cas-client和cas server交互，cas server必须要有域名，否则会发生异常。
实际上这个问题发生在cas-client-core模块，包org.jasig.cas.client.util，类CommonUtils.java。
修改如下代码：
public static String getResponseFromServer(final URL constructedUrl, final HttpURLConnectionFactory factory,
final String encoding) {
HttpsURLConnection conn = null;
InputStreamReader in = null;
try {
HostnameVerifier hv = new HostnameVerifier() {
public boolean verify(String urlHostName, SSLSession session) {
return true;
}
};
HttpsURLConnection.setDefaultHostnameVerifier(hv);
conn = (HttpsURLConnection) constructedUrl.openConnection();
if (CommonUtils.isEmpty(encoding)) {
in = new InputStreamReader(conn.getInputStream());
} else {
in = new InputStreamReader(conn.getInputStream(), encoding);
}
final StringBuilder builder = new StringBuilder(255);
int byteRead;
while ((byteRead = in.read()) != -1) {
builder.append((char) byteRead);
}
return builder.toString();
} catch (final Exception e) {
LOGGER.error(e.getMessage(), e);
throw new RuntimeException(e);
} finally {
closeQuietly(in);
if (conn != null) {
conn.disconnect();
}
}
}