Spring Cloud学习笔记----消息总线（Spring Cloud Bus)（2018-08-03）

在上一篇的基础上进行完善，
之前的缺陷是：当远程git端的配置文件更改的时候，serviceOne需要重新启动一下，才能读取到改变后的配置文件。
解决方案：采用轻量级的消息代理借助Spring Cloud Bus将分布式的节点链接起来，用于广播配置文件的更改或者服务之间的通讯。

---

我们重新起一个服务，serviceTwo, pom文件如下,加入spring-cloud-starter-bus-amqp依赖

<?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>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>serviceTwo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.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.SR1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bus-amqp</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</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.properties如下

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest

spring.cloud.bus.enabled=true
spring.cloud.bus.trace.enabled=true
management.endpoints.web.exposure.include=bus-refresh

bootstrap.properties如下

spring.application.name=serviceTwo
spring.cloud.config.label=master
spring.cloud.config.profile=dev


eureka.client.serviceUrl.defaultZone=http://localhost:9999/eureka/
spring.cloud.config.discovery.enabled=true
spring.cloud.config.discovery.serviceId=configServerCenter
server.port=7778

修改入口程序如下

package com.example.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@EnableDiscoveryClient
@EnableEurekaClient
@RestController
@RefreshScope
@SpringBootApplication
public class ServiceTwoApplication {

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

    @Value("${valueFromGit}")
    String valueFromGit;

    @RequestMapping("/getValueFromGit")
    public String getValueFromGit(){
        return valueFromGit;
    }

}

至此，对于serviceTwo来说，当远程git库中的serviceTwo-dev.properties发生改变的时候，发送post请求http://localhost:7778/actuator/bus-refresh 即可让serviceTwo重新访问配置服务中心configServerCenter拿去新的配置文件并读取。

发送post请求的时候Content-Type的类型是application/json;charset=UTF-8

至此借助消息总线完成了不用重启serviceTwo也能对配置文件进行更新的功能。