使用路由网关统一访问接口

概述

在微服务架构中，需要几个基础的服务治理组件，包括服务注册与发现、服务消费、负载均衡、熔断器、智能路由、配置管理等，由这几个基础组件相互协作，共同组建了一个简单的微服务系统。一个简单的微服务系统如下图：

在 Spring Cloud 微服务系统中，一种常见的负载均衡方式是，客户端的请求首先经过负载均衡（Zuul、Ngnix），再到达服务网关（Zuul 集群），然后再到具体的服。服务统一注册到高可用的服务注册中心集群，服务的所有的配置文件由配置服务管理，配置服务的配置文件放在 GIT 仓库，方便开发人员随时改配置。

#Zuul 简介

Zuul 的主要功能是路由转发和过滤器。路由功能是微服务的一部分，比如 /api/user 转发到到 User 服务，/api/shop 转发到到 Shop 服务。Zuul 默认和 Ribbon 结合实现了负载均衡的功能。

#创建路由网关

pom.xml 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>com.snake</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-zuul</artifactId>
    <packaging>jar</packaging>

    <name>hello-spring-cloud-zuul</name>
    <url>http://www.snake.com</url>
    <inceptionYear>2018-Now</inceptionYear>

    <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-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-netflix-zuul</artifactId>
        </dependency>
        <!-- Spring Cloud End -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.snake.hello.spring.cloud.zuul.ZuulApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

主要是增加了 Zuul 的依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
</dependency>

#Application

增加 @EnableZuulProxy 注解开启 Zuul 功能

package com.snake.hello.spring.cloud.zuul;

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

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

#application.yml

• 设置端口号为：8769
• 增加 Zuul 配置

spring:
  application:
    name: hello-spring-cloud-zuul

server:
  port: 8769

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

zuul:
  routes:
    api-a:
      path: /api/a/**
      serviceId: hello-spring-cloud-web-admin-ribbon
    api-b:
      path: /api/b/**
      serviceId: hello-spring-cloud-web-admin-feign

路由说明：

• 以 /api/a 开头的请求都转发给 hello-spring-cloud-web-admin-ribbon 服务
• 以 /api/b 开头的请求都转发给 hello-spring-cloud-web-admin-feign 服务

#测试访问

依次运行 EurekaApplication、ServiceAdminApplication、WebAdminRibbonApplication、WebAdminFeignApplication、ZuulApplication

打开浏览器访问：http://localhost:8769/api/a/hi?message=HelloZuul 浏览器显示

Hi，your message is :"HelloZuul" i am from port：8763

打开浏览器访问：http://localhost:8769/api/b/hi?message=HelloZuul 浏览器显示

Hi，your message is :"HelloZuul" i am from port：8763

至此说明 Zuul 的路由功能配置成功

#配置网关路由失败时的回调

package com.snake.hello.spring.cloud.zuul.fallback;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
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;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;

/**
 * 路由 hello-spring-cloud-web-admin-feign 失败时的回调
 * <p>Title: WebAdminFeignFallbackProvider</p>
 * <p>Description: </p>
 *
 * @author snake
 * @version 1.0.0
 * @date 2018/7/27 6:55
 */
@Component
public class WebAdminFeignFallbackProvider implements FallbackProvider {

    @Override
    public String getRoute() {
        // ServiceId，如果需要所有调用都支持回退，则 return "*" 或 return null
        return "hello-spring-cloud-web-admin-feign";
    }

    /**
     * 如果请求服务失败，则返回指定的信息给调用者
     * @param route
     * @param cause
     * @return
     */
    @Override
    public ClientHttpResponse fallbackResponse(String route, Throwable cause) {
        return new ClientHttpResponse() {
            /**
             * 网关向 api 服务请求失败了，但是消费者客户端向网关发起的请求是成功的，
             * 不应该把 api 的 404,500 等问题抛给客户端
             * 网关和 api 服务集群对于客户端来说是黑盒
             * @return
             * @throws IOException
             */
            @Override
            public HttpStatus getStatusCode() throws IOException {
                return HttpStatus.OK;
            }

            @Override
            public int getRawStatusCode() throws IOException {
                return HttpStatus.OK.value();
            }

            @Override
            public String getStatusText() throws IOException {
                return HttpStatus.OK.getReasonPhrase();
            }

            @Override
            public void close() {

            }

            @Override
            public InputStream getBody() throws IOException {
                ObjectMapper objectMapper = new ObjectMapper();
                Map<String, Object> map = new HashMap<>();
                map.put("status", 200);
                map.put("message", "无法连接，请检查您的网络");
                return new ByteArrayInputStream(objectMapper.writeValueAsString(map).getBytes("UTF-8"));
            }

            @Override
            public HttpHeaders getHeaders() {
                HttpHeaders headers = new HttpHeaders();
                // 和 getBody 中的内容编码一致
                headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
                return headers;
            }
        };
    }
}