系列文章：
微服务架构：网关概念与 zuul
微服务网关：Spring Cloud Gateway —— Zuul
微服务网关：Spring Cloud Config- 配置中心
微服务网关方案：Kong & Nacos
Nacos 实践
微服务网关：Nacos 源码实践（二）
微服务注册中心：Consul——概念与基础操作
一 简介
微服务注册中心：Consul——概念与基础操作介绍了 consul 的安装和基本操作，本篇开始在 consul 上进行服务注册与发现，语言使用 Java，框架使用 Spring Boot 整合 Consul。
二 Spring Boot 整合 Consul
通常 demo 比较好找，导入后观察需要引入哪些依赖，然后启动。最多微调版本和配置问题即可。
2.1 网上 demo
打脸来的如此迅速，百度上搜了一堆，最后发现都是官方文档的翻译，版本不清，代码不全，尝试几个未果。再次感叹现在很多文章的质量。
2.2 官方文档
不得已还是先尝试查看官方文档，Spring Cloud Consul是基于 3.0.2 版本，给出的集成 demo。不过很遗憾，官方给出的 sample 地址，访问一直是 404 状态。
上面 Consul Sample 的查看结果：
2.3 spring-cloud 的 github
考虑下一种渠道，寻找官方github。官方的 pom.xml 配置建议如下：
<project><parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>{spring-boot-version}</version> <relativePath/> <!-- lookup parent from repository --> </parent>
<dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-consul-discovery</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>
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事实上，springboot 的版本选择过程中也遇到不少问题，几个典型的错误如下（为了节省空间，只截取了关键错误信息）：
2.3.1 启动报错信息 1
Description:
An attempt was made to call a method that does not exist. The attempt was made from the following location:
org.springframework.cloud.client.discovery.health.DiscoveryCompositeHealthIndicator.<init>(DiscoveryCompositeHealthIndicator.java:41)
The following method did not exist:
org.springframework.boot.actuate.health.CompositeHealthIndicator.<init>(Lorg/springframework/boot/actuate/health/HealthAggregator;)V
The method's class, org.springframework.boot.actuate.health.CompositeHealthIndicator, is available from the following locations:
jar:file:/Users/lijingyong/.m2/repository/org/springframework/boot/spring-boot-actuator/2.2.6.RELEASE/spring-boot-actuator-2.2.6.RELEASE.jar!/org/springframework/boot/actuate/health/CompositeHealthIndicator.class
It was loaded from the following location:
file:/Users/lijingyong/.m2/repository/org/springframework/boot/spring-boot-actuator/2.2.6.RELEASE/spring-boot-actuator-2.2.6.RELEASE.jar
Action:
Correct the classpath of your application so that it contains a single, compatible version of org.springframework.boot.actuate.health.CompositeHealthIndicator
Process finished with exit code 1
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2.3.2 报错 2
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.cloud.consul.serviceregistry.ConsulAutoRegistration]: Factory method 'consulRegistration' threw exception; nested exception is java.lang.IllegalArgumentException: Consul service ids must not be empty, must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen: null at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE] at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE] ... 96 common frames omittedCaused by: java.lang.IllegalArgumentException: Consul service ids must not be empty, must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen: null at org.springframework.cloud.consul.serviceregistry.ConsulAutoRegistration.normalizeForDns(ConsulAutoRegistration.java:178) ~[spring-cloud-consul-discovery-2.2.1.RELEASE.jar:2.2.1.RELEASE]
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2.4 一个可用 demo
根据官方说明，并参考另一个 demo：https://github.com/RobbieXie/springboot-consul 后，整理如下，不过是使用的较旧版本 springboot，可以根据需要更新到适合的版本信息。
关键配置和代码：
2.4.1 pom.xml
<?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>org.example</groupId> <artifactId>springboot-consul</artifactId> <description>Spring Boot整合consul示例</description> <version>1.0-SNAPSHOT</version>
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.9.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> </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>com.orbitz.consul</groupId> <artifactId>consul-client</artifactId> <version>1.0.0</version> </dependency> <dependency> <groupId>com.ecwid.consul</groupId> <artifactId>consul-api</artifactId> <version>1.3.0</version> </dependency> </dependencies>
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
<repositories> <repository> <snapshots> <enabled>false</enabled> </snapshots> <id>central</id> <name>bintray</name> <url>http://jcenter.bintray.com</url> </repository> </repositories></project>
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2.4.2 应用启动类 SpringBootConsulApplication
package com.flamingskys.learn.springboot.consul;
import com.flamingskys.learn.springboot.consul.service.ConsulService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Value;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.EnableAutoConfiguration;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.context.annotation.Bean;
import javax.annotation.PreDestroy;
@SpringBootApplication@EnableAutoConfigurationpublic class SpringBootConsulApplication {
@Value("${consul.instanceId}") private String instanceId;
@Bean public String getInstanceId(){ return instanceId; }
@Autowired private ConsulService consulService;
public static void main(String[] args) { SpringApplication.run(SpringBootConsulApplication.class, args); }
@PreDestroy public void beforeExit(){ System.out.println("-----------------------------BEFORE EXIT--------------------------------"); consulService.deregisterService(instanceId); }}
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2.4.3 资源配置 application.properties
spring.application.name=first-consul-client
consul.host=127.0.0.1consul.port=8500consul.instanceId=${spring.application.name}:${spring.application.instanceid:${random.value}}
spring.cloud.consul.discovery.heartbeat.enabled=true
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应用启动后，查看 console 上注册的服务列表，first-consul-client 就是我们的服务：
完整代码已上传到了gitee。可关注公众号：程序员架构进阶 随时获取更新。
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