Spring cloud学习之Zuul入门篇

太过爱你忘了你带给我的痛 2022-01-27 05:53 223阅读 0赞

最近需要做一次分享，简单的demo肯定拿不出来，因此打算看看源码弄清楚Zuul的一次转发

准备工作(本文使用的Spring cloud版本是Greenwich:SR1)：

注册中心、zuul网关、具体后端服务

先搭建这几个服务：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 2][]

以上是建一个空maven工程，用做父工程，接下来搭建eureka-server

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 6][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 7][]

若出现jar无法导入的情况，在父工程pom.xml中加入

<modules>
        <module>eureka-server</module>
    </modules>

习惯用yml做配置文件，修改application.properties文件后缀为.yml（可以不修改，不修改就使用properties的key=value形式配置）

# 端口
    server:
      port: 9000
    
    spring:
      application:
        name: eureka-server
    
    # eureka配置
    eureka:
      client:
        fetchRegistry: false
        registerWithEureka: false
        serviceUrl:
          defaultZone: http://localhost:${server.port}/eureka/

在主启动类上加上注解@EnableEurekaServer

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

接下来搭建后端服务

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 8][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 9][]

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在父工程pom.xml加入module

<modules>
            <module>eureka-server</module>
            <module>service-a</module>
        </modules>

修改配置文件、主启动类

# 端口
    server:
      port: 9001
    
    spring:
      application:
        name: service-a
    # eureka
    eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:9000/eureka/

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

提供一个接口供测试用：

@RestController
    public class TestController {
    
        @GetMapping("/hello")
        public void hello() {
            System.out.println("hello spring cloud!");
        }
    
    }

Zuul网关服务器

同样使用Spring initializr创建zuul-demo服务，勾选服务时选择

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 14][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 15][]

修改properties属性文件为yml，同时加入一下配置

# 端口
    server:
      port: 9002
    
    spring:
      application:
        name: zuul-demo
    # eureka
    eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:9000/eureka/
    # zuul配置
    zuul:
      routes:
        rules1:
          serviceId: service-a
          path: /api-a/**

@RestController
    public class TestController {
    
        @GetMapping("/hello")
        public String hello() {
            return "hello spring cloud!";
        }
    
    }

启动这3个工程,用postman、或者浏览器访问http://localhost:9002/api-a/hello

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 16][]

接下来通过看源码来看看一次转发zuul做来哪些事情

先看下zuul配置类ZuulProxyAutoConfiguration

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 17][]

注意红框内等2个过滤器，一个前置过滤器，一个路由过滤器，先重点看看路由过滤器RibbonRoutingFilter，看看这个过滤器的run()方法

@Override
    	public Object run() {
    		RequestContext context = RequestContext.getCurrentContext();
    		this.helper.addIgnoredHeaders();
    		try {
    			RibbonCommandContext commandContext = buildCommandContext(context);
    			ClientHttpResponse response = forward(commandContext);
    			setResponse(response);
    			return response;
    		}
    		catch (ZuulException ex) {
    			throw new ZuulRuntimeException(ex);
    		}
    		catch (Exception ex) {
    			throw new ZuulRuntimeException(ex);
    		}
    	}

run()方法调用来一个forward()方法，再来看看forward()方法

protected ClientHttpResponse forward(RibbonCommandContext context) throws Exception {
    		Map<String, Object> info = this.helper.debug(context.getMethod(),
    				context.getUri(), context.getHeaders(), context.getParams(),
    				context.getRequestEntity());
    
    		RibbonCommand command = this.ribbonCommandFactory.create(context);
    		try {
    			ClientHttpResponse response = command.execute();
    			this.helper.appendDebug(info, response.getRawStatusCode(),
    					response.getHeaders());
    			return response;
    		}
    		catch (HystrixRuntimeException ex) {
    			return handleException(info, ex);
    		}
    
    	}

ribbonCommandFactory.create(context)实际是调用HttpClientRibbonCommandFactory类中的create方法（我是怎么知道的，咳咳。。笨方法，将所有实现类打断点，调用时进入哪个就知道类）。看看此类的create方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 18][]

从字面上理解，FallbackProvider zuulFallbackProvider = getFallbackProvider(context.getServiceId());是获取serviceId下的所有熔断降级处理方法。final RibbonLoadBalancingHttpClient client = this.clientFactory.getClient(serviceId, RibbonLoadBalancingHttpClient.class);是创建一个httpClient用来执行调用服务并获取响应。client.setLoadBalancer(this.clientFactory.getLoadBalancer(serviceId));设置负载均衡。最后创建了一个HttpClientRibbonCommand返回。

证实刚刚猜测-创建一个httpClient，可以看到RibbonLoadBalancingHttpClient继承AbstractLoadBalancingClient

![20190525215034584.png][]

再看看CloseableHttpClient类

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 19][]

接下来看看ClientHttpResponse response = command.execute();具体实现是哪个类的方法。上面已经知道command实际是HttpClientRibbonCommand，来看看command.extcute()

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 20][]

HttpClientRibbonCommand没有execute方法，前面说过httpClient实际是执行调用方法的，直接RibbonLoadBalancingHttpClient查看，果然找到来execute()方法，看看该方法做了什么

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDcwMzkz_size_16_color_FFFFFF_t_70 21][]

封装参数执行转发并获取响应 this.delegate.execute()

上面方法主要做的就是组装请求参数(包括各种超时时间)，然后发起转发请求，最终获取相应结果。

总结：

•Zuul转发一次请求原理

1、zuul的转发是通过RibbonRoutingFilter这个Filter进行操作的。

2、在转发之前，zuul利用Hystrix将此次转发请求包装成一个HystrixCommand，这样使得zuul具有了降级(Fallback)的功能

3、在HystrixCommand内部zuul再次将请求包装成一个Observable，(有关RxJava的知识请参照其官方文档)。在观察者模式下调用httpClient执行

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