SpringCloud 使用Feign访问服务

Feign简介：

　　声明式的Rest  WEB 服务的客户端， https://github.com/OpenFeign/feign。Spring Cloud 提供了Spring-cloud-starter-openfeign的支持

Feign的简单使用

　　pom文件

    <!--引入版本号-->
      <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR1</spring-cloud.version>
    </properties>
    <!--dependency引入-->    

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

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>

<!--eureka的支持-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

<!--dependencyManagement 引入spring cloud 的dependency-->
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>

　　开启Feign的支持

　　　　@EnableFeignClients

@SpringBootApplication
@Slf4j
@EnableFeignClients // 开启Feign支持
public class CustomerServiceApplication {}

注入CloseableHttpClient

　　

@Bean
    public CloseableHttpClient httpClient() {
        return HttpClients.custom()
                .setConnectionTimeToLive(30, TimeUnit.SECONDS)
                .evictIdleConnections(30, TimeUnit.SECONDS)
                .setMaxConnTotal(200)
                .setMaxConnPerRoute(20)
                .disableAutomaticRetries()
                // 存活策略
                .setKeepAliveStrategy(new CustomConnectionKeepAliveStrategy())
                .build();
    }

//CustomConnectionKeepAliveStrategy
public class CustomConnectionKeepAliveStrategy implements ConnectionKeepAliveStrategy {
    private final long DEFAULT_SECONDS = 30;

    @Override
    public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
        return Arrays.asList(response.getHeaders(HTTP.CONN_KEEP_ALIVE))
                .stream()
                .filter(h -> StringUtils.equalsIgnoreCase(h.getName(), "timeout")
                        && StringUtils.isNumeric(h.getValue()))
                .findFirst()
                .map(h -> NumberUtils.toLong(h.getValue(), DEFAULT_SECONDS))
                .orElse(DEFAULT_SECONDS) * 1000;
    }
}

定义Feign接口

@FeignClient(name = "my-service", contextId = "order")
public interface OrderService {
    @GetMapping("/order/{id}")
    Order getOrder(@PathVariable("id") Long id);

    @PostMapping(path = "/order/", consumes = MediaType.APPLICATION_JSON_VALUE,
            produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    Order create(@RequestBody NewOrderRequest newOrder);
}

使用Feign

/**注入刚刚定义的OrderService*/
    @Autowired
    private OrderService orderService;

// 使用

List<Coffee> coffees = coffeeService.getAll();

// 传对象参数
NewOrderRequest orderRequest = NewOrderRequest.builder()
                .customer("Li Lei")
                .items(Arrays.asList("capuccino"))
                .build();
        Order order = orderService.create(orderRequest);

// 单个参数
Order order = orderService.getOrder(id);