启用 Hystrix 后自动连线不起作用

Question

我遇到了一个问题，当我在微服务中添加Hystrix(EnableHystrix)时，自动连接不起作用。

控制器类:

@RestController
@RequestMapping("/login")
@Slf4j
public class LoginController {
@Autowired
ILoginService loginService;

@ApiOperation(value = "Validate user credentials", response = LoginUser.class)
@PostMapping(value = "/validateCredentials")
private ResponseEntity<LoginUser> validateUserCredentials(@RequestBody LoginUser logginUser) {
LoginUser user=loginService.validateUser(logginUser);
......
.....
}
}

自动装配ILoginService没有Hystrix也能正常工作

但是当我添加依赖时(版本2.2.6发布)

<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

并使Hystrix为:

@EnableFeignClients("com.abcd")
@SpringBootApplication
@EnableHystrix
public class MyApplication{
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
}

ILoginService自动加载失败NullPointerException当尝试访问autowired属性时抛出。

我让这个配置在其他微服务中工作得很好，但是在这个微服务中失败了。这里出了什么问题?

编辑:加亮是:

java.lang.NullPointerException
at com.demo.login.controller.LoginController.validateUserCredentials(LoginController.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)2021-01-28 17:09:12.999 DEBUG 1800 --- [nio-9200-exec-8] com.demo.login.ExceptionsHelper      : Exception: 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)

Answer 1

在当前的形式下，很难说到底发生了什么。因此，我将提供一些可以导致解决方案的想法:

你说

1. ,

当试图访问autowired属性时，ILoginService的自动连接失败并抛出NullPointerException

通常当可以自动装配一个bean时，因为它不存在之类的，spring应该在启动时抛出异常，并且不可能"访问"它。autowired属性在启动过程中，因为系统不会启动，所以这是令人困惑的。也许如果你能提供一个堆栈跟踪和你试图访问属性的地方，它会变得更清楚…

2. 理论上有可能(stacktrace可以证明这一点)有人试图在之前访问属性自动装配实际上执行了。从技术上讲，它在春季通过BeanPostProcessor实现，具有一定的优先级，可能会与其他bean post处理器竞争。

尝试重写控制器以使用构造函数注入(以便spring在控制器构造期间注入ILoginService):

@RestController
public class LoginController {
// Note, no autowiring here
private final ILoginService loginService;
// If you are on old spring you need to mark this constructor with @Autowired,
// in the recent spring versions its not required anymore as long as this is the only 
// constructor of your class
public LoginController(ILoginService loginService) {
this.loginService = loginService;
}

3. 在你这样做之后，试着在构造函数中放置一个断点，看看到底注入了什么(这是在这种情况下构造函数注入的一个优势)