Le service @Autowired à l'intérieur de @Component renvoie une exception de pointeur nul

Question

Mon application Web Spring renvoie java.lang.NullPointerException lorsque j'essaie d'utiliser un service qui est Autowired dans un composant.

J'ai essayé des solutions here mais cela n'a pas fonctionné pour moi puisque j'utilise déjà @component.

Voici ma pleine exception:

java.lang.NullPointerException 
    at ir.yasharne.rpi.websocket.MyStompSessionHandler.handleFrame(MyStompSessionHandler.java:81) 
    at org.springframework.messaging.simp.stomp.DefaultStompSession.invokeHandler(DefaultStompSession.java:448) 
    at org.springframework.messaging.simp.stomp.DefaultStompSession.handleMessage(DefaultStompSession.java:399) 
    at org.springframework.web.socket.messaging.WebSocketStompClient$WebSocketTcpConnectionHandlerAdapter.handleMessage(WebSocketStompClient.java:342) 
    at org.springframework.web.socket.sockjs.client.AbstractClientSockJsSession.handleMessageFrame(AbstractClientSockJsSession.java:271) 
    at org.springframework.web.socket.sockjs.client.AbstractClientSockJsSession.handleFrame(AbstractClientSockJsSession.java:213) 
    at org.springframework.web.socket.sockjs.client.WebSocketTransport$ClientSockJsWebSocketHandler.handleTextMessage(WebSocketTransport.java:162) 
    at org.springframework.web.socket.handler.AbstractWebSocketHandler.handleMessage(AbstractWebSocketHandler.java:43) 
    at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter.handleTextMessage(StandardWebSocketHandlerAdapter.java:110) 
    at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter.access$000(StandardWebSocketHandlerAdapter.java:42) 
    at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter$3.onMessage(StandardWebSocketHandlerAdapter.java:81) 
    at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter$3.onMessage(StandardWebSocketHandlerAdapter.java:78) 
    at org.apache.tomcat.websocket.WsFrameBase.sendMessageText(WsFrameBase.java:395) 
    at org.apache.tomcat.websocket.WsFrameBase.processDataText(WsFrameBase.java:495) 
    at org.apache.tomcat.websocket.WsFrameBase.processData(WsFrameBase.java:294) 
    at org.apache.tomcat.websocket.WsFrameBase.processInputBuffer(WsFrameBase.java:133) 
    at org.apache.tomcat.websocket.WsFrameClient.processSocketRead(WsFrameClient.java:95) 
    at org.apache.tomcat.websocket.WsFrameClient.resumeProcessing(WsFrameClient.java:209) 
    at org.apache.tomcat.websocket.WsFrameClient.access$300(WsFrameClient.java:31) 
    at org.apache.tomcat.websocket.WsFrameClient$WsFrameClientCompletionHandler.doResumeProcessing(WsFrameClient.java:186) 
    at org.apache.tomcat.websocket.WsFrameClient$WsFrameClientCompletionHandler.completed(WsFrameClient.java:163) 
    at org.apache.tomcat.websocket.WsFrameClient$WsFrameClientCompletionHandler.completed(WsFrameClient.java:148) 
    at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) 
    at sun.nio.ch.Invoker$2.run(Invoker.java:218) 
    at sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
    at java.lang.Thread.run(Thread.java:745) 

ligne 81 est moduleService.saveModule(module); dans MyStompSessionHandler.java:

@Component 
public class MyStompSessionHandler extends StompSessionHandlerAdapter { 

    @Autowired 
    private ModuleService moduleService; 

    @Override 
    public void afterConnected(StompSession session, StompHeaders connectedHeaders) { 
     session.subscribe("/topic/messages", this); 
    } 

    @Override 
    public Type getPayloadType(StompHeaders headers) { 
     return ServerMessage.class; 
    } 

    @Override 
    public void handleFrame(StompHeaders headers, Object payload) { 
     ServerMessage message = (ServerMessage) payload; 
     if (message.getTopic().equals("newModule")){ 
      ObjectMapper mapper = new ObjectMapper(); 
      try { 
       Map<String, Object> readValue = mapper.readValue(message.getMessage(), Map.class); 
       int id = (int) readValue.get("id"); 
       boolean programmable = (boolean) readValue.get("programmable"); 
       float value = Float.parseFloat(readValue.get("value").toString()); 
       Module module = new Module(); 
       module.setId(id); 
       module.setProgrammable(programmable); 
       module.setValue(value); 
       moduleService.saveModule(module); 
      } catch (IOException e) { 
       System.out.println("HandlerFrame: "); 
       e.printStackTrace(); 
      } 
     } 
    } 

    @Override 
    public void handleException(StompSession session, StompCommand command, StompHeaders headers, byte[] payload, Throwable exception) { 
     exception.printStackTrace(); 
    } 
} 

et mon WebAppConfiguration.java:

@Configuration 
@EnableWebMvc 
@ComponentScan(basePackages = "ir.yasharne.rpi") 
public class WebAppConfiguration extends WebMvcConfigurerAdapter { 

    @Bean 
    public ViewResolver viewResolver() { 
     InternalResourceViewResolver viewResolver = new InternalResourceViewResolver(); 
     viewResolver.setViewClass(JstlView.class); 
     viewResolver.setPrefix("/WEB-INF/views/"); 
     viewResolver.setSuffix(".jsp"); 
     return viewResolver; 
    } 

    @Override 
    public void addResourceHandlers(ResourceHandlerRegistry registery){ 
     registery.addResourceHandler("/static/**").addResourceLocations("/static/"); 
    } 
} 

ModuleServiceImpl.java:

@Service("moduleService") 
@Transactional 
public class ModuleServiceImpl implements ModuleService { 

    @Autowired 
    private ModuleDao moduleDao; 

    @Override 
    public void saveModule(Module module) { 
     moduleDao.saveModule(module); 
    } 
} 

Comment puis-je résoudre ce problème?

BTW, je peux autowire et utiliser moduleService à l'intérieur du contrôleur et de l'utiliser sans problème

Answer 1

Quel est le paquet pour MyStompSessionHandler? Je suppose que ce n'est pas couvert par ir.yasharne.rpi. Essayez de déplacer sous ce paquet (ir.yasharne.rpi), ou mettre à jour @ComponentScan(basePackages = "ir.yasharne.rpi")-@ComponentScan(basePackages = {"ir.yasharne.rpi", "package.of.MyStompSessionHandler"})

Je devine MyStompSessionHandler est pas sur le chemin « de balayage composante » et c'est pourquoi les dépendances autowired dans ce ne sont pas pris.