Spring Cloud 之Feign实现微服务之间相互请求

系统管理员 2022-12-15 08:46 150阅读 0赞

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## Spring Cloud 之Feign实现微服务之间相互请求 ##

创建第一个Spring Boot项目作为注册中心。

`pom.xml`如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.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>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</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>

`application.yml`如下：

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
        register-with-eureka: false
      server:
        enable-self-preservation: false
    
    spring:
      application:
        name: eureka
    
    server:
      port: 8761

启动类：

package com.kaven.eureka;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    @SpringBootApplication
    @EnableEurekaServer
    public class EurekaApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(EurekaApplication.class, args);
        }
    }

注解`@EnableEurekaServer`不要忘记加上。

创建第二个Spring Boot项目作为第一个微服务。  
`pom.xml`如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.kaven</groupId>
        <artifactId>server</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>server</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</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>

`application.yml`如下：

spring:
      application:
        name: server
    
    server:
      port: 8001
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/

启动类：

package com.kaven.server;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    public class ServerApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(ServerApplication.class, args);
        }
    }

注解`@EnableDiscoveryClient`不要忘记加上。

再写一个接口（用于被其他微服务请求）：

package com.kaven.server.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class MessageServerController { 
    
        @GetMapping("/getMessage")
        public String getMessage(){ 
            return "hello , Jack";
        }
    }

创建第三个Spring Boot项目作为第二个微服务。  
`pom.xml`如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.kaven</groupId>
        <artifactId>client</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>client</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</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>

`application.yml`如下：

spring:
      application:
        name: client
    
    server:
      port: 8002
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/

启动类：

package com.kaven.client;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ClientApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(ClientApplication.class, args);
        }
    }

注解`@EnableDiscoveryClient`、`@EnableFeignClients`不要忘记加上。

再写一个FeignClient，即ServerClient接口，并且有一个内部类ServerClientFallback实现它：

package com.kaven.client.client;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.context.annotation.Bean;
    import org.springframework.stereotype.Component;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.client.RestTemplate;
    
    @Component
    @FeignClient(name = "server" , fallback = ServerClient.ServerClientFallback.class)
    public interface ServerClient { 
    
        @GetMapping("/getMessage")
        String getMessage();
    
        @Component
        class ServerClientFallback implements ServerClient{ 
    
            @Override
            public String getMessage() { 
                return "接口请求失败";
            }
        }
    }

这个ServerClient接口就是将Server服务的接口定义成一个个方法，而ServerClientFallback类实现该接口，就相当于是一种容错机制，当接口请求不成功时，就会调用ServerClientFallback类这里的实现，从注解`@FeignClient(name = "server" , fallback = ServerClient.ServerClientFallback.class)`也可以看出来。

再写一个接口用来请求第一个微服务的接口（借助ServerClient）：

package com.kaven.client.controller;
    
    import com.kaven.client.client.ServerClient;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class MessageController { 
    
        @Autowired
        private ServerClient serverClient;
    
        @GetMapping("/getMessage")
        public String getMessage(){ 
    
            String message = serverClient.getMessage();
            return "get: "+message;
        }
    }

访问`http://localhost:8761/`，可以得到如下图所示的界面：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70]  
可以发现两个微服务已经注册上去了，发出警告的原因是因为注册中心关闭了自我保护模式。

访问`http://localhost:8001/getMessage`，即第一个微服务的接口，可以得到如下图所示的界面。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 1]  
再来访问`http://localhost:8002/getMessage`，即第二个微服务的接口，可以得到如下图所示的界面，这说明Feign应用成功了。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 2]

该接口会通过Feign来请求第一个微服务的接口，以便获取数据。

修改一下ServerClient接口以便测试一下server服务请求不成功的情况。

package com.kaven.client.client;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.context.annotation.Bean;
    import org.springframework.stereotype.Component;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.client.RestTemplate;
    
    @Component
    @FeignClient(name = "server" , fallback = ServerClient.ServerClientFallback.class)
    public interface ServerClient { 
    
        @GetMapping("/getMsg")
        String getMessage();
    
        @Component
        class ServerClientFallback implements ServerClient{ 
    
            @Override
            public String getMessage() { 
                return "接口请求失败";
            }
        }
    }

就是将`@GetMapping("/getMessage")`改成了`@GetMapping("/getMsg")`，这样就不可能请求成功了。

配置文件也要修改：

spring:
      application:
        name: client
    
    server:
      port: 8002
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
    feign:
      hystrix:
        enabled: true

下面的配置是表示Feign开启容错机制，之后的博客会介绍Hystrix组件。

feign:
      hystrix:
        enabled: true

再来访问`http://localhost:8002/getMessage`，可以得到如下图所示的界面，这说明我们的容错机制是有效的。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 3]  
Spring Cloud使用Feign实现微服务之间相互请求就介绍到这里。

写博客是博主记录自己的学习过程，如果有错误，请指正，谢谢！

[Link 1]: https://kaven.blog.csdn.net/article/details/109063924
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