AJax验证用户名是否存在

package com.accp.ajax.dwr; import java.sql.*; public class Tools { Connection connection = null; ResultSet resultset = null; Statement statement = null; PreparedStatement pstmt = null; public Tools() { } public Connection getConnection() { try { Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver"); connection = DriverManager .getConnection( "jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=Ajax", "sa", ""); } catch (Exception e) { System.out.println("@error--getConnection():" + e.getMessage()); } return connection; } public ResultSet executeQuery(String sql) { try { connection = this.getConnection(); statement = connection.createStatement(); resultset = statement.executeQuery(sql); System.out.println("sql statement-->" + sql); } catch (Exception e) { System.out.println("@error--executeQuery():" + e.getMessage()); } return resultset; } public void closedb() { try { if (resultset != null) { resultset.close(); resultset = null; } if (statement != null) { statement.close(); statement = null; } if (pstmt != null) { pstmt.close(); pstmt = null; } if (connection != null) { connection.close(); connection = null; } } catch (Exception e) { System.out.println("@error--closedb():" + e.getMessage()); } } public static String trans(String chi) { String result = null; try { byte temp[] = chi.getBytes("iso-8859-1"); result = new String(temp); } catch (Exception e) { System.out.println(e.toString()); } return result; } public String check(String name) { try { this.connection = this.getConnection(); String sql = "select * from userinfo where name=?"; pstmt = connection.prepareStatement(sql); pstmt.setString(1, trans(name)); ResultSet rs = pstmt.executeQuery(); if (rs.next()) { return "对不起！该用户名已经存在！"; } else { return "恭喜！您可以使用此名称！"; } } catch (Exception ex) { System.out.println("错误：" + ex.getMessage()); return "error"; } finally { this.closedb(); } } // public static void main(String args[]) { // Tools t = new Tools(); // // System.out.println(t.check("lisi")); // // } }