我是 spring 框架的新生。我从 start.spring.io 生成项目，现在尝试运行它。当我尝试时，我必须面对以下异常，（我使用 TomCat 服务器）请给出解决方案，
===========================异常====================== =======
G:\courses\Course-projects\spring-projects\S5Guru\spring5webapp>mvnw spring-boot:run
Exception in thread "main" java.net.UnknownHostException: repo.maven.apache.org
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:668)
at sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:173)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:432)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:527)
at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:264)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1138)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1032)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1546)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)
at org.apache.maven.wrapper.DefaultDownloader.downloadInternal(DefaultDownloader.java:90)
at org.apache.maven.wrapper.DefaultDownloader.download(DefaultDownloader.java:76)
at org.apache.maven.wrapper.Installer.createDist(Installer.java:72)
at org.apache.maven.wrapper.WrapperExecutor.execute(WrapperExecutor.java:121)
at org.apache.maven.wrapper.MavenWrapperMain.main(MavenWrapperMain.java:61)