SEVLET

Question

写了如下 程序：
package PLoginServlet;
import java.sql.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class LoginServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet{
    public LoginServlet(){
        super();
     }
    protected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
    
        }
    protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
         response.setContentType("text/html");
         String result="";
         String strUserName=request.getParameter("txtUserName");
         String strPassword=request.getParameter("txtPassword");
         if((strUserName==null)||(strUserName.equals(""))||(strUserName.length()>12))  {
              result="请输入用户名(不超过12字符)";
              request.setAttribute("error_username",result);
              response.sendRedirect("index.jsp");
          }
         if((strPassword==null)||(strPassword.equals(""))||(strPassword.length()>12))  {
              result="请输入密码(不超过12字符)";
              request.setAttribute("error_username",result);
              response.sendRedirect("index.jsp");
          }
         String url="jdbc:sqlserver://localhost;databaseName=LearnJSP;user=sa;password=";
         Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
         Connection con=DriverManager.getConnection(url);
         Statement stmt=null;
         ResultSet rs=null;
         try{
           String sql="select * from UserInfo where UserName='"+strUserName+"' and UserPwd='"+strPassword+"'";
           stmt=con.createStatement();
           rs=stmt.executeQuery(sql);
           if(rs.next()) {
             request.getSession(true).setAttribute("UserName",strUserName);
             response.sendRedirect("login_success.jsp");
           }
           else{
              response.sendRedirect("login_failure.jsp");
           }
         }
         catch(SQLException sqlExc){
           sqlExc.printStackTrace();
         }
         catch(Exception e){
            e.printStackTrace();
         }
         finally{
            try{
               if(rs!=null) {rs.close();}
               if(stmt!=null) {stmt.close();}
               con.close();
            }
            catch(SQLException sqlExc){
               sqlExc.printStackTrace();
            }
         }
       
     }
}
提示如下错误：
LoginServlet.java:29: unreported exception java.lang.ClassNotFoundException; mus
t be caught or declared to be thrown
                    Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver"
);
                                 ^
LoginServlet.java:30: unreported exception java.sql.SQLException; must be caught
 or declared to be thrown
                    Connection con=DriverManager.getConnection(url);
                                                              ^
2 errors
请高人赐教

Answer 1

这两句要写入trycatch语句块，因为可能会产生异常。

Answer 2

即使确定不可能产生异常也必须写入trycatch块，因为编译器可不知道你SQL Server是否正常，它只能假设一切皆有可能发生。