DarchetypeGroupId=org.jbpm -DarchetypeArtifactId=jbpm-workitems-archetype -DarchetypeVersion=7.42.0.Final -DgroupId=org.jbpm.contrib -DartifactId=custom-workitem -DclassPrefix=Custom -Dversion=7.42.0-SNAPSHOT -DarchetypeCatalog=local note: I needed to add to pom.xml for a successfull build:     <maven.compiler.target>1.8</maven.compiler.target>     <maven.compiler.source>1.8</maven.compiler.source> Add a simple output in the CustomWorkItemHandler#executeWorkItem function:     System.out.println("Hello World"); Now start the docker container: docker run -p 8080:8080 -p 8001:8001 -d --name jbpm-server-full jboss/jbpm-server-full:latest Browse to  http://localhost:8080/business-central  and login with wbadmin account  Navigate to  Admin  ->  Custom Tasks Administration Upload a jar that contains a sample workitemhandler. Then set the entry to "ON". (Screenshot_1.png) Create a sample Project. Open the Project Settings and Install the "CustomDefinitions" entry. (Screenshot_2.png) If you like hit F5 and check that the entry was generated within Deployments -> Work Item Handlers. Create a sample process that uses the Service task. (Screenshot_3.png) Build and Deploy the Project. (Screenshot_4.png) Direct after the success message comes the error message. (Screenshot_5.png) Details are not shown in the deployment info. (Screenshot_6.png) I attached the Stacktrace as attachment too. (Stacktrace.txt)