微服务：Eureka+Zuul+Ribbon+Feign+Hystrix构建微服务架构

摘自官方说明：

Spring Cloud Netflix provides Netflix OSS integrations for Spring Boot apps through autoconfiguration and binding to the Spring Environment and other Spring programming model idioms. With a few simple annotations you can quickly enable and configure the common patterns inside your application and build large distributed systems with battle-tested Netflix components. The patterns provided include Service Discovery (Eureka), Circuit Breaker (Hystrix), Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon)..

通过上述可以了解到：

Eureka：服务发现 
Hystrix：断路器 
Zuul：智能路由 
Ribbon：客户端负载均衡

先图话后 

Eureka：实际上在整个过程中维护者每个服务的生命周期。每一个服务都要被注册到Eureka服务器上，这里被注册到Eureka的服务又称为Client。Eureka通过心跳来确定服务是否正常。Eureka只做请求转发。同时Eureka是支持集群的呦！！！ 
Zuul：类似于网关，反向代理。为外部请求提供统一入口。 
Ribbon/Feign：可以理解为调用服务的客户端。 
Hystrix：断路器，服务调用通常是深层的，一个底层服务通常为多个上层服务提供服务，那么如果底层服务失败则会造成大面积失败，Hystrix就是就调用失败后触发定义好的处理方法，从而更友好的解决出错。也是微服务的容错机制。

多说不如看代码

下面我们将搭建一个单Eureka服务器的案例，我们将会注册两个微服务，并配置Zuul。 
目标： 
1.模拟外部请求，访问暴漏端口（Eureka监听端口）访问其中一个内部服务。 
2.演示服务间如何通过Feign进行调用。 
综述： 
我们要写的包括： 
一个Eureka服务器 
两个微服务

抽取出公共的POM部分，让我们专注重点

<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>4.0.0modelVersion>
    <groupId>com.xbz.eureka.demogroupId>
    <artifactId>demo-eureka-serverartifactId>
    <version>0.0.1-SNAPSHOTversion>

    <properties>
        <java.version>1.7java.version>
        <file.encoding>UTF-8file.encoding>
    properties>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloudgroupId>
                <artifactId>spring-cloud-netflixartifactId>
                <version>1.2.2.RELEASEversion>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>
    <dependencies>
        
    dependencies>
<build>
        <plugins>
            <plugin>  
                <artifactId>maven-compiler-pluginartifactId>  
                <version>2.3.2version>  
                <configuration>  
                    <source>${java.version}source>  
                    <target>${java.version}target>  
                    <encoding>${file.encoding}encoding>  
                configuration>  
            plugin> 
        plugins>
    build>

    <repositories>
        <repository>
            <id>spring-snapshotsid>
            <name>Spring Snapshotsname>
            <url>https://repo.spring.io/libs-snapshoturl>
            <snapshots>
                <enabled>trueenabled>
            snapshots>
        repository>
    repositories>
project>

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---

Eureka单例服务器（即不将自身作为一个Client）  
我们只需要三个步骤就可以启动服务器 
1.POM引入

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-eurekaartifactId>
dependency>
<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-zuulartifactId>
dependency>
<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-eureka-serverartifactId>
dependency>

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2.搞个Main启动类 
@EnableEurekaServer 
@EnableZuulProxy

package com.xbz.eureka.demo.server;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@SpringBootApplication
@EnableEurekaServer
@EnableZuulProxy
public class EnurekaServer {
    public static void main(String[] args) {
        new SpringApplicationBuilder(EnurekaServer.class).web(true).run(args);
    }
}

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3.重点：application.yml

#单例模式启动Eureka Server
server:
  port: 8761 #启动端口
eureka:
  client:
    registerWithEureka: false #false:不作为一个客户端注册到注册中心   
    fetchRegistry: false #为true时，可以启动，但报异常：Cannot execute request on any known server
zuul:
  prefix: /techouse #为zuul设置一个公共的前缀
  #ignoredServices: '*'
  routes:
    cloud-client: #随便定义，当不存在serviceId时，默认该值为serviceId（就是注册服务的名称，属性spring.application.name）
      path: /usersystem/** #匹配/techouse/usersystem/** 均路由到cloud-client
      serviceId: cloud-client #指定路由到的serviceId
ribbon:
  eureka:
    enabled: false #配置zuul路由时用将此属性设置为false

cloud-client:
  ribbon:
    listOfServers: 127.0.0.1:8800 #为cloud-client服务指定一组服务地址，应该是用于负载均衡

