如果对https://github.com/OpenFeign/feign  不了解的，可以去官网浏览一下。由于spring对其扩展，我们可以利用spring的注解及spring boot 的特性来使用该组件，可参考文档：http://cloud.spring.io/spring-cloud-static/Dalston.SR1/#spring-cloud-feign 。

    下面的例子是spring boot项目中，访问Oauth2资源服务器的资源接口（非集群环境下）。

    maven pom文件需要引入对spring cloud相关依赖：

 <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

 为了使用feign组件，我们增加依赖：

<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
            <exclusions>
                <!--配置中心去掉，会自动连接 -->
                <exclusion>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-config-client</artifactId>
                </exclusion>
            </exclusions>

        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
        <dependency>
            <groupId>com.netflix.feign</groupId>
            <artifactId>feign-okhttp</artifactId>
            <version>8.18.0</version>
        </dependency>

     为了使用spring boot 的自动配置，我们需要引入       @EnableFeignClients 注解，自动扫描 Feign相关代码。

@SpringBootApplication(
        exclude = {DataSourceAutoConfiguration.class,
                MybatisAutoConfiguration.class,
                JpaRepositoriesAutoConfiguration.class,
                HibernateJpaAutoConfiguration.class},
        scanBasePackages = {"com.sdcuike.practice",
                "com.sdcuike.spring.controller.advice"})
@EnableFeignClients
@Slf4j
public class Application {
    public static void main(String[] args) throws UnknownHostException {
        SpringBootApplicationUtil.runSpringBootApplication(log, args, Application.class);
    }
    
}

 为了访问资源服务器上的资源，我们定义demo接口：

/**
 * Created by beaver on 2017/5/27.<br>
 * <p>
 * {@link https://jmnarloch.wordpress.com/2015/10/14/spring-cloud-feign-oauth2-authentication  }
 */
@FeignClient(name = "exampleService",
        url = "${exampleService.ribbon.listOfServers}",
        configuration = {OAuth2FeignAutoConfiguration.class})
@RequestMapping(value = "/springBoot/example"
        , consumes = MediaType.APPLICATION_JSON_UTF8_VALUE
        , produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public interface ExampleServiceFeignClient {
    @GetMapping("/")
    ModelResult<String> home();
}

  由于spring-cloud-feign对feign做了扩展，所以，我们可以使用spring的web相关注解，来使用feign，大大方便了我们的spring 应用。其关键的配置在于：

@FeignClient(name = "exampleService",
        url = "${exampleService.ribbon.listOfServers}",
        configuration = {OAuth2FeignAutoConfiguration.class})

  注解中name属性最新版本必须要求有，而url的出现，主要显示的配置 feign访问的服务地址。

  OAuth2FeignAutoConfiguration类主要是feign组件利用Oauth2的认证token来访问资源服务器上的资源。

/**
 * Created by beaver on 2017/6/3.
 */
@Configuration
public class OAuth2FeignAutoConfiguration {
    
    @Bean
    public RequestInterceptor oauth2FeignRequestInterceptor(@Qualifier("practiceOAuth2RestTemplate") OAuth2RestTemplate oAuth2RestTemplate) {
        return new OAuth2FeignRequestInterceptor(oAuth2RestTemplate);
    }
}

/**
 * Created by beaver on 2017/6/3.
 */
public class OAuth2FeignRequestInterceptor implements RequestInterceptor {
    
    private final Logger LOGGER = LoggerFactory.getLogger(getClass());
    
    private static final String AUTHORIZATION_HEADER = "Authorization";
    
    private static final String BEARER_TOKEN_TYPE = "Bearer";
    
    private final OAuth2RestTemplate oAuth2RestTemplate;
    
    
    public OAuth2FeignRequestInterceptor(OAuth2RestTemplate oAuth2RestTemplate) {
        Assert.notNull(oAuth2RestTemplate, "Context can not be null");
        this.oAuth2RestTemplate = oAuth2RestTemplate;
    }
    
    @Override
    public void apply(RequestTemplate template) {
        LOGGER.debug("Constructing Header {} for Token {}", AUTHORIZATION_HEADER, BEARER_TOKEN_TYPE);
        template.header(AUTHORIZATION_HEADER,
                String.format("%s %s",
                        BEARER_TOKEN_TYPE,
                        oAuth2RestTemplate.getAccessToken().toString()));
        
    }
}

  其主要思路是利用 feign的的扩展RequestInterceptor，对于每次请求我们自动设置Oauth2的AccessToken 头信息。

  对于Oauth2ClientConfig 的配置在此不再复述，具体请看代码：

https://github.com/sdcuike/spring-boot-oauth2-demo/tree/blog-2017-07-16/spring-boot-oauth-resource-server/src/main/java/com/sdcuike/practice