使用DWR开发AJAX For J2EE

package org.thj; import java.sql.Connection; import java.sql.ResultSet; import java.sql.Statement; public class UserDAO { public boolean exitUser(String username){ try{ Connection conn = DBConnection.getConnection(); Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery("select count(*) from user where username ='" + username +"'"); rs.next(); if(0 != rs.getInt(1)) return true; return false; }catch(Exception e){ System.out.println("DAO访问失败!"); return true; } } }