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---

两个微服务  
服务cluod-client  
客户端pom

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-eurekaartifactId>
dependency>
<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-hystrixartifactId>
dependency>

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    这个服务我们在上面的application.yml中配置了，等下我们就可以用Eureka服务器地址访问此服务。 
该服务包含一个HellController，和ServerApplication(启动类) 
HelloController.java

package com.xbz.eureka.demo.client.controller;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

@RestController
public class HelloController {
    @RequestMapping("/hello/{fallback}")
    @HystrixCommand(fallbackMethod="helloFallbackMethod")/*调用方式失败后调用helloFallbackMethod*/
    public String hello(@PathVariable("fallback") String fallback){
        if("1".equals(fallback)){
            throw new RuntimeException("...");
        }
        return "hello";
    }

    public String helloFallbackMethod(String fallback){
        return "fallback 参数值为:"+fallback;
    }
}

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ServerApplication.java 
@EnableEurekaClient，确保该应用注册到Eureka服务器 
@EnableHystrix 断路器生效

package com.xbz.eureka.demo.client;

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

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

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重要的application.xml

server:
  port: 8800
spring:
  application:
    name: cloud-client #为你的应用起个名字，该名字将注册到eureka注册中心
eureka:
  instance:
    statusPageUrlPath: ${management.context-path}/info
    healthCheckUrlPath: ${management.context-path}/health
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/ #去哪里注册，eureka服务地址

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服务cluod-client-consumer 
这个服务要调用cloud-client服务中的/hello/{fallback}方法 
使用@Feign(“服务名称”),接口中随便定义方法，然后@RequestMapping(“/hello/{fallback}”)即可，内部调用就是如此简单。 
涉及HelloService（演示如何使用@Feign）调用服务。HelloController演示调用服务的输出结果，以及ConsumerApplication启动类。 
HelloService.java

package com.xbz.eureka.demo.consumer;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient("cloud-client")
public interface HelloService {
    @RequestMapping("/hello/{fallback}")
    public String hello(@PathVariable("fallback") String fallback);
}

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HelloController.java

package com.xbz.eureka.demo.consumer;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
    @Autowired
    private HelloService helloServcie;
    @RequestMapping("/test/{fallback}")
    public String hello(@PathVariable("fallback") String fallback){
        String res=helloServcie.hello(fallback);
        return "调用服务结果为"+res;
    }
}

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启动类ConsumerApplication.java 
@EnableEurekaClient注册到Eureka 
@EnableFeignClients 内部使用Feign调用服务 
@EnableZuulProxy 必须要有这个注解

package com.xbz.eureka.demo.consumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

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

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重要application.xml

server:
 port: 8080
spring:
  application:
   name: cloud-consumer #为你的应用起个名字，该名字将注册到eureka注册中心
eureka:
  instance:
    statusPageUrlPath: ${management.context-path}/info
    healthCheckUrlPath: ${management.context-path}/health
  client:
    serviceUrl:
      defaultZone: http://hadoopMaster:8761/eureka/ #去哪里注册，eureka服务地址

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---

至此，我们的服务就搭建起来了！！！ 
按顺序启动三个类： 
EurekaServer 
ServiceApplication 
ConsumerApplication 
正常情况下，访问 http://127.0.0.1:8761 将看到如下界面 

图中展示了我们启动的两个服务。 
1.访问 http://127.0.0.1:8080/test/1 测试服务内部调用，且失败会调用fallback方法返回值。 
2.访问 http://127.0.0.1:8080/test/2 测试服务内部调用，则正常调用cloud-client的服务。 
3.我们可以使用统一入口，调用cloud-client服务： 
访问的url： http://127.0.0.1:8761/techouse/usersystem/hello/2  
以上便是一个简单的微服务搭建喽！！！