Spring Boot, Autowired is null in ServletContextListener.contextInitialized

Question

I get a NullPointerException by Autowiring in contextInitialized, maybe somebody can help me, thanks a lot.

The Main class

@SpringBootApplication
@CompnentScan
public class Application extends SpringBootServletInitializer {
  public static void main(String[] args) throws Exception {
    SpringApplication.run(Application.class, args);
  }

  @Override
  protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
    return application.sources(Application.class);
  }

  @Bean
  public ProfileAdminListener profileAdminListener() {
    return new ProfileAdminListener();
  }
}

ServletContextListener

@WebListener()
public class ProfileAdminListener implements ServletContextListener {

private final Timer timer = new Timer();

public ProfileAdminListener() {
    setProperties();
}

private void setProperties() {
    ....
}

@Override
public void contextDestroyed(ServletContextEvent sce) {
    timer.cancel();
    timer.purge();
}

@Override
public void contextInitialized(ServletContextEvent sce) {
    startProtokollTask();
}

private void startProtokollTask() {
    ProtokollFileWriteTask task = ProtokollFileWriteTask.getInstance();
    timer.schedule(task, 0, 10000);
}
}

Task

@Component
public class ProtokollFileWriteTask extends TimerTask {

private static ProtokollFileWriteTask instance = new ProtokollFileWriteTask();

@Autowired
private ProtokollService protokollService;

private ProtokollFileWriteTask() {
}

public static ProtokollFileWriteTask getInstance() {
    return instance;
}

@Override
public void run() {
    writeFile();
}

private void writeFile() {
    protokollService.writeProtokollFile("c:\temp");  <---- prtokollService is null
}
}

After start the appplication, I want to start the timetask, but I get a NullPointerException becuase the protokollservice is null. I think the service was not init before use it.

By use normal spring mvc xml config, this is no problem. How to config it by Spring boot? Thanks.

Possible duplicate of [Why is my Spring @Autowired field null?](http://stackoverflow.com/questions/19896870/why-is-my-spring-autowired-field-null) — kryger, Mar 31 '16 at 11:30
Through a chain of calls you ultimately use the `instance` field that's created via the `new` keyword which is thus not managed by Spring, so the `@Autowired` annotation is effectively unused. You'll need to instantiate all your components via Spring to make autowiring work. — kryger, Mar 31 '16 at 11:32
Hi Kryger, you are right, this problem is because I **new** a timetask, this is not controlled by spring. Thanks a lot. — J.Z., Mar 31 '16 at 11:46

score 0 · Accepted Answer · answered Mar 31 '16 at 11:49

0

Kryger's anwswer is right, this problem is because I new a timetask, this is not controlled by spring. Thanks a lot.

answered Mar 31 '16 at 11:49

J.Z.

351
2
15

score 0 · Answer 2 · answered Mar 31 '16 at 19:06

You colud create the new bean with a static method, by example:

@Component
public class ProtokollFileWriterTaskCreator {
  @Autowired
  ProtokollFileWriteTask bean;

  public ProtokollFileWriteTask create() {
    return bean;
  }

}

By other side, modify your other bean :

@Component
public class ProtokollFileWriteTask extends TimerTask {
  @Autowired
  private ProtokolService protokollService;

  @Override
  public void run() {
    writeFile();
  }

  private void writeFile() {
    protokollService.writeProtokollFile("c:\\temp");
  }

}

In weblistener class you should use the creator bean:

@WebListener
public class ProfileAdminListener implements ServletContextListener {
  private final Timer timer = new Timer();

  @Autowired
  ProtokollFileWriterTaskCreator timerTaskFactory;

  public ProfileAdminListener() {
    setProperties();
  }

  private void setProperties() {
    //nothing
  }

  @Override
  public void contextDestroyed(ServletContextEvent sce) {
    timer.cancel();
    timer.purge();
  }

  @Override
  public void contextInitialized(ServletContextEvent sce) {
    startProtokollTask();
  }

  private void startProtokollTask() {
    timer.schedule(timerTaskFactory.create(), 0, 10000);
  }

}

The problem was that you were using the operator new to create beans This is incompatible with the notation @Autowire

Sorry for my bad english

Spring Boot, Autowired is null in ServletContextListener.contextInitialized

2 Answers2