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关闭服务后无法获得断路器内容

来源：5-5 整合两个服务

愤怒的二哈

2021-03-30 21:35:24

在我关闭CourseListApplication服务后，通过url访问CoursePrice的/coursesAndPrice无法获得断路器的默认数据，反而报错了。但是访问/coursesInPrices仍然可以获得断路器的内容。

控制台错误：

java.lang.NullPointerException: null
	at com.imooc.course.service.impl.CoursePriceServiceImpl.getCoursesAndPrice(CoursePriceServiceImpl.java:39) ~[classes/:na]
	at com.imooc.course.controller.CoursePriceController.getCoursesAndPrice(CoursePriceController.java:35) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.11.RELEASE.jar:5.1.11.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) ~[tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:836) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1747) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_181]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_181]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.19.jar:9.0.19]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]

service代码：

@Override
public List<CourseAndPrice> getCoursesAndPrice() {
    List<CourseAndPrice> courseAndPriceList = new ArrayList<>();
    List<Course> courseList = courseListClient.courseList();
    for (int i = 0; i < courseList.size(); i++) {
        Course course = courseList.get(i);
        if (course != null){
            CoursePrice coursePrice = getCoursePrice(course.getCourseId());

            CourseAndPrice courseAndPrice = new CourseAndPrice();

            courseAndPrice.setPrice(coursePrice.getPrice());
            courseAndPrice.setCourseId(course.getCourseId());
            courseAndPrice.setId(course.getId());
            courseAndPrice.setName(course.getCourseName());

            courseAndPriceList.add(courseAndPrice);
        }
    }
    return courseAndPriceList;
}

控制层代码：

@GetMapping("/coursesInPrice")
public List<Course> getCourseListInPrice(Integer courseId){
    List<Course> courses = courseListClient.courseList();
    return courses;
}

@GetMapping("/coursesAndPrice")
public List<CourseAndPrice> getCoursesAndPrice(){
    List<CourseAndPrice> coursesAndPrice = coursePriceService.getCoursesAndPrice();
    return coursesAndPrice;
}

求解答

写回答

1回答

好帮手慕小班

2021-03-31

已采纳

同学你好，NullPointerException 空指针异常，由null调用方法或数据，就会报出空指针异常。

这里出现空指针异常是因为在CourseListClientHystrix类中，返回了默认的课程数据，这是课程数据：

http://img.mukewang.com/climg/60640e7b09717eaa07960520.jpg

所以在coursesInPrice中，可以返回断路器中的默认数据，而coursesAndPrice中，在断路器类中并没有对应的数据，所以会出现查询到该数据为null的情况，对应null来调用就会出现了空指针异常了

http://img.mukewang.com/climg/60640f5c09c8dbb617830350.jpg​

祝学习愉快！





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