Zuul实现Groovy加载动态Filter

一、什么是动态Filter

Zuul提供了一个能够对过滤器进行动态的加载、编译、运行的框架。这些过滤器是由Groovy写成，被放在Zuul Server上的特定目录下面。Zuul会按期轮询这些目录，修改过的过滤器会动态的加载到Zuul Server中。这样如果要对过滤器有改动，就不用进行网关的重新发布了，只需要把过滤器上传到指定目录即可

下面我们就基于spring-cloud-starter-zuul（SpringCloud版本为Edgware.SR3）进行扩展，实现动态加载Filter的功能

二、Zuul动态Filter实现

1）、添加groovy依赖

        <dependency><groupId>org.codehaus.groovy</groupId><artifactId>groovy-all</artifactId><version>2.4.12</version></dependency>

2）、加载Groovy脚本

平常开发中有时需要实现在项目启动后执行的功能，SpringBoot提供的一种简单的实现方案就是添加一个Bean并实现CommandLineRunner接口，实现功能的代码放在实现的run方法中

多个CommandLineRunner接口的实现类时，通过@Order注解指定执行顺序

@Component
@Order(value = 1)
public class GroovyLoadLineRunner implements CommandLineRunner {@Overridepublic void run(String... strings) throws Exception {FilterLoader.getInstance().setCompiler(new GroovyCompiler());//读取配置,获取脚本根目录String scriptRoot = System.getProperty("zuul.filter.root", "groovy/filters");//获取刷新间隔String refreshInterval = System.getProperty("zuul.filter.refreshInterval", "5");if (scriptRoot.length() > 0) {scriptRoot = scriptRoot + File.separator;}FilterFileManager.setFilenameFilter(new GroovyFileFilter());FilterFileManager.init(Integer.parseInt(refreshInterval), scriptRoot + "pre",scriptRoot + "route", scriptRoot + "post");}
}

3）、编写Groovy脚本

import com.netflix.zuul.ZuulFilter
import com.netflix.zuul.context.RequestContext
import org.apache.catalina.servlet4preview.http.HttpServletRequest
import org.slf4j.Logger
import org.slf4j.LoggerFactory
import org.springframework.cloud.netflix.zuul.filters.support.FilterConstantsclass GroovyFilter extends ZuulFilter {private static final Logger LOGGER = LoggerFactory.getLogger(GroovyFilter.class)@OverrideString filterType() {return FilterConstants.PRE_TYPE}//过滤器优先级@Overrideint filterOrder() {return 5}@Overrideboolean shouldFilter() {return true}@OverrideObject run() {HttpServletRequest request = (HttpServletRequest) RequestContext.getCurrentContext().getRequest()Enumeration<String> headerNames = request.getHeaderNames()while (headerNames.hasMoreElements()) {String name = (String) headerNames.nextElement()String value = request.getHeader(name)LOGGER.info("header: " + name + ":" + value)}LOGGER.info("This is Groovy Filter")return null}}

现在idea目录中创建存放过滤器的文件夹

启动参数中指定加载网关的目录

-Dzuul.filter.root=/Users/hanxiantao/Desktop/学习笔记/Zuul深入学习/zuul_lab/lab05/zuul_gateway/groovy/filters

先不把Groovy脚本放到目录下，请求网关，并没有GroovyFilter中打印的日志

再把Groovy脚本放到目录下，请求网关，打印日志如下：

三、Zuul动态加载Filter源码解析

下面我们来看下Zuul是如何实现动态加载Filter的，GroovyLoadLineRunner中我们最后调用了FilterFileManager的init()方法

public class FilterFileManager {/*** Initialized the GroovyFileManager.** @param pollingIntervalSeconds the polling interval in Seconds* @param directories            Any number of paths to directories to be polled may be specified* @throws IOException* @throws IllegalAccessException* @throws InstantiationException*/public static void init(int pollingIntervalSeconds, String... directories) throws Exception, IllegalAccessException, InstantiationException {if (INSTANCE == null) INSTANCE = new FilterFileManager();INSTANCE.aDirectories = directories;INSTANCE.pollingIntervalSeconds = pollingIntervalSeconds;INSTANCE.manageFiles();INSTANCE.startPoller();}

init()方法最后调用了startPoller()，这里开启了一个守护线程，会一直循环从我们指定的目录下读取文件，然后放到FilterLoader中，从而实现了动态加载Filter的功能

public class FilterFileManager {void startPoller() {poller = new Thread("GroovyFilterFileManagerPoller") {public void run() {while (bRunning) {try {sleep(pollingIntervalSeconds * 1000);manageFiles();} catch (Exception e) {e.printStackTrace();}}}};poller.setDaemon(true);poller.start();}void manageFiles() throws Exception, IllegalAccessException, InstantiationException {List<File> aFiles = getFiles();processGroovyFiles(aFiles);}/*** puts files into the FilterLoader. The FilterLoader will only addd new or changed filters** @param aFiles a List<File>* @throws IOException* @throws InstantiationException* @throws IllegalAccessException*/void processGroovyFiles(List<File> aFiles) throws Exception, InstantiationException, IllegalAccessException {for (File file : aFiles) {FilterLoader.getInstance().putFilter(file);}}