linux远程文件下载java.net.UnknownHostException解决办法

下载远程附件，本地windows都OK，但是放到sit测试环境Linux系统就抛异常了，下载链接为  http://sk.sit.fosuntech.cn/group1/M00/00/72/CqYKHVn69wyAMl6YAAVf953sp4Y075.pdf，

出问题的代码：

            URL url = new URL(downLoadPath);                URLConnection conn = url.openConnection();  

异常信息：

java.net.UnknownHostException: sk.sit.fosuntech.cn          at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_65]          at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_65]          at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_65]          at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection$6.run(HttpURLConnection.java:1675) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection$6.run(HttpURLConnection.java:1673) ~[na:1.7.0_65]          at java.security.AccessController.doPrivileged(Native Method) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.getChainedException(HttpURLConnection.java:1671) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1244) ~[na:1.7.0_65]          at com.fosun.credit.control.cms.loanapplication.RepaymentController.downloadAttachment(RepaymentController.java:544) ~[RepaymentController.class:na]          at sun.reflect.GeneratedMethodAccessor285.invoke(Unknown Source) ~[na:na]          at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_65]          at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_65]          at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) [spring-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778) [spring-webmvc-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) [servlet-api.jar:na]          at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) [servlet-api.jar:na]          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) [catalina.jar:7.0.27]          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.27]          at com.fosun.credit.filter.CrossFilter.doFilter(CrossFilter.java:36) [CrossFilter.class:na]          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.27]          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.27]          at com.common.base.filter.ControlLogFilter.doFilter(ControlLogFilter.java:38) [credit-base-0.0.1-SNAPSHOT.jar:na]          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.27]          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.27]          at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) [spring-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) [spring-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.27]          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.27]          at com.fosun.base.logTrace.servlet.filter.TraceNoFilter.doFilter(TraceNoFilter.java:30) [base-logTrace-0.0.1-SNAPSHOT.jar:na]          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.27]          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.27]          at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) [catalina.jar:7.0.27]          at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) [catalina.jar:7.0.27]          at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [catalina.jar:7.0.27]          at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) [catalina.jar:7.0.27]          at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) [catalina.jar:7.0.27]          at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) [catalina.jar:7.0.27]          at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) [catalina.jar:7.0.27]          at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) [catalina.jar:7.0.27]          at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999) [tomcat-coyote.jar:7.0.27]          at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) [tomcat-coyote.jar:7.0.27]          at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309) [tomcat-coyote.jar:7.0.27]          at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_65]          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_65]          at java.lang.Thread.run(Thread.java:745) [na:1.7.0_65]  Caused by: java.net.UnknownHostException: sk.sit.fosuntech.cn          at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178) ~[na:1.7.0_65]          at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.7.0_65]          at java.net.Socket.connect(Socket.java:579) ~[na:1.7.0_65]          at java.net.Socket.connect(Socket.java:528) ~[na:1.7.0_65]          at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.7.0_65]          at sun.net.www.http.HttpClient.openServer(HttpClient.java:432) ~[na:1.7.0_65]          at sun.net.www.http.HttpClient.openServer(HttpClient.java:527) ~[na:1.7.0_65]          at sun.net.www.http.HttpClient.<init>(HttpClient.java:211) ~[na:1.7.0_65]          at sun.net.www.http.HttpClient.New(HttpClient.java:308) ~[na:1.7.0_65]          at sun.net.www.http.HttpClient.New(HttpClient.java:326) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:996) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:932) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:850) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1300) ~[na:1.7.0_65]          at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(HttpURLConnection.java:2678) ~[na:1.7.0_65]          at java.net.URLConnection.getHeaderFieldLong(URLConnection.java:639) ~[na:1.7.0_65]          at java.net.URLConnection.getContentLengthLong(URLConnection.java:511) ~[na:1.7.0_65]          at com.fosun.credit.control.cms.loanapplication.RepaymentController.downloadAttachment(RepaymentController.java:538) ~[RepaymentController.class:na]          ... 41 common frames omitted

下载远程文件抛出异常 UnKnownHostException，百度了一些资料，原来是因为sk.sit.fosuntech.cn这个域名无法解析，最终的解决方案是：

1. ping www.baidu.com 是否能ping通，如果不能证明网络有问题

2. 如果能ping通，那估计就是服务器不支持域名解析，需要加配置，编辑 vi /etc/resolv.conf  ，加上 nameserver 8.8.8.8，

保存以后重启网络服务 ，service network restart，现在可以ping 通了。

如果还是不行，就给服务器配置域名IP对应地址  vi /etc/resolv.conf

在其中添加一条: 103.10.0.42 sk.sit.fosuntech.cn 保存