这是 Zuul 1.x: 同步阻塞网关的实现
后来，Zuul 2.x(简称基于Gateway): 基于Gateway异步非阻塞网关的实现。因为Netflix后期不再维护Zuul 2.x而是采用Gateway，并且Gateway原理和Zuul 2.x相同，所以基于Zuul 2.x简称基于Gateway

main

2 services:

  1. one springboot application providing a service/URL;
  2. another application, i.e. Zuul gateway, configured to provide another service which is based on 1st service.

为什么用网关zuul? 因为在微服务架构模式下，后端服务的实例数一般是动态的，比如可能加入一个新的服务，这个可能就有一个影射关系, i.e. 新加入的服务跟之前的服务有一定的联系，而对客户端而言很难发现动态改变的服务实例的访问地址信息。这个时候就会基于zuul做一个跟nginx类似的一个反向代理，对应某一个path，把它转给某一个server ID. 同时我们在zuul上面也用了zuulset对授权服务，健全服务的集成。

zuul 常见的有这两种配置的方式，一个是这种直接对 path 的转发，比如某一个网站直接转过去；另外一个是对 server ID，比如所有注册中心的服务都可以通过它的 server ID 做一个对应的请求的转发。

下面的zuul网关的用法是直接对path的转发。

附: 我发现服务的写法，都是: add dependency > resource下的application.properties > java下的类

1st service

(normal springboot project)

pom.xml:

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

application.properties:

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spring.application.home=student
server.port=8090
...

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@RestController
@SpringBootApplication
public class SpringBootZuulGatewayProxyStudentServiceApplication {

	@RequestMapping(value = "/echoStudentName/{name}")
	public String echoStudentName(@PathVariable(name = "name") String name) {
		return "hello" + name;
	}

	@RequestMapping(value = "/getStudentDetails/{name}")
	public Student getStudentDetails(@PathVariable(name = "name") String name) {
		return new Student(name, "sh", "www");
	}

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

access via:

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http://localhost:8090/echoStudentName/lei
http://localhost:8090/getStudentDetails/lei

1st service keeps running. Next, make a Zuul gateway.

2nd service

(in a 2nd project)

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<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-zuul</artifactId>
</dependency>
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@SpringBootApplication
@EnableZuulProxy  // this annotation
public class SpringBootZuulgatewayproxyApplication {

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

	@Bean
	public PreFilter preFilter() {
		return new PreFilter();
	}

	@Bean
	public PostFilter postFilter() {
		return new PostFilter();
	}

	@Bean
	public ErrorFilter errorFilter() {
		return new ErrorFilter();
	}

	@Bean
	public RouteFilter routeFilter() {
		return new RouteFilter();
	}

}
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# Zuul routes. For /student path here, we are routing to localhost:8090 with extra path after that
zuul.routes.student.url=http://localhost:8090
# Ribbon is auto integrated with Zuul and for this exercise we are not using that
ribbon.eureka.enabled=false
# Will start gateway server @8080
server.port=8080
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http://localhost:8080/student/echoStudentName/lei
http://localhost:8080/student/getStudentDetails/lei

服务运行在端口8090，网关开启运行在端口8080，通过网关实现了服务的转发.

基于 Gateway实现API网关: 可以基于java代码或者基于配置实现