springcloud入门与实践

Spring Cloud 是一个基于 Spring Boot 的框架，专注于微服务架构下的常见问题，如服务发现、负载均衡、断路器、分布式配置、消息驱动的微服务等。以下是 Spring Cloud 的入门指南和实践示例。

1. 环境准备

首先，确保你已经安装了以下工具：

JDK 1.8+
Apache Maven 3.3+
Docker (可选，用于运行部分服务，如配置中心)

2. 创建一个简单的 Spring Cloud 项目

项目结构

我们将创建一个简单的 Spring Cloud 项目，包括配置服务、服务注册中心、服务提供者和服务消费者。项目结构如下：

spring-cloud-demo
├── config-server
├── eureka-server
├── service-provider
├── service-consumer
└── pom.xml

1. 创建父POM文件

首先，在项目根目录创建 pom.xml 文件，定义父POM：

pom.xml:

<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.example</groupId><artifactId>spring-cloud-demo</artifactId><version>1.0-SNAPSHOT</version><packaging>pom</packaging><modules><module>config-server</module><module>eureka-server</module><module>service-provider</module><module>service-consumer</module></modules><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>2021.0.3</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement>
</project>

2. 创建配置服务 (Config Server)

配置服务用于集中管理分布式系统中的配置文件。

config-server/pom.xml:

<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><parent><groupId>com.example</groupId><artifactId>spring-cloud-demo</artifactId><version>1.0-SNAPSHOT</version></parent><artifactId>config-server</artifactId><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-config-server</artifactId></dependency></dependencies>
</project>

config-server/src/main/resources/application.yml:

server:port: 8888spring:cloud:config:server:git:uri: https://github.com/your-repo/config-reposearch-paths: configmanagement:endpoints:web:exposure:include: "*"

config-server/src/main/java/com/example/config/ConfigServerApplication.java:

package com.example.config;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.config.server.EnableConfigServer;@SpringBootApplication
@EnableConfigServer
public class ConfigServerApplication {public static void main(String[] args) {SpringApplication.run(ConfigServerApplication.class, args);}
}

3. 创建服务注册中心 (Eureka Server)

服务注册中心用于服务的注册和发现。

eureka-server/pom.xml:

<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><parent><groupId>com.example</groupId><artifactId>spring-cloud-demo</artifactId><version>1.0-SNAPSHOT</version></parent><artifactId>eureka-server</artifactId><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-web</artifactId></dependency></dependencies>
</project>

eureka-server/src/main/resources/application.yml:

server:port: 8761eureka:client:register-with-eureka: falsefetch-registry: falseserver:wait-time-in-ms-when-sync-empty: 0

eureka-server/src/main/java/com/example/eureka/EurekaServerApplication.java:

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

4. 创建服务提供者 (Service Provider)

服务提供者提供具体的服务实现。

service-provider/pom.xml:

<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><parent><groupId>com.example</groupId><artifactId>spring-cloud-demo</artifactId><version>1.0-SNAPSHOT</version></parent><artifactId>service-provider</artifactId><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></dependencies>
</project>

service-provider/src/main/resources/application.yml:

server:port: 8080spring:application:name: service-providereureka:client:service-url:defaultZone: http://localhost:8761/eureka/

service-provider/src/main/java/com/example/provider/ServiceProviderApplication.java:

package com.example.provider;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;@SpringBootApplication
@EnableEurekaClient
public class ServiceProviderApplication {public static void main(String[] args) {SpringApplication.run(ServiceProviderApplication.class, args);}
}

service-provider/src/main/java/com/example/provider/controller/HelloController.java:

package com.example.provider.controller;import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;@RestController
public class HelloController {@GetMapping("/hello")public String sayHello(@RequestParam String name) {return "Hello, " + name;}
}

5. 创建服务消费者 (Service Consumer)

服务消费者调用服务提供者提供的服务。

service-consumer/pom.xml:

<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://www.m aaven.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>com.example</groupId><artifactId>spring-cloud-demo</artifactId><version>1.0-SNAPSHOT</version></parent><artifactId>service-consumer</artifactId><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></dependencies>
</project>

service-consumer/src/main/resources/application.yml:

server:port: 8081spring:application:name: service-consumereureka:client:service-url:defaultZone: http://localhost:8761/eureka/

service-consumer/src/main/java/com/example/consumer/ServiceConsumerApplication.java:

package com.example.consumer;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class ServiceConsumerApplication {public static void main(String[] args) {SpringApplication.run(ServiceConsumerApplication.class, args);}
}

service-consumer/src/main/java/com/example/consumer/client/HelloClient.java:

package com.example.consumer.client;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;@FeignClient(name = "service-provider")
public interface HelloClient {@GetMapping("/hello")String sayHello(@RequestParam(name = "name") String name);
}

service-consumer/src/main/java/com/example/consumer/controller/HelloController.java:

package com.example.consumer.controller;import com.example.consumer.client.HelloClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;@RestController
public class HelloController {private final HelloClient helloClient;public HelloController(HelloClient helloClient) {this.helloClient = helloClient;}@GetMapping("/hello")public String sayHello(@RequestParam String name) {return helloClient.sayHello(name);}
}

3. 构建和运行

首先，通过Maven构建项目。在项目根目录下运行以下命令：

mvn clean install

启动配置服务

进入 config-server 目录，运行以下命令启动配置服务：

mvn spring-boot:run

启动服务注册中心

进入 eureka-server 目录，运行以下命令启动服务注册中心：

mvn spring-boot:run

启动服务提供者

进入 service-provider 目录，运行以下命令启动服务提供者：

mvn spring-boot:run

启动服务消费者

进入 service-consumer 目录，运行以下命令启动服务消费者：

mvn spring-boot:run

如果一切正常，你应该可以在浏览器中访问 http://localhost:8081/hello?name=World，并看到以下输出：

Hello, World

4. 配置中心与负载均衡

你可以进一步配置配置中心以存储和分发配置文件，并在服务消费者中启用负载均衡，以在多个服务实例之间分发请求。

配置中心示例

在 config-repo 仓库中创建配置文件 service-provider.yml：

spring:application:name: service-provider
server:port: 8080

在 service-consumer.yml 文件中配置负载均衡：

spring:application:name: service-consumer
server:port: 8081eureka:client:service-url:defaultZone: http://localhost:8761/eureka/spring:cloud:loadbalancer:ribbon:OkToRetryOnAllOperations: true

总结

通过以上步骤，你已经成功创建了一个简单的 Spring Cloud 项目，包括配置服务、服务注册中心、服务提供者和服务消费者模块，并了解了如何使用 FeignClient 调用远程服务。Spring Cloud 提供了丰富的功能，如服务发现、负载均衡、断路器、分布式配置、消息驱动的微服务等，可以帮助你构建高性能、可伸缩的分布式系统。通过深入学习和实践，可以更好地掌握 Spring Cloud 的高级特性和最佳实践，满足实际项目的需求。