问题描述
我遇到了一个问题，当我在微服务中添加 Hystrix(EnableHystrix) 时，自动装配不起作用。
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);
......
.....
}
}
ILoginService 的自动装配在没有 Hystrix 的情况下完美运行。
但是当我添加依赖项时（2.2.6 版发布）
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
并启用 Hystrix 为：
@EnableFeignClients("com.abcd")
@SpringBootApplication
@EnableHystrix
public class MyApplication{
public static void main(String[] args) {
SpringApplication.run(MyApplication.class,args);
}
}
ILoginService 的自动装配失败，并在尝试访问自动装配属性时抛出 NullPointerException。
我有这个配置在其他微服务中工作正常，但在这个特定的微服务中失败。这里出了什么问题？
编辑： 堆栈跟踪是：
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)
解决方法
在目前的形式中，很难说到底发生了什么。 因此，我将提供一些可能导致解决方案的想法：
- 你说，
尝试访问自动装配属性时，ILoginService 的自动装配失败并抛出 NullPointerException。
通常，当可以自动装配 bean 时，因为它不存在或其他原因，spring 应该在启动期间抛出异常，并且在 statrup 期间不可能“访问”自动装配的属性，因为系统不会启动，所以这很混乱。也许如果您可以提供堆栈跟踪以及您尝试访问该属性的位置，它可能会变得更加清晰......
- 理论上有可能（再次堆栈跟踪可以表明）有人试图在自动装配实际执行之前访问该属性。从技术上讲，它是在 spring 中通过 BeanPostProcessor 实现的，具有一定的优先级，可能会与其他 bean 后处理器竞争。
尝试重写控制器以使用构造函数注入（这样spring会在控制器的构建过程中注入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;
}
- 执行此操作后，尝试在构造函数中放置一个断点并查看究竟注入了什么（在这种情况下，这是构造函数注入的一个优势）