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This article introduces the knowledge of "how to use SpringCloud's OpenFeign for service invocation". Many people will encounter this dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Preface

Feign is a declarative Web service client that is interface-oriented. In other words, with Feign, you only need to create an interface and configure it with annotations to complete the interface binding to the micro-service provider.

When using RestTemplate, you need to specify the specific path of the service each time you invoke the service, and when you use it in multiple places at the same time, you have to write multiple times, which makes it difficult to maintain code redundancy, which can be avoided by openfeign.

1. Overview of OpenFeign1.1 and OpenFeign

1. What is it?

Feign is a declarative web service client that makes it easy to write a web service client by creating an interface and annotating it.

Source code address

two。 What can I do?

Feign is designed to make it easier to write Java Http clients.

When using Ribbon + RestTemplate, the previous service invocation uses RestTemplate's encapsulation of http requests to form a set of templated invocation methods. However, in the actual development, because there may be more than one call to the service dependency, often an interface will be called in multiple places, so it is usually necessary to encapsulate some client classes for each micro-service to wrap these invocations. Therefore, Feign makes further encapsulation on this basis, and it helps us to define and implement the definition of dependent service interfaces. Under the implementation of Feign, we only need to create an interface and configure it with annotations (in the past, Dao interfaces were marked with Mapper annotations, but now a Feign annotation is marked on a micro-service interface) to complete the interface binding to the service provider, which simplifies the development of automatically encapsulating the service invocation client when using Spring Cloud Ribbon.

Feign integrates Ribbon, uses Ribbon to maintain the service list information of Payment, and realizes the load balancing of the client through polling. Unlike Ribbon, Feign only needs to define the service binding interface and implements the service invocation elegantly and simply in a declarative way.

3. The difference between Feign and OpenFeign

FeignOpenFeignFeign is a lightweight restful Http service client in SpringCloud components. Feign has built-in Ribbon to do client-side load balancing to invoke services in the service registry. Feign is used by using Feign's annotations to define the interface, and by calling this interface, you can invoke the service of the service registry OpenFeign. SpringCloud supports SpringMVC annotations on the basis of Feign, such as @ RequestMapping, and so on. The @ FeignClient of OpenFeign can parse the interface under the @ RequestMapping annotation of SpringMVC, and implement the class by dynamic proxy, realizing the steps of load balancing and calling other services 1.2 and OpenFeign in the class.

1. Build Module

The name of Module is cloud-consumer-feign-order80.

two。 Change to POM

Cloud02 com.xiao 1.0-SNAPSHOT 4.0.0 cloud-consumer-feign-order80 org.springframework.cloud spring-cloud-starter-openfeign org.springframework.cloud spring-cloud-starter-netflix-eureka-client com.xiao cloud-api- Commons 1.0-SNAPSHOT org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-actuator org.springframework.boot spring-boot-devtools runtime true Org.projectlombok lombok true org.springframework.boot spring-boot-starter-test test

3. Change to YML

Server: port: 80eureka: client: register-with-eureka: false service-url: defaultZone: http://eureka7001.com:7001/eureka, http://eureka7002.com:7002/eureka

4. Main start

Import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication@EnableFeignClients / / Open OpenFeignpublic class OrderFeignMain80 {public static void main (String [] args) {SpringApplication.run (OrderFeignMain80.class,args);}}

@ EnableFeignClients turn on OpenFeign

5. PaymentFeignService interface

Import com.xiao.cloud.entities.CommonResult;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.stereotype.Component;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;@Component@FeignClient (value = "CLOUD-PAYMENT-SERVICE") / / use OpenFeignpublic interface PaymentFeignService {@ GetMapping ("/ payment/get/ {id}") public CommonResult getPaymentById (@ PathVariable ("id") Long id);}

@ FeignClient (value = "CLOUD-PAYMENT-SERVICE") uses OpenFeign.

6. Controller class

Import com.xiao.cloud.entities.CommonResult;import com.xiao.cloud.entities.Payment;import com.xiao.cloud.service.PaymentFeignService;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RestController;@RestController@Slf4jpublic class PaymentFeignController {@ Autowired private PaymentFeignService paymentFeignService GetMapping ("/ consumer/payment/get/ {id}") public CommonResult getPaymentById (@ PathVariable ("id") Long id) {return paymentFeignService.getPaymentById (id);}}

7. Test result

When we click Refresh many times, the port changes in turn between 8001 and 8002.

8. Small summary

1.3, timeout control 1.3.1, what is it?

The default Feign client only waits for one second, but it takes more than 1 second for the server to process. As a result, the Feign client does not want to wait and returns an error directly. To avoid this, sometimes we need to set the timeout control for the Feign client.

Open the configuration in the yml file.

1.3.2. Timeout error in modifying code settings

1. Modify the Controller of payment module 8001

Add the following code

GetMapping (value = "/ payment/feign/timeout") public String timeOUt () {try {Thread.sleep (3000);} catch (InterruptedException e) {e.printStackTrace ();} return ServerPort;}

two。 Modify the PaymentFeignService of the order module

Add the following code

GetMapping (value = "/ payment/feign/timeout") public String timeOUt ()

3. Modify the OrderFeignController of the order module

Add the following code

GetMapping (value = "/ consumer/payment/feign/timeout") public String timeOUt () {return paymentFeignService.timeOUt ();}

4. Test result

Directly invoke the exposed service interface of the payment module 8001 and pass the test.

If the call is made through the order module, a timeout error is reported.

1.3.3. Time-out configuration

Add the following code to the YML file of the order module

Ribbon: ReadTimeout: 8000 ConnectTimeout: 8000

1. Test result

The self-test passed.

1.4, log printing 1.4.1, what is it?

Feign provides log printing, and we can adjust the log level through configuration to understand the details of Http requests in Feign. Is to monitor and output the calls to the feign interface.

1.4.2, log level

NONE: by default, no logs are displayed

BASIC: only record request method, URL, response status code and execution time

HEADERS: in addition to the information defined in BASIC, there is also header information for requests and responses

FULL: in addition to the information defined in HEADERS, there is also the body and metadata of the request and response.

1.4.3. How to turn on log printing

1. Write a log configuration class

Import feign.Logger;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class FeignConfig {@ Bean Logger.Level feignLoggerLevel () {return Logger.Level.FULL;}}

two。 Make relevant configuration in the YML file

Server: port: 80eureka: client: register-with-eureka: false service-url: defaultZone: http://eureka7001.com:7001/eureka, http://eureka7002.com:7002/eurekaribbon: ReadTimeout: 8000 ConnectTimeout: 8000logging: level: com.atguigu.springcloud.service.PaymentFeignService: debug

3. Test result

4. Packet structure diagram

This is the end of the content of "how to use SpringCloud's OpenFeign to make service calls". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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