如何在Feign這個(gè)組件里面,Feign這個(gè)組件里面使用Hystrix,也就是Feign如何搭配Hystrix,我們可以先來看一下Feign這個(gè)組件,看他都依賴了哪些組件,我們pom文件里面引的是spring-cloud-starter-feign,你看到這里面,這里面其實(shí)有一個(gè)feignhystrix,你看他引導(dǎo)了hystrix-core,說明他里面已經(jīng)集成好了hystrix,我們不需要單獨(dú)的引入hystrix包,可以直接來用,那么使用的時(shí)候,怎么用呢,第一你需要配置一下,feign.hystrix,注意是沒有提示的,所以我們寫的時(shí)候得注意一下,不要寫錯(cuò)了,feign.hystrix.enabled=true需要首先做這么一個(gè)配置,然后我們再來看一下productClient,這塊代碼寫到哪兒,這段代碼寫到product服務(wù)里面,這里提供一個(gè)jar包,我們只是引用而已,這里面怎么使用Hystrix呢,你不能加一個(gè)HystrixCommand注解了,這邊都是interface,不一樣了,那這里面怎么用呢,@FeignClient這里面有一個(gè)參數(shù),可以傳,叫做fallback,fallback里面的內(nèi)容要填一個(gè)class,還沒有創(chuàng)建的一個(gè)class@Component public class ProductClientFallback implements ProductClient {@Overridepublic List<ProductInfo> listForOrder(@RequestBody List<String> productIdList) {return null;}}實(shí)現(xiàn)ProductClient,把他里面的方法都給實(shí)現(xiàn)了,如果產(chǎn)生服務(wù)降級的話呢,比如產(chǎn)生服務(wù)降級的話,那么他就會(huì)訪問到這兒來,返回一個(gè)null,我們先返回一個(gè)null,這個(gè)class要加一個(gè)注解,這個(gè)是要注意的一點(diǎn),很容易被大家忽略掉,注意看一下他的用法,在FeignClient里面加一個(gè)fallback的字段,指定如果產(chǎn)生服務(wù)降級的話,那么訪問到的實(shí)際的方法,接下來我們啟動(dòng)order的服務(wù),我們怎么觀察服務(wù)降級呢,如果是出現(xiàn)服務(wù)降級的話,那么返回的結(jié)果應(yīng)該是null,你看一下我們的ProductClient,看一下我們的client,看一下這里面的代碼@Component public class ProductClientFallback implements ProductClient {@Overridepublic List<ProductInfo> listForOrder(@RequestBody List<String> productIdList) {return null;}}加了@Component這個(gè)注解,我們希望class載入到Spring的容器里面,那么問題來了,我問一下大家,這塊代碼到底是在哪個(gè)項(xiàng)目里面運(yùn)行的,這塊代碼雖然寫是寫在Product項(xiàng)目,是order服務(wù)里面來引用,這塊其實(shí)就可以理解為是order里面的一塊代碼了,他已經(jīng)在order項(xiàng)目里面了,這就是一片代碼,所以運(yùn)行的時(shí)候呢,他肯定是在order里面來運(yùn)行的,那么為什么不起作用呢,這是因?yàn)槲覀兊膯?dòng)類里面沒有掃描到https://blog.csdn.net/huanxianglove/article/details/80914504@SpringCloudApplication @EnableFeignClients public class OrderApplication {public static void main(String[] args) {// Spring應(yīng)用啟動(dòng)起來SpringApplication.run(OrderApplication.class,args);}}我們要配置一下掃描,現(xiàn)在已經(jīng)成功啟動(dòng)了,我們使用postman下一個(gè)但試一試localhost:8010/createOrder[{productId: "00000",productName: "太陽面",productPrice: null,productStock: null,productDescription: null,productIcon: null,productStatus: null,categoryType: null,createTime: null,updateTime: null} ]可以看到productId就是"00000",我們product壓根就沒有啟動(dòng),他就是null,所以證明我們的服務(wù)降級已經(jīng)起作用了,因?yàn)槭莕ull,所以報(bào)了一個(gè)空指針,他并沒有像之前一樣的,報(bào)找不到這個(gè)服務(wù),我們再來回顧一下,Feign組件里面使用Hystrix,第一點(diǎn)就是配置,這一點(diǎn)可能很多人會(huì)忘記feign.hystrix.enabled=true這一點(diǎn)特別要注意,你這個(gè)地方配錯(cuò)了就不生效了,還有一個(gè)地方就是啟動(dòng)類,包掃描,因?yàn)槲覀兪褂玫氖荘roduct服務(wù),所以你得把它配置進(jìn)來,掃描得到,；=另外就是降級fallback的這個(gè)類,這上面注解不要忘記了,這三點(diǎn)大家切記 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.learn</groupId><artifactId>order</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><parent><groupId>cn.learn</groupId><artifactId>microcloud02</artifactId><version>0.0.1</version></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><java.version>1.8</java.version><thymeleaf.version>3.0.9.RELEASE</thymeleaf.version><thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-amqp</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-stream-rabbit</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-hystrix</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-feign</artifactId></dependency></dependencies><!