4_feign声明式服务调用和断路器

男娘i 2022-04-13 13:47 138阅读 0赞

## 前言 ##

项目准备

> 1、创建项目feign-consumer  
> 2、继续使用之前的服务提供者hello-service

## 1、简单的声明式服务调用 ##

### 1.1、pom ###

<dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-eureka</artifactId>
          </dependency>
    
          <dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-feign</artifactId>
          </dependency>

<?xml version="1.0" encoding="UTF-8"?>
    <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.didispace</groupId>
       <artifactId>feign-consumer</artifactId>
       <version>0.0.1-SNAPSHOT</version>
       <packaging>jar</packaging>
    
       <name>feign-consumer</name>
       <description>Demo project for Spring Boot</description>
    
       <parent>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-parent</artifactId>
          <version>1.3.7.RELEASE</version>
          <relativePath/> 
       </parent>
    
       <properties>
          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
          <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
          <java.version>1.8</java.version>
       </properties>
    
       <dependencies>
          <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.springframework.boot</groupId>
             <artifactId>spring-boot-starter-actuator</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-feign</artifactId>
          </dependency>
    
       </dependencies>
    
       <dependencyManagement>
          <dependencies>
             <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Brixton.SR5</version>
                <type>pom</type>
                <scope>import</scope>
             </dependency>
          </dependencies>
       </dependencyManagement>
    
       <build>
          <plugins>
             <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
             </plugin>
          </plugins>
       </build>
    
    </project>

### 1.2、注解开启 spring cloud feign申明式服务调用功能 ###

@EnableFeignClients //开启声明式服务调用

@EnableFeignClients
    @EnableDiscoveryClient
    @SpringBootApplication
    public class ConsumerApplication { 
    
    
    
       public static void main(String[] args) { 
          SpringApplication.run(ConsumerApplication.class, args);
       }
    
    }

### 1.3、定义HelloService接口 ###

\#\#\#\# 通过@FeignClient 注解指定服务名称来绑定服务 \#\#\#\# 然后通过springMVc 注解绑定服务提供者提供的REST接口，和服务提供者中的url是一模一样哦

@FeignClient(name="HELLO-SERVICE")
    public interface HelloService { 
    
        @RequestMapping("/hello")
        String hello();
    
    }

### 1.4、Controller 通过调用上面的接口来实现从本客户端发起对hello-service服务接口的hello的调用 ###

//这里用来测试对feign客户端的调用
    @RestController
    public class ConsumerController { 
    
        @Autowired
        HelloService helloService;
    
        @RequestMapping(value = "/feign-consumer", method = RequestMethod.GET)
        public String helloConsumer() { 
            return helloService.hello();
        }
    
    }

### 1.5、同ribbon实现的服务消费一样，需要指定服务的注册中心 ###

spring.application.name=feign-consumer
    server.port=9001
    
    eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/

### 1.6、开始验证，浏览器中访问[http://localhost:9001/feign-consumer][http_localhost_9001_feign-consumer] ###

## 2、参数绑定 ##

### 2.1、为了验证参数绑定，再服务提供者中再添加一些方法 ###

@RestController
    public class HelloController { 
    
       private final Logger logger = Logger.getLogger(getClass());
    
       @Autowired
       private DiscoveryClient client;
    
       @RequestMapping(value = "/hello", method = RequestMethod.GET)
       public String hello() { 
    
          ServiceInstance instance = client.getLocalServiceInstance();
          logger.info("/hello, host:" + instance.getHost() + ", service_id:" + instance.getServiceId());
          return "Hello World";
       }
    
    
    
       @RequestMapping(value = "/hello1", method = RequestMethod.GET)
       String hello(@RequestParam("name") String name) { 
    
          return "hello" +name;
       }
    
       @RequestMapping(value = "/hello2", method = RequestMethod.GET)
       User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age){ 
          return  new User(name,age);
       }
    
       
    
       @RequestMapping(value = "/hello3", method = RequestMethod.POST)
       String hello(@RequestBody User user){ 
          return "hello"+user.getName()+","+user.getAge();
       }
    
    
    }

### 2.2、在声明式服务调用的service接口中添加如下， 同时要创建和上面一模一样的User类 ###

\#\#\#\# 注意点：下面注解中的value绝对不仅能为空，这是因为它和feign合作了

//绑定服务提供者，并使用spirngMvc 注解绑定具体REST接口
    @FeignClient(name="HELLO-SERVICE")
    public interface HelloService { 
    
        @RequestMapping("/hello")
        String hello();
    
    
        @RequestMapping(value = "/hello1", method = RequestMethod.GET)
        String hello(@RequestParam("name") String name) ;
    
        @RequestMapping(value = "/hello2", method = RequestMethod.GET)
        User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
    
        @RequestMapping(value = "/hello3", method = RequestMethod.POST)
        String hello(@RequestBody User user);
    
    
    }

### 2.3、Controller 调用声明式服务传参开始吧 ###

@RequestMapping(value = "/feign-consumer2", method = RequestMethod.GET)
    public String helloConsumer2() { 
        StringBuilder sb = new StringBuilder();
        sb.append(helloService.hello()).append("\n");
        sb.append(helloService.hello("DIDI")).append("\n");
        sb.append(helloService.hello("DIDI", 30)).append("\n");
        sb.append(helloService.hello(new User("DIDI", 30))).append("\n");
        return sb.toString();
    }

### 2.4、开始验证，浏览器中访问 ###

![WX20181129-171915@2x][WX20181129-171915_2x]

## 3、继承特性，解决User不同位置的问题 ##

#### 解释： ####

> 1、这个时候我们会发现，在声明式服务中的User和服务提供者中的User的内容一抹一样，但是位置却不是一样的，所以这样很不利于维护，因为修改了一处，还要继续去修改另外的一处。

