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1. feign自訂Configuration和root 容器有效隔離。
- 用@Configuration註解
- 不能在主@ComponentScan (or @SpringBootApplication)範圍內，從其包名上分離
- 注意避免包掃描重疊，最好的方法是明確的指定包名
2. Spring Cloud Netflix 提供了預設的Bean類型:
- Decoder feignDecoder: ResponseEntityDecoder (which wraps a SpringDecoder)
- Encoder feignEncoder: SpringEncoder
- Logger feignLogger: Slf4jLogger
- Contract feignContract: SpringMvcContract
- Feign.Builder feignBuilder: HystrixFeign.Builder
3. Spring Cloud Netflix沒有提供預設值，但仍然可以在feign上下文配置中建立：
- Logger.Level
- Retryer
- ErrorDecoder
- Request.Options
- Collection
4. 自訂feign的訊息編碼解碼器：
不要在如下代碼中getObject方法內new 對象，外部會頻繁調用getObject方法。
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ObjectFactory<HttpMessageConverters> messageConvertersObjectFactory = new ObjectFactory<HttpMessageConverters>() {
@Override
public HttpMessageConverters getObject() throws BeansException {
return httpMessageConverters;
}
}; |
5. 注意測試環境和生產環境，注意正確使用feign記錄層級。6. apacheHttpclient或者其他client的正確配置：
- apacheHttpclient自訂配置放在spring root context，不要在FeignContext，否則不會起作用。
- apacheHttpclient 串連池配置合理地串連和其他參數
7. Feign配置
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#Hystrix支援，如果為true，hystrix庫必須在classpath中
feign.hystrix.enabled=false
#請求和響應GZIP壓縮支援
feign.compression.request.enabled=true
feign.compression.response.enabled=true
#支援壓縮的mime types
feign.compression.request.enabled=true
feign.compression.request.mime-types=text/xml,application/xml,application/json
feign.compression.request.min-request-size=2048 # 日誌支援
logging.level.project.user.UserClient: DEBUG |
8. Logger.Level支援
必須為每一個Feign Client配置來告訴Feign如何輸出日誌，可選：
- NONE, No logging (DEFAULT).
- BASIC, Log only the request method and URL and the response status code and execution time.
- HEADERS, Log the basic information along with request and response headers.
- FULL, Log the headers, body, and metadata for both requests and responses.
9. FeignClient.fallback 正確的使用方法
配置的fallback class也必須在FeignClient Configuration中執行個體化，否則會報
java.lang.IllegalStateException: No fallback instance of type class異常。
例子：
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@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
public interface HystrixClient {
@RequestMapping(method = RequestMethod.GET, value = "/hello")
Hello iFailSometimes();
} public class HystrixClientFallback implements HystrixClient {
@Override
public Hello iFailSometimes() {
return new Hello("fallback");
}
} @Configuration
public class FooConfiguration {
@Bean
@Scope("prototype")
public Feign.Builder feignBuilder() {
return Feign.builder();
}
@Bean
public HystrixClientFallback fb(){
return new HystrixClientFallback();
}
} |
10. 使用Feign Client 和@RequestMapping時，注意事項
當前工程中有和Feign Client中一樣的Endpoint時，Feign Client的類上不能用@RequestMapping註解否則，當前工程該endpoint http請求且使用accpet時會報404.
下面的例子：
有一個 Controller
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@RestController
@RequestMapping("/v1/card")
public class IndexApi { @PostMapping("balance")
@ResponseBody
public Info index() {
Info.Builder builder = new Info.Builder();
builder.withDetail("x", 2);
builder.withDetail("y", 2);
return builder.build();
}
} |
有一個Feign Client
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@FeignClient(
name = "card",
url = "http://localhost:7913",
fallback = CardFeignClientFallback.class,
configuration = FeignClientConfiguration.class
)
@RequestMapping(value = "/v1/card")
public interface CardFeignClient { @RequestMapping(value = "/balance", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)
Info info(); } |
if @RequestMapping is used on class, when invoke http /v1/card/balance, like this :
如果 @RequestMapping註解被用在FeignClient類上，當像如下代碼請求/v1/card/balance時，注意有Accept header：
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Content-Type: application/json
Accept: application/json POST http://localhost:7913/v1/card/balance |
那麼會返回 404。
如果不包含Accept header時請求，則是OK：
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Content-Type:application/json
POST http://localhost:7913/v1/card/balance |
或者像下面不在Feign Client上使用@RequestMapping註解,請求也是ok，無論是否包含Accept:
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@FeignClient(
name = "card",
url = "http://localhost:7913",
fallback = CardFeignClientFallback.class,
configuration = FeignClientConfiguration.class
) public interface CardFeignClient { @RequestMapping(value = "/v1/card/balance", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)
Info info(); } |
Spring Cloud Feign 使用方法與效能最佳化
