为什么会有java.sql.SQLException: No suitable driver的错误?在线等

java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getConnection(DriverManager.java:545)
at java.sql.DriverManager.getConnection(DriverManager.java:171)
at app.bean.DataBaseConnection.getConnection(DataBaseConnection.java:16)
at app.action.RegisterBean.<init>(RegisterBean.java:14)
at app.action.RegisterAction.execute(RegisterAction.java:25)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:226)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:415)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)我已经把3个sqlserver的驱动拷到/web-inf/lib下,在jre/lib/ext下也拷进去了，并且在java build path-library-add external jars也包含进这3个jar了。为什么还报错？开发工具是eclipseDataBaseConnection.java
import java.sql.Connection;
import java.sql.DriverManager;public class DataBaseConnection {
public static Connection getConnection(){
Connection con=null;
String CLASSFORNAME="com.microsoft.jdbc.sqlserver.SQLServerDriver";
String SERVANDDB="jdbc:microsoft.sqlserver://127.0.0.1:1433;DatabaseName=jspdev";
String USER="bn";
String PWD="bn";

try{
Class.forName(CLASSFORNAME);
con=DriverManager.getConnection(SERVANDDB,USER,PWD);
System.out.println("connect success");
}catch(Exception e){
System.out.println("connecting failded");
e.printStackTrace();
}
return con;
}}