写作时间：2019-11-15
实现目标：Spring Cloud Netflix
涉及知识：微服务架构解决方案

【概述】

Spring Cloud 是一个相对比较新的微服务框架，2016 才推出 1.0 的 Release 版本. 但是其更新特别快，几乎每 1-2 个月就有一次更新，虽然 Spring Cloud 时间最短, 但是相比 Dubbo 等 RPC 框架, Spring Cloud 提供的全套的分布式系统解决方案。

Spring Cloud 为开发者提供了在分布式系统（配置管理，服务发现，熔断，路由，微代理，控制总线，一次性 Token，全居琐，Leader 选举，分布式 Session，集群状态）中快速构建的工具，使用 Spring Cloud 的开发者可以快速的启动服务或构建应用、同时能够快速和云平台资源进行对接。

【创建统一的依赖管理】

创建一个工程名为 hello-spring-cloud-dependencies 的项目，pom.xml 配置文件如下：

<?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 http://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>2.0.2.RELEASE</version>
    </parent>

    <groupId>com.yan</groupId>
    <artifactId>hello-spring-cloud-dependencies</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <properties>
        <!-- Environment Settings -->
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <!-- Spring Settings -->
        <spring-cloud.version>Finchley.RC1</spring-cloud.version>
    </properties>

    <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>
            <!-- Compiler 插件, 设定 JDK 版本 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <showWarnings>true</showWarnings>
                </configuration>
            </plugin>

            <!-- 打包 jar 文件时，配置 manifest 文件，加入 lib 包的 jar 依赖 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <archive>
                        <addMavenDescriptor>false</addMavenDescriptor>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <configuration>
                            <archive>
                                <manifest>
                                    <!-- Add directory entries -->
                                    <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                                    <addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
                                    <addClasspath>true</addClasspath>
                                </manifest>
                            </archive>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

            <!-- resource -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
            </plugin>

            <!-- install -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-install-plugin</artifactId>
            </plugin>

            <!-- clean -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-clean-plugin</artifactId>
            </plugin>

            <!-- ant -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-antrun-plugin</artifactId>
            </plugin>

            <!-- dependency -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
            </plugin>
        </plugins>

        <pluginManagement>
            <plugins>
                <!-- Java Document Generate -->
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-javadoc-plugin</artifactId>
                    <executions>
                        <execution>
                            <phase>prepare-package</phase>
                            <goals>
                                <goal>jar</goal>
                            </goals>
                        </execution>
                    </executions>
                </plugin>

                <!-- YUI Compressor (CSS/JS压缩) -->
                <plugin>
                    <groupId>net.alchim31.maven</groupId>
                    <artifactId>yuicompressor-maven-plugin</artifactId>
                    <version>1.5.1</version>
                    <executions>
                        <execution>
                            <phase>prepare-package</phase>
                            <goals>
                                <goal>compress</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
                        <encoding>UTF-8</encoding>
                        <jswarn>false</jswarn>
                        <nosuffix>true</nosuffix>
                        <linebreakpos>30000</linebreakpos>
                        <force>true</force>
                        <includes>
                            <include>**/*.js</include>
                            <include>**/*.css</include>
                        </includes>
                        <excludes>
                            <exclude>**/*.min.js</exclude>
                            <exclude>**/*.min.css</exclude>
                        </excludes>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>

        <!-- 资源文件配置 -->
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <excludes>
                    <exclude>**/*.java</exclude>
                </excludes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
            </resource>
        </resources>
    </build>

    <repositories>
        <repository>
            <id>aliyun-repos</id>
            <name>Aliyun Repository</name>
            <url>http://maven.aliyun.com/nexus/content/groups/public</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>

        <repository>
            <id>sonatype-repos</id>
            <name>Sonatype Repository</name>
            <url>https://oss.sonatype.org/content/groups/public</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>sonatype-repos-s</id>
            <name>Sonatype Repository</name>
            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
            <releases>
                <enabled>false</enabled>
            </releases>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>

        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

    <pluginRepositories>
        <pluginRepository>
            <id>aliyun-repos</id>
            <name>Aliyun Repository</name>
            <url>http://maven.aliyun.com/nexus/content/groups/public</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>
</project>
  • parent：继承了 Spring Boot 的 Parent，表示我们是一个 Spring Boot 工程
  • package：pom，表示该项目仅当做依赖项目，没有具体的实现代码
  • spring-cloud-dependencies：在 properties 配置中预定义了版本号为 Finchley.RC1 ，表示我们的 Spring Cloud 使用的是 F 版
  • build：配置了项目所需的各种插件
  • repositories：配置项目下载依赖时的第三方库

在实际开发中，我们所有的项目都会依赖这个 dependencies 项目，整个项目周期中的所有第三方依赖的版本也都由该项目进行管理。

【服务注册与发现】

我们需要用的组件是 Spring Cloud Netflix 的Eureka，Eureka 是一个服务注册和发现模块

POM

<?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>

    <parent>
        <groupId>com.yan</groupId>
        <artifactId>hello-spring-cloud-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>hello-spring-cloud-eureka</artifactId>
    <packaging>jar</packaging>

