Question

我是多线程的新手。我试图使用Crud存储库在sql数据库中保存对象列表。但是我在保存操作中得到了空指针异常。下面是我的代码和异常。线程类

public class PrescriptionThread implements Runnable{
  private MedicineService medServ = new MedicineService();
  private  Presciption pres ;

  public PrescriptionThread(Presciption pres) {
    this.pres = pres;
  }

  @Override
  public void run() {
    medServ.savePrescription(pres);
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
  }
}

服务等级

@Service
public class MedicineService {

@Autowired
private PrescriptionRepository presRepo;

public void storePrescription(List<Presciption> payload) {

    ExecutorService executorService = Executors.newFixedThreadPool(5);
    for (Presciption presciption : payload) {
        Runnable runnable = new PrescriptionThread(presciption);
        executorService.execute(runnable);
    }
    executorService.shutdown();

    while(!executorService.isTerminated()) {}
}


public synchronized void savePrescription(Presciption pres) {
        presRepo.save(pres);
}
}

存储库

@Repository
public interface PrescriptionRepository extends CrudRepository<Presciption, Integer> {

}

我正在接受治疗 presRepo.save（pres）;

Exception in thread "pool-1-thread-3" Exception in thread "pool-1-thread-1" Exception in thread "pool-1-thread-2" java.lang.NullPointerException
at com.cerner.api.service.MedicineService.savePrescription(MedicineService.java:86)
at com.cerner.api.util.PrescriptionThread.run(PrescriptionThread.java:16)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)

如果我不使用线程而只是说

for (Presciption presciption : payload) {
        presRepo.save(pres);
    }

它工作正常，我能够将其保存到数据库。但是我想实现线程。预先感谢。

Answer 1

作为此处的结果：

private MedicineService medServ = new MedicineService();

实例“ medServ”是春季IOC管理，如果您“新建”它，也许因为它是“ @Autowire”而没有得到“ PrescriptionRepository”的实例，则在您调用{{1 }}。但是如果您不使用Thread，则意味着实例本身不是新的，因此可以正常工作

Answer 2

我如下修改了我的线程类，并且能够获得bean。

result = np.array([[2,2],[3,3],[4,4]])

在Spring中使用多线程时出现NullPointer异常

2 个答案: