网关在微服务里的角色
在微服务架构体系里,网关是非常重要的一个环节,它主要实现了一些功能的统一处理,包括了:
 * 统一授权 
 * 统一异常处理 
 * 路由导向 
 * 跨域处理 
 * 限流 
实践一下
1 添加依赖
dependencies { 
implementation('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client') 
implementation('org.springframework.cloud:spring-cloud-starter-netflix-zuul') 
testImplementation('org.springframework.boot:spring-boot-starter-test') 
implementation('com.marcosbarbero.cloud:spring-cloud-zuul-ratelimit:1.3.2.RELEASE') 
} 
2 添加yml
server: port: 8300 spring: application: name: microservice-gateway-zuul 
eureka: client: register-with-eureka: true fetch-registry: true service-url: 
defaultZone: http://localhost:6761/eureka instance: ip-address: true zuul: 
routes: users: path: /lind/** #以lind开头的路径被重定向到lind服务 serviceId: lind 
add-host-header: true #显示真实的http头 retryable: false #关闭Hystrix的重试功能 ratelimit: 
enabled: true # repository: REDIS behind-proxy: true policies: users: limit: 5 
#限流,每分钟请求5次 refresh-interval: 60 type: - user - origin - url # 
url类型的限流就是通过请求路径区分 # origin是通过客户端IP地址区分 # user是通过授权用户进行区分,也包括匿名用户 
3 添加实现代码
 http拦截器,获取用户ID,为子服务进行传递
public class PreRequestLogFilter extends ZuulFilter { private static final 
Logger logger = LoggerFactory.getLogger(PreRequestLogFilter.class); private 
final RateLimiter rateLimiter = RateLimiter.create(1000.0); @Override public 
Object run() { try { RequestContext currentContext = 
RequestContext.getCurrentContext(); HttpServletResponse response = 
currentContext.getResponse(); HttpServletRequest reqeust = 
currentContext.getRequest(); 
currentContext.addZuulRequestHeader("userId","123");//向子系统http头写数据 
currentContext.addZuulRequestHeader("userName","test"); 
PreRequestLogFilter.logger.info( String.format("send %s request to %s", 
reqeust.getMethod(), reqeust.getRequestURL().toString())); if 
(!rateLimiter.tryAcquire()) { HttpStatus httpStatus = 
HttpStatus.TOO_MANY_REQUESTS; 
response.setContentType(MediaType.TEXT_PLAIN_VALUE); 
response.setStatus(httpStatus.value()); 
response.getWriter().append(httpStatus.getReasonPhrase()); 
currentContext.setSendZuulResponse(false); throw new ZuulException( 
httpStatus.getReasonPhrase(), httpStatus.value(), httpStatus.getReasonPhrase() 
); } } catch (java.lang.Exception e) { 
ReflectionUtils.rethrowRuntimeException(e); } return null; } @Override public 
boolean shouldFilter() { // 判断是否需要过滤 return true; } @Override public String 
filterType() { return FilterConstants.PRE_TYPE; } @Override public int 
filterOrder() { return Ordered.HIGHEST_PRECEDENCE; } } 
在主程中注入这个过滤器
 @Bean public PreRequestLogFilter preRequestLogFilter() { return new 
PreRequestLogFilter(); } 
4 使用它
 在URL上通过localhost:8300/users/home 
将进行lind服务里的home控制器下,并在http头上写入了userid和username这个键值对!
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