    <dependencies>
        <!-- Spring Boot Begin -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Spring Boot End -->

        <!-- Spring Cloud Begin -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <!-- Spring Cloud End -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.yan.hello.spring.cloud.eureka.EurekaApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Application

启动一个服务注册中心，只需要一个注解 @EnableEurekaServer

package com.yan.hello.spring.cloud.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);
    }
}

application.yml

Eureka 是一个高可用的组件，它没有后端缓存，每一个实例注册之后需要向注册中心发送心跳（因此可以在内存中完成），在默认情况下 Erureka Server 也是一个 Eureka Client ,必须要指定一个 Server。

spring:
  application:
    name: hello-spring-cloud-eureka

server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

通过 eureka.client.registerWithEureka:false 和 fetchRegistry:false 来表明自己是一个 Eureka Server.

【创建服务提供者】

POM

<?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>

    <parent>
        <groupId>com.yan</groupId>
        <artifactId>hello-spring-cloud-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>hello-spring-cloud-service-admin</artifactId>
    <packaging>jar</packaging>

    <dependencies>
        <!-- Spring Boot Begin -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Spring Boot End -->

        <!-- Spring Cloud Begin -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <!-- Spring Cloud End -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.yan.hello.spring.cloud.service.admin.ServiceAdminApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Application

通过注解 @EnableEurekaClient 表明自己是一个 Eureka Client.

package com.yan.hello.spring.cloud.service.admin;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

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

application.yml

spring:
  application:
    name: hello-spring-cloud-service-admin

server:
  port: 8762

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

Controller

package com.yan.hello.spring.cloud.service.admin.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AdminController {

    @Value("${server.port}")
    private String port;

    @GettMapping("/hi")
    public String sayHi(@RequestParam(value = "message") String message) {
        return String.format("Hi，your message is : %s i am from port : %s", message, port);
    }
}

【 创建服务消费者（Feign）】

Feign简介

Feign 是一个声明式的伪 Http 客户端，它使得写 Http 客户端变得更简单。使用 Feign，只需要创建一个接口并注解。

POM

<?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>

    <parent>
        <groupId>com.yan</groupId>
        <artifactId>hello-spring-cloud-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>hello-spring-cloud-web-admin-feign</artifactId>
    <packaging>jar</packaging>

    <dependencies>
        <!-- Spring Boot Begin -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Spring Boot End -->

        <!-- Spring Cloud Begin -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!-- Spring Cloud End -->

        <!-- 解决 thymeleaf 模板引擎一定要执行严格的 html5 格式校验问题 -->
        <dependency>
            <groupId>net.sourceforge.nekohtml</groupId>
            <artifactId>nekohtml</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.yan.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Application

通过 @EnableFeignClients 注解开启 Feign 功能

package com.yan.hello.spring.cloud.web.admin.feign;

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 WebAdminFeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(WebAdminFeignApplication.class, args);
    }
}

application.yml

spring:
  application:
    name: hello-spring-cloud-web-admin-feign
  thymeleaf:
    cache: false
    mode: LEGACYHTML5
    encoding: UTF-8
    servlet:
      content-type: text/html

server:
  port: 8765

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

Configuration

配置注入 RestTemplate 的 Bean，并通过 @LoadBalanced 注解表明开启负载均衡功能

package com.yan.hello.spring.cloud.web.admin.ribbon.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfiguration {

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

创建测试用的 接口和Controller

package com.yan.hello.spring.cloud.web.admin.feign.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "hello-spring-cloud-service-admin")
public interface AdminService {

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam(value = "message") String message);
}

package com.yan.hello.spring.cloud.web.admin.feign.controller;

import com.yan.hello.spring.cloud.web.admin.feign.service.AdminService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AdminController {

    @Autowired
    private AdminService adminService;

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam String message) {
        return adminService.sayHi(message);
    }
}

Feign 中使用熔断器

Feign 是自带熔断器的，但默认是关闭的。需要在配置文件中配置打开它，在配置文件增加以下代码：

feign:
  hystrix:
    enabled: true

增加 fallback 指定类

package com.yan.hello.spring.cloud.web.admin.feign.service;

import com.yan.hello.spring.cloud.web.admin.feign.service.hystrix.AdminServiceHystrix;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "hello-spring-cloud-service-admin", fallback = AdminServiceHystrix.class)
public interface AdminService {

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam(value = "message") String message);
}

创建熔断器类并实现对应的 Feign 接口

package com.yan.hello.spring.cloud.web.admin.feign.service.hystrix;

import com.yan.hello.spring.cloud.web.admin.feign.service.AdminService;
import org.springframework.stereotype.Component;

@Component
public class AdminServiceHystrix implements AdminService {

    @Override
    public String sayHi(String message) {
        return "Hi，your message is :\"" + message + "\" but request error.";
    }
}

【未完待续…..】

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