当配置中心要求高可用的时候，集群是一种不错的解决办法。当配置中心进行集群的时候，Zuul就派上了用场。并且Apollo和SpringCloud中zuul结合非常的方便，此处只解释在结合网关中路由刷新的部分原理：
前提：在Apollo的Portal的某个项目下存在公共的路由配置命名空间。如下图：
核心代码：
package cn.springcloud.book.zuul.config;
import com.ctrip.framework.apollo.model.ConfigChangeEvent;
import com.ctrip.framework.apollo.spring.annotation.ApolloConfigChangeListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
import org.springframework.cloud.netflix.zuul.RoutesRefreshedEvent;
import org.springframework.cloud.netflix.zuul.filters.RouteLocator;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
@Component
public class ZuulPropertiesRefresher implements ApplicationContextAware {
private static final Logger logger = LoggerFactory.getLogger(ZuulPropertiesRefresher.class);
private ApplicationContext applicationContext;
@Autowired
private RouteLocator routeLocator;
@ApolloConfigChangeListener(value = "TEST1.zuul-config")
public void onChange(ConfigChangeEvent changeEvent) {
boolean zuulPropertiesChanged = false;
for (String changedKey : changeEvent.changedKeys()) {
if (changedKey.startsWith("zuul.")) {
zuulPropertiesChanged = true;
break;
}
}
if (zuulPropertiesChanged) {
refreshZuulProperties(changeEvent);
}
}
private void refreshZuulProperties(ConfigChangeEvent changeEvent) {
logger.info("Refreshing zuul properties!");
/**
* rebind configuration beans, e.g. ZuulProperties
* @see org.springframework.cloud.context.properties.ConfigurationPropertiesRebinder#onApplicationEvent
*/
//核心代码一；
this.applicationContext.publishEvent(new EnvironmentChangeEvent(changeEvent.changedKeys()));
/**
* refresh routes
* @see org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration.ZuulRefreshListener#onApplicationEvent
*/
//核心代码二；
this.applicationContext.publishEvent(new RoutesRefreshedEvent(routeLocator));
logger.info("Zuul properties refreshed!");
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
如上配置路由刷新的核心代码实际上是采用我们常说的观察者，或者发布-订阅模型来实现的，上面的核心代码一和核心代码二实际上就是时间发布者。
如核心代码以对应的监听者如下：
/*
* Copyright 2013-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.context.properties;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationListener;
import org.springframework.core.env.Environment;
import org.springframework.jmx.export.annotation.ManagedAttribute;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedResource;
import org.springframework.stereotype.Component;
/**
* Listens for {@link EnvironmentChangeEvent} and rebinds beans that were bound to the
* {@link Environment} using {@link ConfigurationProperties
* <code>@ConfigurationProperties</code>}. When these beans are re-bound and
* re-initialized the changes are available immediately to any component that is using the
* <code>@ConfigurationProperties</code> bean.
*
* @see RefreshScope for a deeper and optionally more focused refresh of bean components
*
* @author Dave Syer
*
*/
@Component
@ManagedResource
public class ConfigurationPropertiesRebinder
implements ApplicationContextAware, ApplicationListener<EnvironmentChangeEvent> {
private ConfigurationPropertiesBeans beans;
private ApplicationContext applicationContext;
private Map<String, Exception> errors = new ConcurrentHashMap<>();
public ConfigurationPropertiesRebinder(ConfigurationPropertiesBeans beans) {
this.beans = beans;
}
@Override
public void setApplicationContext(ApplicationContext applicationContext)
throws BeansException {
this.applicationContext = applicationContext;
}
/**
* A map of bean name to errors when instantiating the bean.
*
* @return the errors accumulated since the latest destroy
*/
public Map<String, Exception> getErrors() {
return this.errors;
}
@ManagedOperation
public void rebind() {
this.errors.clear();
for (String name : this.beans.getBeanNames()) {
rebind(name);
}
}
@ManagedOperation
public boolean rebind(String name) {
if (!this.beans.getBeanNames().contains(name)) {
return false;
}
if (this.applicationContext != null) {
try {
Object bean = this.applicationContext.getBean(name);
if (AopUtils.isAopProxy(bean)) {
bean = getTargetObject(bean);
}
if (bean != null) {
this.applicationContext.getAutowireCapableBeanFactory().destroyBean(bean);
this.applicationContext.getAutowireCapableBeanFactory()
.initializeBean(bean, name);
return true;
}
}
catch (RuntimeException e) {
this.errors.put(name, e);
throw e;
}
catch (Exception e) {
this.errors.put(name, e);
throw new IllegalStateException("Cannot rebind to " + name, e);
}
}
return false;
}
@SuppressWarnings("unchecked")
private static <T> T getTargetObject(Object candidate) {
try {
if (AopUtils.isAopProxy(candidate) && (candidate instanceof Advised)) {
return (T) ((Advised) candidate).getTargetSource().getTarget();
}
}
catch (Exception ex) {
throw new IllegalStateException("Failed to unwrap proxied object", ex);
}
return (T) candidate;
}
@ManagedAttribute
public Set<String> getBeanNames() {
return new HashSet<String>(this.beans.getBeanNames());
}
//这段代码即上述核心代码一所发布事件的的监听方法。
@Override
public void onApplicationEvent(EnvironmentChangeEvent event) {
if (this.applicationContext.equals(event.getSource())
// Backwards compatible
|| event.getKeys().equals(event.getSource())) {
rebind();
}
}
}
