NullPointerException in proxied job [BATCH-2860]

Igor Shcherbak opened BATCH-2860 and commented

Input data:

• Job configuration is made of "batch:job" xml element with listeners and steps, that resulted in FlowJob created by Spring behind the scenes.
• Around aspect exists with pointcut: 

@Around(value = "execution(* org.springframework.batch.core.Job.execute(..)) && args(jobExecution)")

Goal of aspect is just  to track job execution. 

• Job lunched using custom job launcher with injected org.springframework.batch.core.launch.support.SimpleJobLauncher and org.springframework.batch.core.Job in it 

 

Actual result - NullPointerException in AbstractJob:

java.lang.NullPointerException: nulljava.lang.NullPointerException: null at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:309) [spring-batch-core-4.2.0.RELEASE.jar:4.2.0.RELEASE] at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:147) [spring-batch-core-4.2.0.RELEASE.jar:4.2.0.RELEASE] at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50) [spring-core-5.2.0.RELEASE.jar:5.2.0.RELEASE] at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:140) [spring-batch-core-4.2.0.RELEASE.jar:4.2.0.RELEASE]

Notes:

Job injected to custom launcher proxied:  !image-2019-11-25-14-09-45-183.png!

As a result all fields are null(listener, jobRepository etc), when job is launched - proxy invoke underlying AbstractJob, but because of AbstractJob access those fields directly but not using getters - null pointer occurs. Without aspect, job bean injected to launcher so no issues when job invoked.

 

Possible fix - access fields(like jobRepository and other) in AbstractJob using getters, so proxy call real getters and return non null value

 

Workaround: during custom launcher initialization prepare proxied job injected to it:

public void afterPropertiesSet() throws Exception {
    if (AopUtils.isCglibProxy(job)) {
        // Copy required fields
        setTargetObjectFieldToProxy("jobRepository");
        setTargetObjectFieldToProxy("jobParametersValidator");
        setTargetObjectFieldToProxy("listener");
    }
}

private void setTargetObjectFieldToProxy(String fieldName) throws Exception {
    // Get and initialize field
    Field field = ReflectionUtils.findField(FlowJob.class, fieldName);
    ReflectionUtils.makeAccessible(field);

    // Get wrapped job bean
    Object target = ((Advised) job).getTargetSource().getTarget();

    // Get wrapped job bean field value
    Object fieldValue = ReflectionUtils.getField(field, target);

    // Set value to job wrapper
    ReflectionUtils.setField(field, job, fieldValue);
}

 

 

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Affects: 4.2.0

Attachments:

• image-2019-11-25-14-09-45-183.png (45.52 kB)

Start at AbstractJob.execute, especially AbstractJob.java:309, and trace how a proxied FlowJob is invoked through SimpleJobLauncher. Reproduce the XML batch:job with listeners and steps plus the around aspect described in the issue; done means launching the proxied job no longer raises the reported NullPointerException.