ajax的操作步骤和代码实现

}if("2".equals(flag)){getAllUsersMessage(request,response);}if("3".equals(flag)){getAllUsersMessageById(request,response);}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request,response);}public void getAllUsers(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {List list = tance().getUsers();ribute("list", list);uestDispatcher("/").forward(request, response);return;}public void getAllUsersMessage(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String id = ameter("id");User user = tance().getUserById(nt(id));ribute("user", user);uestDispatcher("/").forward(request, response);return;}public void getAllUsersMessageById(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String id = ameter("id");

// TODO Auto-generated catch tackTrace();}finally{ll(conn, st, rs);}return list;}public User getUserById(int id){User user = null;Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;String sql ="select * from user where id=?";conn =n();try {ps = eStatement(sql);(1, id);rs = eQuery();while(()){user = new User();il(ing("email"));rname(ing("username"));swd(ing("passwd"));(("sex"));(("id"));}} catch (SQLException e) {// TODO Auto-generated catch tackTrace();}finally{ll(conn, ps, rs);}return user;}

package t;import ption;import riter;import ;import tException;import rvlet;import rvletRequest;import rvletResponse;import o;import ;public class UserManagerServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {UserDao dao = new UserDao();List list = User();ribute("list", list);uestDispatcher("/").forward(request, response);return;}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

<%@ page language="java" import=".*" pageEncoding="UTF-8"%><%@ taglib prefix="c" uri="/jsp/jstl/core"%><%String path = textPath();String basePath = eme()+"://"+verName()+":"+verPort()+path+"/";%>

//}//private static NewsDao newsdao=null;//public static NewsDao getInstance(){// if(newsdao==null){// newsdao=new NewsDao();// }// return newsdao;//}public List getNews(int type,int startRow,int size){List list = new ArrayList();News news = null;Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;String sql = "select * from news where type=? order by id desc limit ?,?";conn = n();try {ps = eStatement(sql);(1,type );(2, startRow);(3, size);rs = eQuery();while(()){news = new News();time(e("addtime"));hor(ing("author"));tent(ing("content"));(("id"));el(("isdel"));le(ing("title"));e(("type"));(news);}} catch (SQLException e) {

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<%@ page language="java" import=".*" pageEncoding="UTF-8"%><%@ taglib prefix="c" uri="/jstl/core_rt" %><%String path = textPath();String basePath = eme()+"://"+verName()+":"+verPort()+path+"/";%>

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省：select * from chinacity where citypostcode like '__0000';select * from chinacity where substr(citypostcode,3,4)='0000';市：select * from chinacity where citypostcode like '41__00' and citypostcode <>'410000'级联菜单：省，市，区：例package ;import tion;import edStatement;import Set;import eption;import ent;import ist;import ;import ity;import ;public class ChinaCityDao {public List getProvince(){List list = new ArrayList();//因为是要查询多个chinacity的信息，所以放在List中

ChinaCity chinacity = null;Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;String sql = "select * from chinacity where citypostcode like '__0000'";conn = n();try {ps = eStatement(sql);rs = eQuery();while(()){chinacity = new ChinaCity();yid(("cityid"));yname(ing("cityname"));ypostcode(ing("citypostcode"));(chinacity);}} catch (SQLException e) {// TODO Auto-generated catch tackTrace();}finally{ll(conn, ps, rs);}return list;}public List getCity(String citypostcode){List list = new ArrayList();ChinaCity chinacity = null;Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;String sql = "select * from chinacity where citypostcode like ? and citypostcode <>?";conn = n();try {ps = eStatement(sql);

ing(1, ing(0,2)+"__00");ing(2, citypostcode);rs = eQuery();while(()){chinacity = new ChinaCity();yid(("cityid"));yname(ing("cityname"));ypostcode(ing("citypostcode"));(chinacity);}} catch (SQLException e) {// TODO Auto-generated catch tackTrace();}finally{ll(conn, ps, rs);}return list;}public List getArea(String citypostcode){List list = new ArrayList();ChinaCity chinacity = null;Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;//String sql = "select * from chinacity where citypostcode like ? and citypostcode <>?";String sql = "select * from chinacity where substr(citypostcode,1,4)=? and citypostcode<>?";conn = n();try {ps = eStatement(sql);//ing(1, ing(0,4)+"__");//从第0个位置上开始截取，截取到第4-1个位置上ing(1, ing(0,4));ing(2, citypostcode);rs = eQuery();while(()){

chinacity = new ChinaCity();yid(("cityid"));yname(ing("cityname"));ypostcode(ing("citypostcode"));(chinacity);}} catch (SQLException e) {// TODO Auto-generated catch tackTrace();}finally{ll(conn, ps, rs);}return list;}}<%@ page language="java" import=".*" pageEncoding="UTF-8"%><%String path = textPath();String basePath = eme()+"://"+verName()+":"+verPort()+path+"/";%>

var option = new Option(data[i].cityname,data[i].citypostcode);(option);}});}

//要通过value值的改变选择相应的省对应的市 请选择省 请选择市 请选择区