Spring Cloud - 在 Zuul 中使用 @LoadBalaneced RestTemplate

Question

我的项目中有一个通用的 Spring Cloud 架构：用于服务发现的 eureka，作为反向代理的 zuul 和一些微服务。我希望能够以编程方式从 zuul 访问微服务。由于 zuul 由 Ribbon 支持，我只想自动连接 @LoadBalanced RestTemplate，但显然这不起作用。下面是我的小测试设置。

ZuulGatewayApplication.java：

@SpringBootApplication
@EnableZuulProxy
@EnableEurekaClient
public class ZuulGatewayApplication {

    public static void main(String[] args) {
        SpringApplication.run(ZuulGatewayApplication.class, args);
    }

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

SomeService.java：

@RequiredArgsConstructor
@Service
@Slf4j
public class SomeService {
    private final RestTemplate restTemplate;

    @PostConstruct
    public void init() {
        ResponseEntity<Void> response = restTemplate.getForEntity("http://my-service/notify", Void.class);
    }
}

这里是堆栈跟踪的相关部分：

Caused by: org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://my-service/notify": my-service; nested exception is java.net.UnknownHostException: my-service
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:748) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:674) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.client.RestTemplate.getForEntity(RestTemplate.java:342) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at xxx.xxx.xxxx.zuulgateway.service.SomeService.init(SomeService.java:40) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:567) ~[na:na]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:389) ~[spring-beans-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:333) ~[spring-beans-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:157) ~[spring-beans-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    ... 38 common frames omitted
Caused by: java.net.UnknownHostException: my-service
    at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:220) ~[na:na]
    at java.base/java.net.Socket.connect(Socket.java:591) ~[na:na]
    at java.base/java.net.Socket.connect(Socket.java:540) ~[na:na]
    at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:182) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:474) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:569) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:242) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:341) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:362) ~[na:na]
    at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1242) ~[na:na]
    at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1181) ~[na:na]
    at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1075) ~[na:na]
    at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1009) ~[na:na]
    at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:76) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:739) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]

是否需要配置其他内容才能获得正确的RestTemplate？我还尝试使用@RibbonClient 注释 MainClass，但错误消息保持不变。

Answer 1

它在后期构造中不起作用。您需要监听像 ApplicationReadyEvent 这样的事件。

public class SomeService
        implements ApplicationListener<ApplicationReadyEvent> {
    private final RestTemplate restTemplate;

    @Override
    public void onApplicationEvent(ApplicationReadyEvent event) {
        ResponseEntity<Void> response = restTemplate.getForEntity("http://my-service/notify", Void.class);
    }
}