无法让 Feign Client 为基本示例工作

Question

无法让 Feign Client 工作。首先尝试使用 POST。不断遇到与编码器/解码器相关的错误，说类型不正确。 然后在github上找到了一个调用简单GET API的例子，决定试一试。 还是失败了

在 Github 和网上，我看到了多个版本的 Feign Client Spring-Cloud、OpenFeign、Netflix.feign 有不同的版本。 谁能描述一下应该在生产中使用的最好且稳定的 Feign 客户端是什么？

package com.paa.controllers;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient (name="test-service",url="https://www.reddit.com/r")
public interface GetFeignClient {

     @RequestMapping(method = RequestMethod.GET, value = "/java.json")
     public String posts();
}

Controller:

@RestController
@RequestMapping("/some/api")
public class TestWLCController {

  @Autowired
  private GetFeignClient getFeignClient;

  .. some stuff


    @RequestMapping(value="/postSomething",method = RequestMethod.POST)
    @ApiOperation(value = "Configures something",
            notes = "basic rest controller for testing feign")

    public ResponseEntity<SomeResponse> feignPost(
            UriComponentsBuilder builder,
            @ApiParam(name = "myRequest", 
            value = "request for configuring something", 
            required = true)
            @Valid @RequestBody SomeRequest someRequest) {

        String resp = null;
        try {
            resp = getFeignClient.posts();
        } catch (Exception er) {
            er.printStackTrace();
        }

    }
}

应用：

尝试了所有可能的注释排列，认为它可以解决 AutoWire 问题，但仍然失败

@Configuration
@ComponentScan
@EnableAutoConfiguration
//@EnableEurekaClient
@EnableFeignClients

//@SpringBootApplication
//@EnableFeignClients
//@EnableFeignClients(basePackages = {"com.paa.xenia.controllers", "com.paa.xenia.services"})
public class ServiceApplication extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {

        return application.sources(XeniaServiceApplication.class);
    }

    public static void main(String[] args) {

        SpringApplication.run(ServiceApplication.class, args);
    }
}

2016-07-20 18:15:42.406[0;39m [31mERROR[0;39m [35m32749[0;39m [2m---[0;39m [2m[主][0;39m [36mo.s.boot.SpringApplication [0;39m [2m:[0;39m 应用启动失败

org.springframework.beans.factory.BeanCreationException: 错误 创建名为“testWLCController”的bean：注入自动装配 依赖失败；嵌套异常是 org.springframework.beans.factory.BeanCreationException：不能 自动装配字段：私有 com.paa.controllers.GetFeignClient com.paa.controllers.TestWLCController.gfClient；嵌套异常是 org.springframework.beans.factory.BeanCreationException：错误 创建名为 'com.aa..controllers.GetFeignClient' 的 bean： FactoryBean 在创建对象时抛出异常；嵌套异常是 java.lang.NullPointerException 在 org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118) ~[spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 org.springframework.boot.SpringApplication.refresh(SpringApplication.java:766) [spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 org.springframework.boot.SpringApplication.createAndRefreshContext(SpringApplication.java:361) [spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:307) [spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:1191) [spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:1180) [spring-boot-1.3.5.RELEASE.jar:1.3.5.RELEASE] 在 com.paa.ServiceApplication.main(ServiceApplication.java:44) [bin/:na] 引起：org.springframework.beans.factory.BeanCreationException： 无法自动装配字段：私有 com.paa.controllers.GetFeignClient com.paa.controllers.TestWLCController.gfClient；嵌套异常是 org.springframework.beans.factory.BeanCreationException：错误 创建名为 'com.paa.controllers.GetFeignClient' 的 bean： FactoryBean 在创建对象时抛出异常；嵌套异常是 java.lang.NullPointerException 在 org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] 在 org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE] ... 17 com.n 帧 省略

Answer 1

我不确定您是否最终自己弄清楚了，但为了其他可能偶然发现此线程的人，下面是您尝试做的工作示例。我将首先指出一些不正确的地方，或者至少是你的代码中不需要的地方，然后展示我的有效代码。

1. 您应该尽量不要使用url 属性。相反，在bootstrap.yml（或bootstrap.properties）中使用<feign client name>.ribbon.listOfServers 设置服务器列表。这允许客户端负载平衡，因为listOfServers 可以是逗号分隔的列表。
2. 使用 Ribbon 进行 HTTPS 连接，您需要指定 HTTP 连接不需要的两件事。该端口是listOfServers 和<feign client name>.ribbon.IsSecure: true 的一部分。如果没有端口，则连接到端口 80，如果没有 IsSecure，则使用 HTTP。

3. 使用curl 进行测试，我发现Reddit 需要非常 很长时间才能响应。有关如何分解请求-响应周期所用总时间的详细信息，请参阅此 SO post。

   $ curl -v -H "User-Agent: Mozilla/5.0" -w "@curl-format.txt" -o /dev/null -s "https://www.reddit.com/r/java/top.json?count=1"
   { [2759 bytes data]
   * Connection #0 to host www.reddit.com left intact
   time_namelookup:     0.527
   time_connect:        0.577
   time_appconnect:     0.758
   time_pretransfer:    0.758
   time_redirect:       0.000
   time_starttransfer: 11.189
                     ----------
   time_total:         11.218
   

