@Feignclient comments and parameters

@FeignClient Notes and parameters

One 、FeignClient annotation

FeignClient The annotation is @Target(ElementType.TYPE) modification , Express FeignClient The purpose of annotation is on the interface

@FeignClient(name = "github-client", url = "https://api.github.com", configuration = GitHubExampleConfig.class)
public interface GitHubClient {
    
    @RequestMapping(value = "/search/repositories", method = RequestMethod.GET)
    String searchRepo(@RequestParam("q") String queryStr);
}

After declaring the interface , In the code through @Resource It can be used after injection [email protected] The common attributes of tags are as follows ：

name： Appoint FeignClient The name of , If the project is used Ribbon,name The property will be used as the name of the microservice , For service discovery 
url: url Generally used for debugging , Can be specified manually @FeignClient The address of the call 
decode404: Happen when http 404 When it's wrong , If the word segment true, Would call decoder decode , Otherwise throw FeignException
configuration: Feign Configuration class , You can customize Feign Of Encoder、Decoder、LogLevel、Contract
fallback:  Defines fault-tolerant handling classes , When the call to the remote interface fails or times out , The fault-tolerant logic of the corresponding interface is invoked ,fallback The specified class must be implemented @FeignClient Tagged interface 
fallbackFactory:  Factory , Used to generate fallback Class example , With this property we can implement fault tolerance logic common to each interface , Reduce duplicate code 
path:  Define the current FeignClient Unified prefix of 

@FeignClient(name = "github-client",
        url = "https://api.github.com",
        configuration = GitHubExampleConfig.class,
        fallback = GitHubClient.DefaultFallback.class)
public interface GitHubClient {
    
    @RequestMapping(value = "/search/repositories", method = RequestMethod.GET)
    String searchRepo(@RequestParam("q") String queryStr);

    /** *  Fault tolerant processing class , When the call fails , Simply return an empty string  */
    @Component
    public class DefaultFallback implements GitHubClient {
    
        @Override
        public String searchRepo(@RequestParam("q") String queryStr) {
    
            return "";
        }
    }

}
// In the use of fallback Attribute , Need to use @Component annotation , Guarantee fallback Class quilt Spring The container scans to ,GitHubExampleConfig The contents are as follows ：
@Configuration
public class GitHubExampleConfig {
    
    @Bean
    Logger.Level feignLoggerLevel() {
    
        return Logger.Level.FULL;
    }
}

In the use of FeignClient when ,Spring Will press name Create different ApplicationContext, Through different Context To isolate FeignClient Configuration information , When using configuration classes , You can't put configuration classes in Spring App Component scan In the path of , otherwise , The configuration class will be for all FeignClient take effect .

Two 、Feign Client and @RequestMapping
There are and in the current project Feign Client In the same way Endpoint when ,Feign Client You can't use @RequestMapping Note otherwise , The current project should endpoint http Request and use accpet It will be reported in time 404
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();
    }

}

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 Annotations are used in FeignClient Class , When code requests like /v1/card/balance when , Pay attention to it Accept header：

Content-Type:application/json
Accept:application/json

POST http://localhost:7913/v1/card/balance
So it will return 404.

If not Accept header Ask for , It is OK：

Content-Type:application/json
POST http://localhost:7913/v1/card/balance
Or like it's not down here Feign Client Upper use @RequestMapping annotation , So is the request ok, Whether or not it contains 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();

}

3、 ... and 、Feign Request timeout problem
Hystrix The default timeout is 1 second , If there is no response beyond this time , Will enter fallback Code . The first request is often slow （ because Spring The lazy loading mechanism of , To instantiate some classes ）, This response time may be greater than 1 The second
There are three solutions , With feign For example .
Method 1
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 5000
The configuration is to let Hystrix The timeout for is changed to 5 second
Method 2
hystrix.command.default.execution.timeout.enabled: false
This configuration , Used to disable Hystrix Timeout for
Method 3
feign.hystrix.enabled: false
This configuration , It is used to disable feign Of hystrix. It's not possible to do this unless there are some special situations , It is not recommended to use .
See ：http://www.itmuch.com/spring-cloud-sum-feign/