Unable to extend a class from the existing beans


#1

I am trying to extend TaskService and create a customTaskService Bean. I am passing the autowired ProcessConfigurationImpl to the TaskService but i am getting a null pointer exception for CommandExecutor. What is the right way to do this? and why is it failing ?


#2

Hi,

It’s difficult to provide help without the actual code that you are using.
Can you share more information?

Best regards,

Tijs


#3

Following is a custom task service that we created.
Code:
@Component
public class PLTaskServiceImpl extends TaskServiceImpl{
@Autowired
public PLTaskServiceImpl(ProcessEngineConfigurationImpl processEngineConfiguration){
super(processEngineConfiguration);
}

public List getAllTasks(){

public List<PLTaskDTO> getTasks(Map<String,Object> filters, AuthUser authUser, Boolean enrich){


    //add tasks from all the groups that the user is part of
    List<String> roleGroups = authzClient.getRoleGroups(authUser);
    List<Task>  tasks = new ArrayList<>();
    TaskQuery taskQuery = createTaskQuery().active();
    boolean isIdentifierPresent = StringUtils.isNotBlank(authUser.getIdentifier());
    boolean isRoleGroupEmpty = CollectionUtils.isEmpty(roleGroups);
    if (!isIdentifierPresent && isRoleGroupEmpty)
        return new ArrayList<>();

    if(isIdentifierPresent)
        taskQuery = taskQuery.taskAssignee(authUser.getIdentifier());

    if (!isRoleGroupEmpty)
        taskQuery = taskQuery.taskCandidateGroupIn(roleGroups);


    // add tasks whichever is asssigned to him.
    tasks.addAll(taskQuery.orderByTaskDueDate().list());
  return tasks;
}

}

CommandExecutor is coming as null
Following is the exception stack trace when i call getAllTasks():
java.lang.NullPointerException: null
** at org.flowable.task.service.impl.TaskQueryImpl.ensureVariablesInitialized(TaskQueryImpl.java:1443) ~[flowable-task-service-6.4.0.jar:6.4.0]**
at org.flowable.task.service.impl.TaskQueryImpl.executeList(TaskQueryImpl.java:1572) ~[flowable-task-service-6.4.0.jar:6.4.0]
at org.flowable.common.engine.impl.AbstractQuery.list(AbstractQuery.java:116) ~[flowable-engine-common-6.4.0.jar:6.4.0]
at org.flowable.task.service.impl.TaskQueryImpl.list(TaskQueryImpl.java:1921) ~[flowable-task-service-6.4.0.jar:6.4.0]
at com.workflow.services.activity_services.impl.PLTaskServiceImpl.getTasks(PLTaskServiceImpl.java:90) ~[classes/:na]
at com.workflow.controllers.TaskController.getTasks(TaskController.java:40) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) ~[spring-webmvc-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at com.workflow.CORSFilter.doFilter(CORSFilter.java:36) ~[classes/:na]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:209) ~[spring-security-web-5.1.0.RELEASE.jar:5.1.0.RELEASE]
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.1.0.RELEASE.jar:5.1.0.RELEASE]
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.10.RELEASE.jar:5.0.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.34.jar:8.5.34]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_171]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_171]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.34.jar:8.5.34]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_171]

pls let me know if u need more details


#4

I am not sure if you are overriding some of the methods of the TaskServiceImpl.

Not overriding methods

If you are not and you just use to to have extra methods I would advise to inject the TaskService into your own service and use it like that.

Overriding methods

If you are extending some of the methods then you would need to create it differently. In your case the CommandExecutor of the service is not initialised. That is happening later on when the ProcessEngineConfiguration is being initialised. You also need to set the TaskService in the ProcessEngineConfiguration (assuming that you want it to be used by the ProcessEngineConfiguration).
If you are using Spring Boot you can do this through the EngineConfigurationConfigurer.

@Bean
public EngineConfigurationConfigurer<SpringProcessEngineConfiguration> customProcessEngineConfiguration() {
    return engineConfiguration -> {
        engineConfiguration.setTaskService(new PLTaskServiceImpl(engineConfiguration));
    }
}

If you do this then you won’t (and shouldn’t) need to expose the the PlTaskServiceImpl it will be exposed via the ProcessEngineServicesAutoConfiguration.


By looking at your code it seems like you are just adding new methods in this case you can go for the first approach it would be much easier,


#5

thanks for the inputs.
I want to override some existing methods and add new methods to the task service.

In that case, is there any better approach other than extending a class using the EngineConfigurationConfigurer approach and creating another class which is injected with TaskService and use it


#6

If you want to override methods from the service then I would suggest that you extend it with your own implementation and provide that to the ProcessEngineConfiguration through the EngineConfigurationConfigurer