[FIXED] Null Pointer Exception when Calling repository in a class implementing Runnable

Issue

I have a project in which there is a use case where a user books a meeting lets suppose for 10am to 11 am with another user. Now on the backend i want to check at 11 am if the meeting went well or not.

For this i am using Scheduled Future and Runnable. Whenever i book a meeting i create a scheduled future with the relevant meeting end time cron expression..which works fine but the problem is that i am not able to access repository or any of the services inside my run function which is necessary. i am getting a Null Pointer Exception

Here is one of the meetingService Code which triggers using endpoint

public String createMeetingSchedulerJobs(){
        BookingDetails booking = repBooking.findAll().get(0);

        //create completion check job
        String[] dateParts = booking.getDateOfMeeting().split("/");
        TaskDefinition taskDefinition = new TaskDefinition();
        taskDefinition.setData(booking.getMeetingId());
        taskDefinition.setActionType(TaskDefinitonType.MEETING_COMPLETION);
        taskDefinition.setCronExpression(miscUtils.generateCronExpression(parseInt(dateParts[0]),parseInt(dateParts[1]),booking.getEndTimeHour(),booking.getEndTimeMinute(),0));
        taskDefinitionBean.setTaskDefinition(taskDefinition);
        taskDefinitionBean.setMiscUtils(miscUtils);
        return taskSchedulerService.scheduleATask(taskDefinition);
    }

the relevant schedulerService code

 public String scheduleATask(TaskDefinition taskDefinition){
        String jobId = UUID.randomUUID().toString();
        taskDefinition.setId(jobId);
        TaskDefinitionBean taskDefinitionBean = new TaskDefinitionBean();
        taskDefinitionBean.setTaskDefinition(taskDefinition);
        Runnable tasklet = taskDefinitionBean;
        ScheduledFuture<?> scheduledTask = taskScheduler.schedule(tasklet, new CronTrigger(taskDefinition.getCronExpression(), TimeZone.getTimeZone(TimeZone.getDefault().getID())));
   
        jobsMap.put(jobId, scheduledTask);
        return jobsMap.toString();
    }

Example Service

@Service
public class MiscellaneousUtils {
    public String returnHello(){
        return "Hello there ~";
    }
}

TaskDefinitionBean.class

@Configurable
@Service
public class TaskDefinitionBean implements Runnable{
    private TaskDefinition taskDefinition;

    private MiscellaneousUtils miscUtils;

    private BeanFactory beanFactory;

    @Override
    public void run() {
        miscUtils = beanFactory.getBean(MiscellaneousUtils.class);
    }

    public TaskDefinition getTaskDefinition(){
        return taskDefinition;
    }
    public void setTaskDefinition(TaskDefinition taskDefinition){
        this.taskDefinition=taskDefinition;
    }
    public void setMiscUtils(MiscellaneousUtils miscUtils){this.miscUtils=miscUtils;}
}

I have tried different types of dependency injection in TaskDefinitionBean.class but not successful. I know there are many relevant and insightful questions which were similar but still couldn't use the approach.

The Error which i am getting is :

java.lang.NullPointerException: null
    at fG.Service.TaskDefinitionBean.run(TaskDefinitionBean.java:38) ~[classes/:na]
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:93) [spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:514) [na:na]
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) [na:na]
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:299) [na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) [na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) [na:na]
    at java.base/java.lang.Thread.run(Thread.java:844) [na:na]

Solution

for dependency injection to work Your bean has to be created by spring, You create it manually

TaskDefinitionBean taskDefinitionBean = new TaskDefinitionBean();

so beanFactory is null

You can Autowire beanFactory in Service and pass it to TaskDefinitionBean

Answered By - lukwas
Answer Checked By - Katrina (JavaFixing Volunteer)