Spring Cloud基础教程（七）：路由网关使用（Zuul）

一、概述

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/client-a/转发到到a服务，/client-b/转发到到b服务。zuul默认和Ribbon结合实现了负载均衡的功能。

二、准备

将服务注册与发现这篇博客中的Eureka-Client-A工程，复制一份，名字修改为Service-Zuul。

三、工程修改

Gradle依赖修改为

dependencies {
	compile('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client')
	compile('org.springframework.cloud:spring-cloud-starter-zuul:1.4.4.RELEASE')
	compile('org.springframework.boot:spring-boot-starter-web')
	testCompile('org.springframework.boot:spring-boot-starter-test')
}

在启动类上添加@EnableZuulProxy注解，开启路由功能。

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 EurekaZuulApplication
{

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

修改application.properties配置文件，将/client-a/开头的请求路由到eureka-client-a服务器

spring.application.name=service-zuul
server.port=10010
eureka.client.serviceUrl.defaultZone=http://localhost:10001/eureka/

zuul.routes.api-a.path: /client-a/**
zuul.routes.api-a.serviceId: eureka-client-a

四、测试

启动之前的Eureka-Server、Eureka-Client-A和当前的Service-Zuul工程，访问http://127.0.0.1:10001/

发现都已经注册到了注册中心，访问http://127.0.0.1:10010/client-a/client，会发现路由到了Eureka-Client-A

五、服务过滤

Zuul不仅有路由的功能，还有服务过滤的功能，做一些拦截验证。

新建MyFilter类

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.servlet.http.HttpServletRequest;

/**
 * Created by wzj on 2018/5/24.
 */
@Component
public class MyFilter extends ZuulFilter
{
    private static Logger log = LoggerFactory.getLogger(MyFilter.class);

    /**
     * to classify a filter by type. Standard types in Zuul are "pre" for pre-routing filtering,
     * "route" for routing to an origin, "post" for post-routing filters, "error" for error handling.
     * We also support a "static" type for static responses see  StaticResponseFilter.
     * Any filterType made be created or added and run by calling FilterProcessor.runFilters(type)
     *
     * @return A String representing that type
     */
    @Override
    public String filterType()
    {
        return "pre";
    }

    /**
     * filterOrder() must also be defined for a filter. Filters may have the same  filterOrder if precedence is not
     * important for a filter. filterOrders do not need to be sequential.
     *
     * @return the int order of a filter
     */
    @Override
    public int filterOrder()
    {
        return 0;
    }

    /**
     * a "true" return from this method means that the run() method should be invoked
     *
     * @return true if the run() method should be invoked. false will not invoke the run() method
     */
    @Override
    public boolean shouldFilter()
    {
        return true;
    }

    /**
     * if shouldFilter() is true, this method will be invoked. this method is the core method of a ZuulFilter
     *
     * @return Some arbitrary artifact may be returned. Current implementation ignores it.
     * @throws ZuulException if an error occurs during execution.
     */
    @Override
    public Object run() throws ZuulException
    {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        log.info(String.format("%s >>> %s", request.getMethod(), request.getRequestURL().toString()));
        Object accessToken = request.getParameter("token");
        if (accessToken == null)
        {
            log.warn("token is empty");
            ctx.setSendZuulResponse(false);
            ctx.setResponseStatusCode(401);
            try
            {
                ctx.getResponse().getWriter().write("token is empty");
            }
            catch (Exception e)
            {
            }

            return null;
        }
        log.info("ok");
        return null;
    }
}

filterType：返回一个字符串代表过滤器的类型，在zuul中定义了四种不同生命周期的过滤器类型，具体如下： 

• pre：路由之前
• routing：路由之时
• post： 路由之后
• error：发送错误调用
• filterOrder：过滤的顺序
• shouldFilter：这里可以写逻辑判断，是否要过滤，本文true,永远过滤。
• run：过滤器的具体逻辑。可用很复杂，包括查sql，nosql去判断该请求到底有没有权限访问。

服务重启，再次访问http://127.0.0.1:10010/client-a/client，界面显示如下

再次输入http://127.0.0.1:10010/client-a/client?token=1001