续 Eureka+Hystrix+Zuul（Zuul API网关）

概述：

服务的合并，转发，验证，异构协议。将上百个请求融为一个发送到后台，返回大的JSON返回处理；

作用：这减少了客户端与应用程序间的交互次数，还简化了客户端代码。

Zuul可以通过加载动态过滤机制，从而实现以下各项功能：

l 验证与安全保障: 识别面向各类资源的验证要求并拒绝那些与要求不符的请求。

l 审查与监控: 在边缘位置追踪有意义数据及统计结果，从而为我们带来准确的生产状态结论。

l 动态路由: 以动态方式根据需要将请求路由至不同后端集群处。

l 压力测试: 逐渐增加指向集群的负载流量，从而计算性能水平。

l 负载分配: 为每一种负载类型分配对应容量，并弃用超出限定值的请求。

l 静态响应处理: 在边缘位置直接建立部分响应，从而避免其流入内部集群。

l 多区域弹性: 跨越AWS区域进行请求路由，旨在实现ELB使用多样化并保证边缘位置与使用者尽可能接近。

除此之外，Netflix公司还利用Zuul的功能通过金丝雀版本实现精确路由与压力测试。

具体实现：Eureka整合Zuul，并实现断路器

1.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>client.Zuul</groupId>
    <artifactId>client-Zuul</artifactId>
    <version>0.0.1-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.cloud</groupId>
            <artifactId>spring-cloud-starter-zuul</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <!-- Hystrix，Feign是基于Hystrix的 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</artifactId>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

</project>

2.启动项 ZuulRunApp

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
 
@SpringBootApplication
@EnableZuulProxy
public class ZuulRunApp {
 
    public static void main(String[] args) {
        SpringApplication.run(ZuulRunApp.class, args);
    }
 
}

　　application.yml

server:
  port: 8050
spring:
  application:
    name: client-Zuul
eureka:
  client:
    serviceUrl:
      defaultZone: http://user:password123@localhost:8761/eureka
zuul:
  routes:
    app-a:
      path: /user/**
      serviceId: consumer-Hystrix

ZuulFallBack.java

package cn.hz.fallback;
 
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
 
import org.springframework.cloud.netflix.zuul.filters.route.ZuulFallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;
 
@Component
public class ZuulFallBack implements ZuulFallbackProvider{
 
    @Override
    public String getRoute() {
        //为了通用，写了个*
        return "*";
    }
 
    @Override
    public ClientHttpResponse fallbackResponse() {
        return new ClientHttpResponse() {
             
            @Override
            public HttpHeaders getHeaders() {
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
                return headers;
            }
             
            @Override
            public InputStream getBody() throws IOException {
                String msg = "This is responseContext!";
                return new ByteArrayInputStream(msg.getBytes());
            }
             
            @Override
            public String getStatusText() throws IOException {
                return HttpStatus.BAD_REQUEST.getReasonPhrase();
            }
             
            @Override
            public HttpStatus getStatusCode() throws IOException {
                return HttpStatus.BAD_REQUEST;
            }
             
            @Override
            public int getRawStatusCode() throws IOException {
                return HttpStatus.BAD_REQUEST.value();
            }
             
            @Override
            public void close() {
                 
            }
        };
    }
 
}