zuul介绍

Zuul是Netflix的基于JVM的路由器和服务器端负载均衡器,提供了API网关的功能。

API网关是一个服务器，也可以是进入系统的唯一节点。这与面向对象设计的门面模式很像。
API网关封装内部系统的架构。并且提供API给各个客户端，它还可能具备授权，监控，负载均衡，缓存，请求分片，管理，静态响应处理等功能。

API网关具有有点，也具有缺点

优点

API网关的最大有点就是分装了应用程序内部结构。客户端需要和网关交互，不必和特定的服务交互。API网关为每一类客户端提供了特定的API。减少了客户端和应用程序的交互次数，简化了客户端的代码。

缺点

它增加了部署，维护的工作量。API网关变成了瓶颈，API网关的存在，需要走网络，也会有一点的性能损耗。

入门实例

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>com.example</groupId>
    <artifactId>spring-cloud-zuul</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-cloud-zuul</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.7.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>Camden.SR7</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zuul</artifactId>
        </dependency>
        <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>
    </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.yml

server:
  port: 9004
spring:
  application:
    name: spring-cloud-zuul
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka
  instance:
    prefer-ip-address: true

SpringCloudZuulApplication.java

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
@EnableZuulProxy
@SpringBootApplication
public class SpringCloudZuulApplication {

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

验证

浏览器打开http://192.168.88.101:9004/spring-cloud-provider/user/get?id=1

spring-cloud-provider是微服务的application.name

反复刷新页面，浏览器会交替显示下面的内容:

{"id":"1","userName":"xiaoming1","age":30,"birthday":null}
{"id":"1","userName":"xiaoming","age":30,"birthday":null}