java.net.UnknownHostException解决

本文介绍了一种在启动系统时遇到的EHCache错误,并给出了具体的堆栈跟踪信息。该问题源于Java尝试获取本地主机名失败导致,解决方案为在/etc/hosts文件中添加主机IP和名称的映射。

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新上线的系统发现报如下错误

 at java.net.InetAddress.getLocalHost(InetAddress.java:1505) ~[na:1.8.0_92]
        at net.sf.ehcache.Cache.<clinit>(Cache.java:214) ~[ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.config.ConfigurationHelper.createCache(ConfigurationHelper.java:296) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.config.ConfigurationHelper.createDefaultCache(ConfigurationHelper.java:219) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.configure(CacheManager.java:777) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.doInit(CacheManager.java:476) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.init(CacheManager.java:392) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.<init>(CacheManager.java:265) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.newInstance(CacheManager.java:1097) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.newInstance(CacheManager.java:1073) [ehcache-2.7.4.jar:2.7.4]
        at net.sf.ehcache.CacheManager.create(CacheManager.java:1056) [ehcache-2.7.4.jar:2.7.4]
        at org.springframework.cache.ehcache.EhCacheManagerFactoryBean.afterPropertiesSet(EhCacheManagerFactoryBean.java:139) [spring-context-support-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:108) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1477) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1222) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:108) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1477) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1222) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.support.AbstractBeanFactoryPointcutAdvisor.getAdvice(AbstractBeanFactoryPointcutAdvisor.java:88) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.aspectj.AspectJProxyUtils.isAspectJAdvice(AspectJProxyUtils.java:67) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.aspectj.AspectJProxyUtils.makeAdvisorChainAspectJCapableIfNecessary(AspectJProxyUtils.java:49) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator.extendAdvisors(AspectJAwareAdvisorAutoProxyCreator.java:97) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findEligibleAdvisors(AbstractAdvisorAutoProxyCreator.java:89) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean(AbstractAdvisorAutoProxyCreator.java:69) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:330) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:293) [spring-aop-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:422) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1579) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755) [spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757) [spring-context-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480) [spring-context-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:434) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106) [spring-web-4.1.7.RELEASE.jar:4.1.7.RELEASE]
        at com.baidu.dsp.common.listener.ContextListener.contextInitialized(ContextListener.java:21) [ContextListener.class:na]
        at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5016) [catalina.jar:7.0.59]
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5524) [catalina.jar:7.0.59]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [catalina.jar:7.0.59]
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575) [catalina.jar:7.0.59]
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565) [catalina.jar:7.0.59]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_92]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_92]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_92]
        at java.lang.Thread.run(Thread.java:745) [na:1.8.0_92]
Caused by: java.net.UnknownHostException: kkl-kvm-disconf-web01: unknown error
        at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[na:1.8.0_92]
        at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928) ~[na:1.8.0_92]
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323) ~[na:1.8.0_92]
        at java.net.InetAddress.getLocalHost(InetAddress.java:1500) ~[na:1.8.0_92]
        ... 71 common frames omitted

解决方法

[root@kkl-kvm-disconf-web02 conf]# cd /etc
[root@kkl-kvm-disconf-web02 etc]# vim host

[root@kkl-kvm-disconf-web02 conf]# cd /etc
[root@kkl-kvm-disconf-web02 etc]# vim hosts
添加188.188.. kkl-kvm-disconf-web02
其中188.188..是linux主机的ip地址,kkl-kvm-disconf-web02是主机名
保存即可

### java.net.UnknownHostException 偶尔出现的原因及解决方法 #### 1. 原因分析 java.net.UnknownHostException 异常通常出现在 Java 程序尝试通过主机名解析 IP 地址时失败的情况下。偶尔出现这种异常可能与以下因素相关: - **DNS 配置问题**:DNS 服务器可能临时不可用,或者 DNS 缓存未及时更新[^1]。 - **网络波动**:网络连接不稳定可能导致域名解析失败[^2]。 - **主机文件配置错误**:如果系统 `/etc/hosts` 文件中存在错误的主机名映射,可能会导致间歇性解析失败[^3]。 - **超时设置不足**:在高延迟或低带宽的网络环境中,域名解析可能需要更长的时间,而默认的超时时间可能不足以完成解析[^4]。 #### 2. 解决方案 针对上述原因,可以采取以下措施来减少或避免 `java.net.UnknownHostException` 的偶尔出现: - **优化 DNS 配置**: 确保使用的 DNS 服务器稳定可靠,并定期检查其可用性。可以通过修改系统的 DNS 配置文件(如 `/etc/resolv.conf`)指定备用 DNS 服务器。 - **增加超时时间**: 在代码中显式设置更高的超时时间以适应网络环境的变化。例如,使用 `InetAddress` 类时,可以通过以下方式设置超时: ```java import java.net.InetAddress; import java.net.UnknownHostException; public class HostResolverWithTimeout { public static void main(String[] args) { String hostName = "example.com"; int timeout = 5000; // 设置超时时间为5秒 try { boolean resolved = InetAddress.getByName(hostName).isReachable(timeout); if (resolved) { System.out.println("Host is reachable: " + hostName); } else { System.err.println("Host is not reachable: " + hostName); } } catch (UnknownHostException e) { System.err.println("Failed to resolve host: " + hostName); } catch (Exception e) { e.printStackTrace(); } } } ``` - **检查 `/etc/hosts` 文件**: 确保 `/etc/hosts` 文件中正确配置了主机名与 IP 地址的映射关系。如果不需要自定义主机名映射,可以删除或注释掉不必要的条目。 - **启用 DNS 缓存**: 在应用程序中启用 DNS 缓存可以减少频繁的 DNS 查询次数,从而降低解析失败的概率。可以通过以下 JVM 参数启用 DNS 缓存: ``` -Dnetworkaddress.cache.ttl=60 // 设置缓存有效时间为60秒 -Dnetworkaddress.cache.negative.ttl=10 // 设置负向缓存有效时间为10秒 ``` - **日志记录与监控**: 增强异常处理的日志记录功能,以便在出现问题时能够快速定位原因。例如,在捕获 `UnknownHostException` 时记录详细的上下文信息。 #### 3. 示例代码改进 以下是一个改进后的代码示例,增加了超时设置和异常处理的日志记录: ```java import java.net.InetAddress; import java.net.UnknownHostException; public class EnhancedHostResolver { public static void main(String[] args) { String hostName = "nonexistenthostname.com"; // 替换为实际主机名 int timeout = 5000; // 设置超时时间为5秒 try { InetAddress inetAddress = InetAddress.getByName(hostName); if (inetAddress.isReachable(timeout)) { System.out.println("IP address of " + hostName + " is " + inetAddress.getHostAddress()); } else { System.err.println("Host is not reachable: " + hostName); } } catch (UnknownHostException e) { System.err.println("Failed to resolve host: " + hostName + ". Please check DNS configuration."); e.printStackTrace(); } catch (Exception e) { System.err.println("An unexpected error occurred while resolving host: " + hostName); e.printStackTrace(); } } } ``` ###
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