title: Exception in thread "main" java.net.UnknownHostException: repo.maven.apache.org
body: <p>I'm a freshman for the spring framework. I generate project from start.spring.io and now I try to run it.
  when I try it, I have to face following exception,
  (I use TomCat server)
  plz..give solution for this,</p>
  
  <p>===========================Exception=============================</p>
  
  <pre><code>G:\courses\Course-projects\spring-projects\S5Guru\spring5webapp&gt;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.&lt;init&gt;(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)
  
  </code></pre>