spring-cloud-starter-ribbon 缺少 HTTP 客户端依赖项

Question

我有一个简单的 Spring 引导应用程序，它有一个简单的 REST 客户端，看起来像这样：

@Service
public class MyRestClient {

  private static final String url = "http://localhost:8080/";

  private RestTemplate restTemplate;

  @Autowired
  public MyRestClient(RestTemplate restTemplate) {
    this.restTemplate = restTemplate;
  }

  public String invoke() {
    return restTemplate.getForObject(url, String.class);
  }
}

这与 Spring Boot 完美配合。

现在我正尝试将 Spring Cloud 添加到项目中以实现功能区客户端负载平衡。我点击了这里的链接：

https://spring.io/guides/gs/client-side-load-balancing/

或这里的这个，它似乎是复制和粘贴但具有更多更新的依赖项：

http://www.baeldung.com/spring-cloud-rest-client-with-netflix-ribbon

即使不向 MyRestClient 添加任何注释，我添加以下内容的那一刻：

<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
<version>1.3.4.RELEASE</version>
</dependency>

我得到以下异常：

 Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.client.RestTemplate]: Factory method 'restTemplate' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/http/impl/client/HttpClients
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE]
        ... 31 common frames omitted
    Caused by: java.lang.NoClassDefFoundError: org/apache/http/impl/client/HttpClients
        at org.springframework.http.client.HttpComponentsClientHttpRequestFactory.<init>(HttpComponentsClientHttpRequestFactory.java:88) ~[spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_131]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_131]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_131]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_131]
        at java.lang.Class.newInstance(Class.java:442) ~[na:1.8.0_131]
        at org.springframework.beans.BeanUtils.instantiate(BeanUtils.java:77) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE]
        at org.springframework.boot.web.client.RestTemplateBuilder.detectRequestFactory(RestTemplateBuilder.java:596) ~[spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE]
        at org.springframework.boot.web.client.RestTemplateBuilder.configureRequestFactory(RestTemplateBuilder.java:559) ~[spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE]
        at org.springframework.boot.web.client.RestTemplateBuilder.configure(RestTemplateBuilder.java:527) ~[spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE]
        at org.springframework.boot.web.client.RestTemplateBuilder.build(RestTemplateBuilder.java:515) ~[spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE]
        at org.springframework.boot.web.client.RestTemplateBuilder.build(RestTemplateBuilder.java:501) ~[spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE]

为什么我的 REST 客户端在没有此依赖项的情况下工作，但没有添加任何注释或任何东西，当我添加此依赖项时，我得到此异常？

我尝试从文档或示例中添加各种依赖项，例如 spring-cloud-dependencies（似乎已弃用）、spring-cloud-netflix 等无济于事。

添加什么正确的依赖关系才能让它工作？

Answer 1

看起来 this forum post and the dependency you need for HttpClients is org.apache.httpcomponents/httpclient 中的问题至少是 4.3.3。

Answer 2

您的功能区依赖项通过 ribbon-httpclient 2.2.2

管理以下工件，最高版本为 4.5.3

<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcomponents-client</artifactId>
<version>4.5.3</version>

我建议为 httpcomponents-client 添加显式依赖项并将其从所有其他项中排除。

换句话说尝试在编译时添加它。不是运行时：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

spring-cloud-starter-ribbon 缺少 HTTP 客户端依赖项

Missing HTTP client dependencies for spring-cloud-starter-ribbon

spring

rest

spring-boot

spring-cloud

spring-cloud-netflix