-- 這個(gè)插件,可以將應(yīng)用打包成一個(gè)可執(zhí)行的jar包 --><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project> server.port=8010eureka.client.serviceUrl.defaultZone=http://admin:1234@10.40.8.152:8761/eurekaspring.application.name=order eureka.instance.prefer-ip-address=true eureka.instance.instance-id=${spring.application.name}:${spring.cloud.client.ipAddress}:${spring.application.instance_id:${server.port}}spring.rabbitmq.host=59.110.158.145 spring.rabbitmq.username=guest spring.rabbitmq.password=guest spring.rabbitmq.port=5672spring.cloud.stream.bindings.myMessage.group=order spring.cloud.stream.bindings.myMessage.content-type=application/jsonhystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=1000 hystrix.command.getProductInfoList.execution.isolation.thread.timeoutInMilliseconds=5000feign.hystrix.enabled=true package com.learn.client;import java.util.List;import org.springframework.cloud.netflix.feign.FeignClient; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody;import com.learn.dto.ProductInfo;@FeignClient(name = "product",fallback = ProductClientFallback.class) public interface ProductClient {@PostMapping("/listForOrder")public List<ProductInfo> listForOrder(@RequestBody List<String> productIdList);} package com.learn.client;import java.util.ArrayList; import java.util.List;import org.springframework.stereotype.Component; import org.springframework.web.bind.annotation.RequestBody;import com.learn.dto.ProductInfo;@Component public class ProductClientFallback implements ProductClient {@Overridepublic List<ProductInfo> listForOrder(@RequestBody List<String> productIdList) {ProductInfo p = new ProductInfo();p.setProductId("00000");p.setProductName("太陽面");List<ProductInfo> list = new ArrayList<ProductInfo>();list.add(p);return list;}} package com.learn.controller;import java.util.Arrays; import java.util.List;import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController;import com.learn.client.ProductClient; import com.learn.dto.ProductInfo;@RestController public class OrderFeignController {@Autowiredprivate ProductClient productClient;@GetMapping("/createOrder")public List<ProductInfo> listForOrder() {return this.productClient.listForOrder(Arrays.asList("1111"));}} package com.learn;import org.springframework.boot.SpringApplication; import org.springframework.cloud.client.SpringCloudApplication; import org.springframework.cloud.netflix.feign.EnableFeignClients;//@SpringBootApplication //@EnableRabbit //@EnableEurekaClient //@EnableCircuitBreaker @SpringCloudApplication @EnableFeignClients public class OrderApplication {public static void main(String[] args) {// Spring應(yīng)用啟動(dòng)起來SpringApplication.run(OrderApplication.class,args);}}

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