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1. feign自定义Configuration和root 容器有效隔离。
- 用@Configuration注解
- 不能在主@ComponentScan (or @SpringBootApplication)范围内，从其包名上分离
- 注意避免包扫描重叠，最好的方法是明确的指定包名
2. Spring Cloud Netflix 提供了默认的Bean类型:
- 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没有提供默认值，但仍然可以在feign上下文配置中创建：
- Logger.Level
- Retryer
- ErrorDecoder
- Request.Options
- Collection<RequestInterceptor>
4. 自定义feign的消息编码解码器：
不要在如下代码中getObject方法内new 对象，外部会频繁调用getObject方法。
ObjectFactory<HttpMessageConverters> messageConvertersObjectFactory = new ObjectFactory<HttpMessageConverters>() {
@Override
public HttpMessageConverters getObject() throws BeansException {
return httpMessageConverters;
}
};
5. 注意测试环境和生产环境，注意正确使用feign日志级别。
6. apacheHttpclient或者其他client的正确配置：
- apacheHttpclient自定义配置放在spring root context，不要在FeignContext，否则不会起作用。
- apacheHttpclient 连接池配置合理地连接和其他参数
7. Feign配置
#Hystrix支持，如果为true，hystrix库必须在classpath中
feign.hystrix.enabled=false
#请求和响应GZIP压缩支持
feign.compression.request.enabled=true
feign.compression.response.enabled=true
#支持压缩的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
# 日志支持
logging.level.project.user.UserClient: DEBUG
8. Logger.Level支持
必须为每一个Feign Client配置来告诉Feign如何输出日志，可选：
- 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 正确的使用方法
配置的fallback class也必须在FeignClient Configuration中实例化，否则会报
java.lang.IllegalStateException: No fallback instance of type class异常。
例子：
@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时，注意事项
当前工程中有和Feign Client中一样的Endpoint时，Feign Client的类上不能用@RequestMapping注解否则，当前工程该endpoint http请求且使用accpet时会报404.
下面的例子：
有一个 Controller
@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();
}
}
有一个Feign Client
@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注解被用在FeignClient类上，当像如下代码请求/v1/card/balance时，注意有Accept header：
Content-Type:application/json
Accept:application/json
POST http://localhost:7913/v1/card/balance
那么会返回 404。
如果不包含Accept header时请求，则是OK：
Content-Type:application/json
POST http://localhost:7913/v1/card/balance
或者像下面不在Feign Client上使用@RequestMapping注解,请求也是ok，无论是否包含Accept:
@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();
}
