利用JDBC对数据库的基本操作

public class UserDaoImpl implements IUserDao {

 public boolean login(String username, String password) throws SQLException {
  Connection con = ConnectionUtil.getConnection();
  Statement st = null;
  ResultSet rs=null;
  boolean loginFlag = false;
  try {
   String sql = "select * from tb_userinfo where username='"+username+"' and password='"+password+"'";
   st=con.createStatement();
   rs=st.executeQuery(sql);
   while(rs.next()){
    loginFlag=true;
   }
   
  } catch (SQLException e) {

   e.printStackTrace();
  }finally{
   ConnectionUtil.closeRs(rs);
   ConnectionUtil.closeSt(st);
   ConnectionUtil.closeCon(con);
  }

  return loginFlag;
 }

 public List getCerAddress() throws SQLException {
  
  Connection con=ConnectionUtil.getConnection();
  Statement st = null;
  ResultSet rs = null;
  List ls = new ArrayList();
  String regCerAddress = "";
  String valCerAddress="";
  try{
   String sql="select * from tb_ceraddress";
   st = con.createStatement();
   rs = st.executeQuery(sql);
   while(rs.next()){
    regCerAddress = rs.getString(1);
    valCerAddress =  rs.getString(2);
   }
   ls.add(0, regCerAddress);
   ls.add(1,valCerAddress);
  }catch(Exception e){
   e.printStackTrace();
  }finally{
   ConnectionUtil.closeRs(rs);
   ConnectionUtil.closeSt(st);
   ConnectionUtil.closeCon(con);
  }
  return ls;
 }

}