1、为什么需要Zuul
1.1、Zuul、Ribbon和Eureka相结合,可以实现智能路由和负载均衡的功能,Zuul可以将请求流量按照某种策略分发到集群的多个服务实例上;
1.2、gateway将所有API接口统一聚合,并统一对外暴露,外界系统统一调用gateway提供的接口,外界无需知道微服务直接接口相互的调用关系,为微服务的API接口提供了更高的安全性;
1.3、Gateway服务可以用作身份认证和权限控制,防止非法访问API接口;
1.4、Gateway可以实现监控、日志输出和对请求进行记录;
1.5、Gateway可以实现流量的监控,在高流量的情况下,可以对服务进行降级;
1.6、Gateway将所有接口都统一对外,方便测试。
2、Zuul的工作原理
Zuul是通过Servlet实现的,通过自定义的ZuulServlet对请求进行控制。Zuul的核心是一系列的过滤器,可以在Http请求的发起到相应返回期间执行一系列的过滤器,主要有一下四种过滤器:
a、Pre过滤器,请求路由之前执行的过滤器,主要用做安全验证;
b、Routing过滤器,用于具体路由到微服务的实例,默认使用Http Client进行网络请求;
c、Post过滤器,在请求被路由到微服务后执行的,用作收集统计信息,指标,已经将相应传输到客户端;
d、Error过滤器,在其他过滤器发生错误执行。
由于Zuul的过滤器之间是无法直接通信,所以只能通过RequestContext对象进行共享数据,每个请求都会创建一个RequestContext对象。每个过滤器都有如下特性:
a、Type(类型),过滤器的类型,定义以上4中过滤器的一种;
b、Execution Order(执行顺序),过滤的执行顺序,Order值越小,越优先执行;
c、Criteria(标准),过滤器执行所需的条件;
d、Action(动作),符合Criteria的,则执行具体的Action,具体的逻辑代码实现。
3、源码实战
3.1、建立Zuul服务
新建一个eureka-zuul-client的工程,添加相关依赖,Pom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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.hzlitai</groupId>
<artifactId>eureka-memo</artifactId>
<version>1.1-SNAPSHOT</version>
</parent>
<groupId>com.hzlitai</groupId>
<artifactId>eureka-zuul-client</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>eureka-zuul-client</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-zuul</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
程序的启动类添加相关注解,代码如下:
package com.hzlitai.eurekazuulclient;
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;
@EnableEurekaClient
@EnableZuulProxy
@SpringBootApplication
public class EurekaZuulClientApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaZuulClientApplication.class, args);
}
}
在application.yml配置中增加如下代码:
server:
port: 5000
spring:
application:
name: service-zuul
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka
zuul:
prefix: /v1
routes:
hiapi:
path: /hiapi/**
serviceId: eureka-client
ribbonapi:
path: /rebbonapi/**
serviceId: eureka-ribbon-client
feignapi:
path: /feignapi/**
serviceId: eureka-feign-client
服务端口为:5000,服务实例名:service-zuul,注册到服务中心:serviceUrl,统一版本:prefix,路由配置:routes。
依次启动各个服务后,访问:http://localhost:5000/ribbonapi/sayHi?name=zhuheliang,浏览器会交替出现访问不同端口的结果。可见Zuul在路由转发实现了负载均衡。
3.2、在Zuul上配置熔断器Hystrix
在Zuul实现熔断功能需要实现FallbackProvider接口,实现两个方法:getRoute()和fallbackResponse(),源码如下:
package com.hzlitai.eurekazuulclient.provider;
import com.netflix.hystrix.exception.HystrixTimeoutException;
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;
@Component
public class ZuulFallbackProvider implements FallbackProvider {
@Override
public String getRoute() {
//api服务id(eureka-client),如果需要所有调用都支持回退,则return "*"或 return null
return "*";
}
@Override
public ClientHttpResponse fallbackResponse(String route, Throwable cause) {
if (cause instanceof HystrixTimeoutException) {
return response(HttpStatus.GATEWAY_TIMEOUT);
} else {
return response(HttpStatus.INTERNAL_SERVER_ERROR);
}
}
private ClientHttpResponse response(final HttpStatus status) {
return new ClientHttpResponse() {
@Override
public HttpStatus getStatusCode() throws IOException {
//return status;
return HttpStatus.BAD_REQUEST;
}
@Override
public int getRawStatusCode() throws IOException {
//return status.value();
return HttpStatus.BAD_REQUEST.value();
}
@Override
public String getStatusText() throws IOException {
//return status.getReasonPhrase();
//return HttpStatus.BAD_REQUEST.name();
return HttpStatus.BAD_REQUEST.getReasonPhrase();
}
@Override
public void close() {
}
@Override
public InputStream getBody() throws IOException {
return new ByteArrayInputStream(("fallback:"+ZuulFallbackProvider.this.getRoute()).getBytes());
}
@Override
public HttpHeaders getHeaders() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
return headers;
}
};
}
}
3.3、在Zuul中自定义过滤器
Zuul自定义过滤器只需继承ZuulFilter类,实现ZuulFilter里的抽象方法,有filterType()和filterOrder(),还有IZuulFilter的shouldFilter()和Object run(),示例代码如下:
package com.hzlitai.eurekazuulclient.filter;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;
import org.springframework.stereotype.Component;
import javax.servlet.http.HttpServletRequest;
import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PRE_TYPE;
@Component
public class MyFilter extends ZuulFilter {
@Override
public String filterType() {
return PRE_TYPE;
}
@Override
public int filterOrder() {
return 0;
}
@Override
public boolean shouldFilter() {
return true;
}
@Override
public Object run() throws ZuulException {
RequestContext ctx = RequestContext.getCurrentContext();
HttpServletRequest request = ctx.getRequest();
Object accessToken = request.getParameter("accessToken");
if(accessToken == null){
ctx.setSendZuulResponse(false);
ctx.setResponseStatusCode(401);
try{
ctx.getResponse().getWriter().write("token is empty");
}catch (Exception e){
e.printStackTrace();
}
}
return null;
}
}