如何在使用 Spring Boot 和 Eureka Server 时修复错误 java.net.UnknownHostException？

Question

我有一个名为“documents-microservice”的 Spring Boot 微服务，它在 Eureka Server 中注册。 我正在尝试使用 URL 中的名称和RestTemplate访问此微服务，如下所示：

ResponseEntity<String> response =    restTemplate.exchange("http://documents-microservice/document-name", HttpMethod.POST, entity, String.class);

尽管我确定在端口 8761 上运行的 Eureka Server 上可以使用该服务名称（见下图），但我仍然收到以下错误：

错误：

org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://documents-microservice/document-name": documents-microservice; nested exception is java.net.UnknownHostException: documents-microservice
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:674)
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:621)
    at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:539)
    at ae.gov.adm.saeed.web.controller.util.CircularsControllerUtil.circularListView(CircularsControllerUtil.java:196)
    at ae.gov.adm.saeed.web.controller.CircularsController.viewCircularList(CircularsController.java:58)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    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 ae.gov.adm.saeed.web.security.AuthFilter.doFilter(AuthFilter.java:335)
    at ae.gov.adm.saeed.web.security.AuthFilter.doFilter(AuthFilter.java:610)
    at ae.gov.adm.common.web.filter.AbstractFilter.doFilter(AbstractFilter.java:47)
    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:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:417)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.UnknownHostException: documents-microservice
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at java.net.Socket.connect(Socket.java:538)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
    at sun.net.www.http.HttpClient.New(HttpClient.java:339)
    at sun.net.www.http.HttpClient.New(HttpClient.java:357)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1220)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1156)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:984)
    at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:78)
    at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
    at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:660)
    ... 52 more
I/O error on POST request for "http://documents-microservice/document-name": documents-microservice; nested exception is java.net.UnknownHostException: documents-microservice

更新：请注意，我在客户端有以下设置 RestTemplate 的方法：

    @Bean //this methods will be executed only once to avoid getting multiple instances.
    @LoadBalanced //I will not give you service URL, but rather a hint for what you need to discover.
    public RestTemplate getRestTemplate()
    {
         final RestTemplate restTemplate = new RestTemplate();

         System.out.println("rest template defined");

         return  restTemplate;
    }

更新：请注意，目前，我的客户端代码不是 Spring Boot 应用程序。

Answer 1

您需要做几件事：

• 第一：您需要的不是在客户端中的 RestTemplate 配置，而是在调用该客户端的service(1)中

@Configuration
public class WebClientConfiguration {

    @Bean @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }
}

• 第二：需要同服务的pom.xml中对应的依赖(1)

• 第三：在你的主应用程序中添加@EnableDiscoveryClient

和其他配置一样，但是你必须提供一个完整的例子来帮助你更多。
这个例子可以帮助你

Answer 2

您可以通过@Feign 客户端按名称“documents-microservice”访问它，否则您应该尝试网关 EG，hqtpm001....:8081

此外，Eureka 服务器不是应用程序的主机，它或多或少是交通警察，让您作为客户端知道去哪里获取应用程序。 又名服务注册中心