java - 无法让 @Resource 注解在 Spring Boot 中工作

Question

我一直在开发一个使用 Websockets 的项目，并且我需要在多个类和线程中使用相同的 HashMap。阅读了一些内容后，我发现使用 @Resource 注释是最好的。但我无法让它工作，并且在打印 String 时只得到 null，在使用 ConcurrentHashMap 执行任何操作时得到 NullPointerException。这是部分代码。

SocketHandler.java

@Component
public class SocketHandler extends TextWebSocketHandler {

    @Resource(name = "teststring")
    private String testString;

    private ConcurrentHashMap<WebSocketSession, UserPlayer> sessions;

    @Resource(name="sessions")
    public void setSessions(ConcurrentHashMap<WebSocketSession, UserPlayer> sessions){
        System.out.println("Im in @resource");
        this.sessions=sessions;
    }

    @Override
    public void afterConnectionEstablished(final WebSocketSession session) throws Exception {
        System.out.println(testString);
        sessions.put(session, new UserPlayer());
        System.out.println("Got connection " + session);
    }
}

AplicationContextResource.java

@Configuration
public class ApplicationContextResource{

    @Bean(name="sessions")
    public ConcurrentHashMap<WebSocketSession, UserPlayer> sessions(){
        ConcurrentHashMap<WebSocketSession, UserPlayer> sessions = new  ConcurrentHashMap<WebSocketSession, UserPlayer>();
        System.out.println("bean sessions!!");
        return sessions;
    }

    @Bean(name="teststring")
    public String testString(){
        String str = new String("12345");
        return str;
    }
}

BeanPostProc.java

@Configuration
public class BeanPostProc {

    @Bean
    public CommonAnnotationBeanPostProcessor commonAnnotationBeanPostProcessor(){
        CommonAnnotationBeanPostProcessor cBeanPostProcessor = new CommonAnnotationBeanPostProcessor();
        cBeanPostProcessor.setAlwaysUseJndiLookup(true);
        return cBeanPostProcessor;
    }
}

这是服务器启动和客户端连接后的控制台输出。

020-05-07 22:03:28.417  INFO 3132 --- [           main] com.soluna.slith.DemoApplication         : Starting DemoApplication on Racunalo with PID 3132 (D:\Git\slytherin\server\slith\target\classes started by Sebastijan in d:\Git\slytherin\server\slith)
2020-05-07 22:03:28.421  INFO 3132 --- [           main] com.soluna.slith.DemoApplication         : No active profile set, falling back to default profiles: default
2020-05-07 22:03:29.395  INFO 3132 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'beanPostProc' of type [com.soluna.slith.config.BeanPostProc$$EnhancerBySpringCGLIB$$524027f] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-05-07 22:03:29.758  INFO 3132 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-05-07 22:03:29.771  INFO 3132 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-05-07 22:03:29.772  INFO 3132 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.30]
2020-05-07 22:03:29.874  INFO 3132 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-05-07 22:03:29.875  INFO 3132 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1365 ms
bean sessions!!
Im in @resource
2020-05-07 22:03:30.193  INFO 3132 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-05-07 22:03:30.458  INFO 3132 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-05-07 22:03:30.461  INFO 3132 --- [           main] com.soluna.slith.DemoApplication         : Started DemoApplication in 2.511 seconds (JVM running for 3.154)
2020-05-07 22:04:31.705  INFO 3132 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-05-07 22:04:31.705  INFO 3132 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-05-07 22:04:31.722  INFO 3132 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 17 ms
null
2020-05-07 22:04:31.808 ERROR 3132 --- [nio-8080-exec-1] w.s.h.ExceptionWebSocketHandlerDecorator : Closing session due to exception for StandardWebSocketSession[id=6aedf417-075a-851d-bb92-16e32ef76915, uri=ws://localhost:8080/game]

java.lang.NullPointerException: null
    at com.soluna.slith.controller.SocketHandler.afterConnectionEstablished(SocketHandler.java:65) ~[classes/:na]

我的项目没有 XML，所有示例都显示基于 XML 的 bean 配置。尝试使用和不使用 .setAlwaysUseJndiLookup(true)。我是否搞砸了 CommonAnnotationBeanPostProcessor bean？

Answer 1

经过阅读并尝试了很多事情后，我终于发现了错误。该错误不在上述任何类中，而是在 WebSocket 配置中。甚至不需要带有 CommonAnnotationBeanPostProcessor 的 BeanPostProc.java。

WebSocket 配置之前:

@Configuration 
@EnableWebSocket 
public class WebSocketConfig implements WebSocketConfigurer {

    @Override 
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(new SocketHandler(), "/game").setAllowedOrigins("*");
    }
  }

WebSocket 配置现在:

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

    @Autowired
    private SocketHandler socketHandler;

    @Override 
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(socketHandler, "/game").setAllowedOrigins("*");
    }
}

错误是我正在创建一个新的 SocketHandler 实例，该实例不是由 Spring 管理的，也没有正确 Autowiring 。修复错误后，Bean 注入(inject)正在使用 @Resource 和 @Autowired 注释。