在AbstractWebSocketHandler中注入依赖项

Question

如何在Web Socket处理程序中注入依赖项：

public class WebsocketHandler extends AbstractWebSocketHandler {
    @Autowired
    GreetingMap greetingMap;

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws IOException {
        // NullPointerException here
        String greeting = greetingMap.getSampleGreetings().get("hello") + " " + message.getPayload();
        session.sendMessage(new TextMessage(greeting));
    }
}

上面的代码抛出NullPointerException

这里可能缺少什么？

Answer 1

尝试通过构造函数而不是@Autowired使用依赖项注入：

private GreetingMap greetingMap;

public WebsocketHandler(GreetingMap greetingMap){
    this.greetingMap = greetingMap
}