checkuser.java

一本jsp自学教材

package user;
import javax.sql.DataSource;
import java.sql.*;
public class CheckUser {
  public CheckUser(){
      } 
  public boolean userExist(String user,DataSource ds)
  {
    boolean flag=false;
    try{
      Connection conn = ds.getConnection();
      Statement stmt = conn.createStatement();
      String sql = "SELECT username FROM user WHERE username='" + user + "'";
      ResultSet rs = stmt.executeQuery(sql);
      if (rs.next()) {
        flag = true;
      }
      rs.close();
      stmt.close();
      conn.close();
    }
    catch(Exception e){
      System.out.print(e.toString());
    }
    return flag;
  }
}