用ajax实现的jsp二级联动下拉列表

package com.hailong.link; import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class GetAllCitys extends HttpServlet{ /** * 尹海龙 */ private static final long serialVersionUID = 1L; private String dbUser = "root";//声明数据库用户名 private String dbPassword = "1234";//声明数据库连接密码 private String dbDriver = "com.mysql.jdbc.Driver";//声明数据库驱动 private String dbConnection = "jdbc:mysql://localhost:3306/pclink";//声明数据库连接 private Connection con; public void init(ServletConfig config) throws ServletException { try { Class.forName(dbDriver); } catch (ClassNotFoundException e) { System.out.println("没有发现数据库驱动程序!"); } try { con = DriverManager.getConnection(dbConnection,dbUser,dbPassword); System.out.println("数据库驱动加载成功!"); } catch (SQLException e) { System.out.println("创建数据库连接失败!"); } } protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); String idStr = request.getParameter("parent_id"); response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); int parent_id; if(idStr != null && !"".equals(idStr)){ parent_id = Integer.parseInt(idStr); }else{ parent_id = 1; } String sql = "select id,content from pclink where parent_id = ?"; try { PreparedStatement pstmt = con.prepareStatement(sql); pstmt.setInt(1,parent_id); ResultSet rs = pstmt.executeQuery(); StringBuffer allCitys = new StringBuffer(); response.setContentType("text/xml"); allCitys.append("<?xml version=\"1.0\" encoding=\"utf-8\"?>"); allCitys.append("<allCitys>"); while (rs.next()) { allCitys.append("<city>"); allCitys.append("<cityId>"+rs.getInt("id")+"</cityId>"); allCitys.append("<cityName>"+rs.getString("content")+"</cityName>"); allCitys.append("</city>"); } allCitys.append("</allCitys>"); out.print(allCitys.toString()); } catch (SQLException e) { System.out.println("执行出现异常!"); } } public void destroy() { super.destroy(); } }