今天部署應用到Tomcat，發現啟動過程中有異常，驗證碼前臺出不來，以為是此異常導致的，後來解決了java.net.UnknownHostException，登入頁面的驗證碼還是出不來不知是何問題。

詳細異常輸出

報錯方式：java.net.UnknownHostException: 主機名: 主機名

1. java.net.UnknownHostException: RD-CD-APP122.wlyd.local: RD-CD-APP122.wlyd.local: ?..?..縐版.?..  
2.     at java.net.InetAddress.getLocalHost(InetAddress.java:1473)  
3.     at net.sf.ehcache.Cache.<clinit>(Cache.java:214)  
4.     at net.sf.ehcache.config.ConfigurationHelper.createCache(ConfigurationHelper.java:296)  
5.     at net.sf.ehcache.config.ConfigurationHelper.createDefaultCache(ConfigurationHelper.java:219)  
6.     at net.sf.ehcache.CacheManager.configure(CacheManager.java:722)  
7.     at net.sf.ehcache.CacheManager.doInit(CacheManager.java:439)  
8.     at net.sf.ehcache.CacheManager.init(CacheManager.java:377)  
9.     at net.sf.ehcache.CacheManager.<init>(CacheManager.java:259)  
10.     at net.sf.ehcache.CacheManager.newInstance(CacheManager.java:1037)  
11.     at net.sf.ehcache.CacheManager.newInstance(CacheManager.java:818)  
12.     at net.sf.ehcache.CacheManager.create(CacheManager.java:799)  
13.     at com.wlyd.fmcgwms.util.ehcache.EhcacheUtil.<clinit>(EhcacheUtil.java:18)  
14.     at com.wlyd.fmcgwms.util.sysinit.InitSysProperties.setApplicationContext(InitSysProperties.java:55)  
15.     at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:117)  
16.     at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:92)  
17.     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:396)  
18.     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1505)  
19.     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:521)  
20.     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)  
21.     at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)  
22.     at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)  
23.     at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)  
24.     at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)  
25.     at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)  
26.     at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)  
27.     at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)  
28.     at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389)  
29.     at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294)  
30.     at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)  
31.     at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4994)  
32.     at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5492)  
33.     at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)  
34.     at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)  
35.     at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)  
36.     at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:649)  
37.     at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1081)  
38.     at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1877)  
39.     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)  
40.     at java.util.concurrent.FutureTask.run(FutureTask.java:262)  
41.     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)  
42.     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)  
43.     at java.lang.Thread.run(Thread.java:745)  
44. Caused by: java.net.UnknownHostException: RD-CD-APP122.wlyd.local: ?..?..縐版.?..  
45.     at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)  
46.     at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:901)  
47.     at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1293)  
48.     at java.net.InetAddress.getLocalHost(InetAddress.java:1469)  
49.     ... 41 more  
50. 2016-12-29 17:11:38,875 [localhost-startStop-1] INFO  [org.quartz.core.SchedulerSignalerImpl] - Initialized Scheduler Signaller of type: class org.quartz.core.SchedulerSignalerImpl  
51. 2016-12-29 17:11:38,885 [localhost-startStop-1] INFO  [org.quartz.core.QuartzScheduler] - Quartz Scheduler v.1.8.5 created.  
52. 2016-12-29 17:11:38,886 [localhost-startStop-1] INFO  [org.quartz.simpl.RAMJobStore] - RAMJobStore initialized.  
53. 2016-12-29 17:11:38,888 [localhost-startStop-1] INFO  [org.quartz.core.QuartzScheduler] - Scheduler meta-data: Quartz Scheduler (v1.8.5) 'SpringJobSchedulerFactoryBean' with instanceId 'NON_CLUSTERED'  
54.   Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.  
55.   NOT STARTED.  
56.   Currently in standby mode.  
57.   Number of jobs executed: 0  
58.   Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 10 threads.  
59.   Using job-store 'org.quartz.simpl.RAMJobStore' - which does not support persistence. and is not clustered.  

解決方法

命令：vi /etc/hosts

在最後一行新增：127.0.0.1 主機名。我的系統改成了如下圖所示：

修改完成，儲存檔案，之後就不會有此異常發生了。