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Spring Cloud 之Feign实现微服务之间相互请求

杨小羊_ba17 2022-11-09 阅读 34
spring bootjava后端springxmlJava编程语言



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/> <!-- lookup parent from repository -->
    </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/> <!-- lookup parent from repository -->
    </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/> <!-- lookup parent from repository -->
    </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：

Spring Cloud 之Feign实现微服务之间相互请求_spring boot


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。

Spring Cloud 之Feign实现微服务之间相互请求_spring_02


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。

Spring Cloud 之Feign实现微服务之间相互请求_后端_03

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。

Spring Cloud 之Feign实现微服务之间相互请求_java_04


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！


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