到主机 的 TCP/IP 连接失败。 java.net.ConnectException: Connection refused: connect,该如何处理

public class ConnDB {    public Connection conn=null;    public Statement stmt=null;    public ResultSet rs=null;    private static String propFileName="/com/connDB.properties";    private static Properties prop=new Properties();    private static String dbClassName="com.microsoft.sqlserver.jdbc.SQLServerDriver";//com.microsoft.jdbc.sqlserver.SQLServerDriver    private static String dbUrl="jdbc:sqlserver://127.0.0.1:1422;DatabaseName=OnLineExam";    private static String dbUser="sa";    private static String dbPwd="123";        public static Connection getConnection()    {        Connection conn=null;        try        {            Class.forName(dbClassName).newInstance();            conn=DriverManager.getConnection(dbUrl,dbUser,dbPwd);        }        catch(Exception e)        {            e.printStackTrace();        }        if(conn==null)        {            System.err.println("数据库连接失败!");        }        return conn;    }}

com.microsoft.sqlserver.jdbc.SQLServerException: 到主机  的 TCP/IP 连接失败。 java.net.ConnectException: Connection refused: connect    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(Unknown Source)    at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(Unknown Source)    at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(Unknown Source)    at java.sql.DriverManager.getConnection(DriverManager.java:582)    at java.sql.DriverManager.getConnection(DriverManager.java:185)    at com.hs.core.ConnDB.getConnection(ConnDB.java:40)    at com.hs.core.ConnDB.excuteQuery(ConnDB.java:56)    at com.hs.dao.StudentDAO.checkStudent(StudentDAO.java:17)    at com.hs.action.StudentAction.studentLogin(StudentAction.java:64)    at com.hs.action.StudentAction.execute(StudentAction.java:26)    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at com.hs.core.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:39)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)    at java.lang.Thread.run(Thread.java:619)数据库连接失败!2010-2-24 17:00:37 org.apache.struts.action.RequestProcessor processException警告: Unhandled Exception thrown: class java.lang.NullPointerException2010-2-24 17:00:37 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet action threw exceptionjava.lang.NullPointerException    at com.hs.core.ConnDB.excuteQuery(ConnDB.java:57)    at com.hs.dao.StudentDAO.checkStudent(StudentDAO.java:17)    at com.hs.action.StudentAction.studentLogin(StudentAction.java:64)    at com.hs.action.StudentAction.execute(StudentAction.java:26)    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at com.hs.core.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:39)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)    at java.lang.Thread.run(Thread.java:619)