根据 Netflix Wiki，默认读取和连接超时为 3000 毫秒，因此除非您更改这些超时，否则您将始终超时。

4. 您可能已经注意到我在curl 请求中指定了User-Agent 标头。那是因为 Reddis 似乎对此非常挑剔，如果没有指定，大多数时候会返回 HTTP 429“请求过多”。它们不会在响应中返回 Retry-After 标头，因此不知道您需要等待多长时间才能发出另一个请求。
5. Spring Cloud Netflix 和 Netflix Feign 是开源的，因此一些（很多）耐心和调试技巧非常方便。

“说话很便宜。给我看代码。” （托瓦兹，莱纳斯（2000-08-25））。

我使用出色的 Spring Initializr 网站生成了一个 Gradle 应用程序。这是来自build.gradle 文件的 sn-p。

dependencies {
    compile('org.springframework.cloud:spring-cloud-starter-feign')
    compile('org.springframework.boot:spring-boot-starter-web')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

dependencyManagement {
    imports {
        mavenBom "org.springframework.cloud:spring-cloud-dependencies:Camden.SR3"
    }
}

伪装客户端：

@FeignClient(name = "reddit")
public interface RedditClient {
    @RequestMapping(method = GET, value = "/r/java/top.json?count=1",
            headers = {USER_AGENT + "=Mozilla/5.0", ACCEPT + "=" + APPLICATION_JSON_VALUE})
    public String posts();
}

启动应用程序：

@SpringBootApplication
@EnableFeignClients
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @RestController
    static class DemoController {
        @Autowired
        private RedditClient redditClient;

        @GetMapping("/posts")
        public String posts() {
            return redditClient.posts();
        }
    }
}

bootstrap.yml：

reddit:
  ribbon:
    listOfServers: www.reddit.com:443
    ConnectTimeout: 20000
    ReadTimeout: 20000
    IsSecure: true
hystrix.command.default.execution:
  timeout.enabled: true
  isolation.thread.timeoutInMilliseconds: 50000

集成测试：

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class DemoApplicationTest {
    @Autowired
    private TestRestTemplate restTemplate;

    @Test
    public void testGetPosts() {
        ResponseEntity<String> responseEntity = restTemplate.getForEntity("/posts", String.class);

        HttpStatus statusCode = responseEntity.getStatusCode();
        assertThat(String.format("Actual status code: %d, reason: %s.",
                statusCode.value(), statusCode.getReasonPhrase()),
                statusCode.is2xxSuccessful(), equalTo(true));
    }
}

Answer 2

有人有兴趣了解我们是如何做到的，所以为了他们的利益发布答案。

父模块

package com.hitech.module.base;

@EnableFeignClients
public abstract class BaseApplication extends SpringBootServletInitializer {
...
..
}

build.gradle:

buildscript {
    ext {
        springBootVersion = '1.3.5.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
        classpath("io.spring.gradle:dependency-management-plugin:0.5.6.RELEASE")
    }
}
...
...

dependencies {
    compile('io.springfox:springfox-swagger-ui:2.5.0')
    compile('io.springfox:springfox-swagger2:2.5.0')
    compile('org.springframework.cloud:spring-cloud-starter-feign')

子模块

package com.hitech.module.app;

import com.hitech.module.base.BaseApplication;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration;
import org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

@SpringBootApplication(exclude = {MongoDataAutoConfiguration.class, MongoAutoConfiguration.class},
        scanBasePackages = {"com.hitech.module.base", "com.hitech.module.app", })
@EnableFeignClients("com.hitech.module.app.clients")
public class MyServiceApplication extends BaseApplication {

    private static final Logger LOG = LoggerFactory.getLogger(MyServiceApplication.class);

    public static void main(String[] args) {

        String s1 = "google";

        LOG.info ("=== Started Orchestration Service ===");
        SpringApplication.run(MyServiceApplication.class, args);


    }
}

bootstrap.yml

feign:
  hystrix:
    enabled: false
datasource:
  audit:
    mongodb:
      host: localhost
      port: 27019
      database: audit

Answer 3

依赖关系：

<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>

         <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-parent</artifactId>
                <version>Greenwich.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

应用：

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.test.cloud.bookservice.models.Book;

@SpringBootApplication
@RestController
@RequestMapping("/books")
@EnableFeignClients
public class BookServiceApplication {

    Logger logger = LogManager.getLogger(BookServiceApplication.class);

    @Autowired
    private StoreClient storeClient;


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


    @GetMapping("/book")
    public Book findBook() {
            return this.restTemplate.getForObject("http://stores/book", Book.class);
    }

    @FeignClient(name = "StoreClient", url = "127.0.0.1:8089")
    interface StoreClient {
        @RequestMapping(method = RequestMethod.GET, value = "/stores/book", consumes = "application/json")
        Book getBook();
    }

}