--------------------

> 2、在声明式@FeginClient中提供的接口其实服务提供者也可以使用。所以，请看下面

### 3.1、创建一个maven项目 hello-service-api ###

#### 3.1.1 、pom.xml如下 ####

#### 3.1.2、将2中的User复制过来 ####

![NmaCx75pJBV9Q0h][]

#### 3.1.3、将声明式服务调用中的接口类HelloService 复制过来，还要做一番修改哦 ####

> 1、将头部前缀修改为refactor

--------------------

> 2、url路径也修改更名为hello4 5 6

@RequestMapping("/refactor")
    public interface HelloService { 
    
        @RequestMapping(value = "/hello4", method = RequestMethod.GET)
        String hello(@RequestParam("name") String name) ;
    
        @RequestMapping(value = "/hello5", method = RequestMethod.GET)
        User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
    
        @RequestMapping(value = "/hello6", method = RequestMethod.POST)
        String hello(@RequestBody User user);
    
    }

### 3.2、开始对服务提供者进行重构 ###

#### 3.2.1、在hellop-service项目pom.xml中引入hello-service-api的依赖,一定要记得对它进行mvn install ####

<dependency>
       <groupId>com.didispace</groupId>
       <artifactId>hello-service-api</artifactId>
       <version>0.0.1-SNAPSHOT</version>
    </dependency>

#### 3.2.2、2、重点来了，创建controller类基础上面的HelloService,没有必要在加@RequestMapping，但是其他的是一定要加的 ####

@RestController
    public class RefactorHelloController implements HelloService{ 
    
    
        public String hello(@RequestParam("name") String name) { 
    
            return "hello" +name;
        }
    
        public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age){ 
            return  new User(name,age);
        }
        
    
        public String hello(@RequestBody User user){ 
            return "hello"+user.getName()+","+user.getAge();
        }
    
    }

### 3.3、下面开始对声明式服务调用开始改造 ###

#### 3.3.1、引入pom依赖 ####

<dependency>
       <groupId>com.didispace</groupId>
       <artifactId>hello-service-api</artifactId>
       <version>0.0.1-SNAPSHOT</version>
    </dependency>

#### 3.3.2、绑定服务提供者，接口让他来继承HelloService，这样就保证了和服务提供者中的R EST是一致的了 ####

//绑定服务提供者
    @FeignClient(name="HELLO-SERVICE")
    public interface RefactorHelloService  extends HelloService { 
    
    }

#### 3.3.3、Controller开测 ####

//这里用来测试对feign客户端的调用
    @RestController
    public class ConsumerController { 
    
        @Autowired
        RefactorHelloService refactorHelloService;
    
        /** * 2、测试传参 */
    
        @RequestMapping(value = "/feign-consumer2", method = RequestMethod.GET)
        public String helloConsumer2() { 
            StringBuilder sb = new StringBuilder();
            sb.append(refactorHelloService.hello("DIDI")).append("\n");
            sb.append(refactorHelloService.hello("DIDI", 30)).append("\n");
            sb.append(refactorHelloService.hello(new User("DIDI", 30))).append("\n");
            return sb.toString();
        }
    }

#### 3.3.4、开始测试，浏览器访问 http://localhost:9001/feign-consumer2 成功 ####

![WX20181129-173326@2x][WX20181129-173326_2x]

## 4、服务降级配置，类似于断路器(使用3中的项目开发) ##

### 4.1、声明式服务调用项目中添加service ###

HelloServiceFallback，使它实现HelloService 用来作为当调用服务提供者失败后返回的内容

@Component
    public class HelloServiceFallback implements HelloService { 
    
    
        @Override
        public String hello(@RequestParam("name") String name) { 
            return "error";
        }
    
        @Override
        public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age) { 
            return new User("未知", 0);
        }
    
        @Override
        public String hello(@RequestBody User user) { 
            return "error";
        }
    }

### 4.2、@Feign 绑定服务的时候就开始，添加降级配置 ###

//绑定服务提供者，并使用spirngMvc 注解绑定具体REST接口
    @FeignClient(name="HELLO-SERVICE" ,fallback =HelloServiceFallBack.class )
    public interface HelloService { 
    
        @RequestMapping("/hello")
        String hello();
    
        @RequestMapping(value = "/hello1", method = RequestMethod.GET)
        String hello(@RequestParam("name") String name) ;
    
        @RequestMapping(value = "/hello2", method = RequestMethod.GET)
        User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
    
        @RequestMapping(value = "/hello3", method = RequestMethod.POST)
        String hello(@RequestBody User user);
    
    
    }

### 4.3、浏览器测试（不开启服务提供者） http://localhost:9001/feign-consumer2 ###

![WX20181129-173820@2x][WX20181129-173820_2x]

## [HealerJean-代码下载][HealerJean-] ##

![ContactAuthor][]

[http_localhost_9001_feign-consumer]: http://localhost:9001/feign-consumer
[WX20181129-171915_2x]: /images/20220413/d7ff278f1f7f4516abd207ca7ba496bf.png
[NmaCx75pJBV9Q0h]: /images/20220413/0b4b6e39e8c4410ab1723d4bb4c51a04.png
[WX20181129-173326_2x]: /images/20220413/fce5e868d3594cf9b59eddc13768a658.png
[WX20181129-173820_2x]: /images/20220413/6e9d13295d9c4f75a1f890a5b3e8ee9a.png
[HealerJean-]: https://github.com/HealerJean/com-hlj-springcloud/tree/master/4
[ContactAuthor]: /images/20220413/c035a2e136834ff194052cfcd1bc3cf6.png