Spring-Batch proxy class cannot be cast to Class?

Question

I have a spring-batch @Job defined. But when running it (inside tomcat), I'm getting a ClassCastException due to com.sun.proxy.$Proxy.

Why could this be the case? What might be wrong in the following excerpt?

@Service
public class JobService {
    @Autowired
    private JobLauncher launcher;

    public void run() {
        Job job = jobRegistry.getJob("jobname");
        launcher.run(job, params); //line 59
    }
}


@Configuration
@EnableBatchProcessing(modular = true)
public class JobConfig {
    @Bean
    @JobScope
    public MultiResourceItemReader<T> reader(@Value("#{jobParameters['filename']}") Resource csv) throws Exception {
        MultiResourceItemReader<T> itemReader = new MultiResourceItemReader<>();
        //...
        return itemReader;
    }

    @Bean
    public JobScope jobScope() {
        return new JobScope();
    }
}

Result:

java.lang.ClassCastException: com.sun.proxy.$Proxy135 cannot be cast to org.springframework.batch.item.file.MultiResourceItemReader
    at org.springframework.batch.item.file.MultiResourceItemReader$$FastClassBySpringCGLIB$$ad846cb.invoke(<generated>) ~[spring-core-4.0.6.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:708) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:133) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:121) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:644) ~[spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.batch.item.file.MultiResourceItemReader$$EnhancerBySpringCGLIB$$3a188c22.close(<generated>) ~[spring-core-4.0.6.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.item.support.CompositeItemStream.close(CompositeItemStream.java:85) ~[spring-batch-infrastructure-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.step.item.ChunkMonitor.close(ChunkMonitor.java:106) ~[spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.item.support.CompositeItemStream.close(CompositeItemStream.java:85) ~[spring-batch-infrastructure-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.step.tasklet.TaskletStep.close(TaskletStep.java:305) ~[spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:267) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:148) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.job.AbstractJob.handleStep(AbstractJob.java:386) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.job.SimpleJob.doExecute(SimpleJob.java:135) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:304) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:135) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50) [spring-core-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:128) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_51]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_51]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_51]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_51]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317) [spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) [spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) [spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration$PassthruAdvice.invoke(SimpleBatchConfiguration.java:127) [spring-batch-core-3.0.1.RELEASE.jar:3.0.1.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207) [spring-aop-4.0.6.RELEASE.jar:4.0.6.RELEASE]
    at com.sun.proxy.$Proxy52.run(Unknown Source) [?:?]
    at my.JobService.run(JobExecutor.java:59)

Answer 1

If you don't need a concrete type for reader return a ItemReader<T> from reader() function. @JobScope proxy the target class with a CGLIB proxy by default.