public class userdao {
 private connection conn = null;
 private preparedstatement ps=null;
 private int result=0;
 private resultset rs=null;

 //用戶注冊(cè)
 public int register(user user){
 string sql="insert into users(name,password,age) value (?,?,?)";
 try {
 //獲取數(shù)據(jù)庫(kù)連接對(duì)象
 conn= jdbcutil.getconnection();
 //獲取數(shù)據(jù)庫(kù)操作對(duì)象
 ps=conn.preparestatement(sql);
 ps.setstring(1,user.getname());
 ps.setstring(2,user.getpassword());
 ps.setint(3,user.getage());
 //執(zhí)行sql
 result=ps.executeupdate();
 } catch (exception e) {
 e.printstacktrace();
 }finally {
 jdbcutil.close(null,ps,conn);
 }
 return result;
 }

 //登錄驗(yàn)證用戶信息
 public int login(string username,string password){
 string sql ="select count(*) from users where name=? and password=?";
 try {
 conn=jdbcutil.getconnection();
 ps=conn.preparestatement(sql);
 ps.setstring(1,username);
 ps.setstring(2,password);
 rs=ps.executequery();
 while (rs.next()){
 result=rs.getint("count(*)");
 }
 } catch (exception e) {
 e.printstacktrace();
 } finally {
 jdbcutil.close(rs,ps,conn);
 }
 return result;
 }

 //根據(jù)用戶名 顯示用戶名、密碼、年齡
 public user findbyname(string username){
 string sql="select name,password,age from users where name=?";
 user user = null;
 try {
 conn=jdbcutil.getconnection();
 ps=conn.preparestatement(sql);
 ps.setstring(1,username);
 rs=ps.executequery();
 while (rs.next()){
 string name = rs.getstring("name");
 string password = rs.getstring("password");
 int age = rs.getint("age");
 user = new user(name,password,age);
 }

 } catch (exception e) {
 e.printstacktrace();
 }finally {
 jdbcutil.close(null,ps,conn);
 }
 return user;
 }
}

public class user {
 private int id;
 private string name;
 private string password;
 private int age;
//set...
//get...
//constructor...
}

public class userserviceimpl implements userservice {
 userdao userdao = new userdao();
 // 注冊(cè)
 @override
 public int register(user user) {
 return userdao.register(user);
 }
 // 登陸
 @override
 public int login(string username, string password) {
 return userdao.login(username,password);
 }

 // 根據(jù)用戶名查找信息
 @override
 public user findbyname(string username) {
 return userdao.findbyname(username);
 }
}

// findbynameservlet
public class findbynameservlet extends httpservlet {
 protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 string name = request.getparameter("name");

 userservice userservice = new userserviceimpl();
 user user = userservice.findbyname(name);

 //將查詢結(jié)果放入request作用域
 request.setattribute("userinfo",user);
 request.getrequestdispatcher("/jsp/index.jsp").forward(request,response);
 }
}

// loginservlet
public class loginservlet extends httpservlet {
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 //1 獲取
 string username = request.getparameter("username");
 string password = request.getparameter("password");

 //2 service調(diào)用dao對(duì)數(shù)據(jù)庫(kù)操作
 userservice userservice = new userserviceimpl();
 int result = userservice.login(username, password);

 //3 成功跳轉(zhuǎn)到查詢頁(yè)面，失敗跳轉(zhuǎn)到失敗頁(yè)面
 if (result>0){
 response.sendredirect("/jsp/index.jsp");
 }else{
 response.sendredirect("/login_error.html");
 }
 }
}
// registerservlet
public class registerservlet extends httpservlet {
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 userservice userservice = new userserviceimpl();
 user user = null;
 int result = 0;
 //1【調(diào)用請(qǐng)求對(duì)象】讀取【請(qǐng)求頭】參數(shù)信息，得到用戶注冊(cè)信息
 string username, password, age;
 username = request.getparameter("username");
 password = request.getparameter("password");
 age = request.getparameter("age");
 user = new user(username, password, integer.valueof(age));
 //2 調(diào)用userservice——>userdao
 // 先查詢用戶是否存在
 user byname = userservice.findbyname(username);
 if (byname!=null){
 request.setattribute("info","用戶已存在！");
 request.getrequestdispatcher("/jsp/register.jsp").forward(request,response);
 }
 // 注冊(cè)
 result = userservice.register(user);

 //3 設(shè)置編碼格式，防止亂碼
 response.setcontenttype("text/html;charset=utf-8");
 printwriter out = response.getwriter();

 //注冊(cè)成功：——>跳轉(zhuǎn)至登錄頁(yè)面進(jìn)行登錄
 //注冊(cè)失敗：——>注冊(cè)頁(yè)面提示：注冊(cè)失敗
 if (result == 1) {
 response.sendredirect("/login.html");
 } else {
 request.setattribute("info","注冊(cè)失??！");
 request.getrequestdispatcher("/jsp/register.jsp").forward(request,response);
 }
 }
}

public class jdbcutil {
 private jdbcutil(){}
 //靜態(tài)代碼塊在類加載時(shí)執(zhí)行，并且執(zhí)行一次。
 static{
 try {
 class.forname("com.mysql.cj.jdbc.driver");
 } catch (classnotfoundexception e) {
 e.printstacktrace();
 }
 }
 //獲取數(shù)據(jù)庫(kù)連接對(duì)象
 public static connection getconnection() throws exception{
 string url="jdbc:mysql://127.0.0.1:3306/zy?&usessl=false&servertimezone=utc&rewritebatchedstatements=true";
 string user="root";
 string password="rootroot";

 return drivermanager.getconnection(url,user,password);
 }
 /**
 *關(guān)閉資源
 * @param conn 連接對(duì)象
 * @param ps 數(shù)據(jù)庫(kù)操作對(duì)象
 * @param rs 結(jié)果集
 */
 public static void close(resultset rs, statement ps, connection conn){
 if (rs != null) {
 try {
 rs.close();
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 }
 if (ps != null) {
 try {
 ps.close();
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 }
 if (conn != null) {
 try {
 conn.close();
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 }
 }
}

<%@ page import="entity.user" %>
<%@ page contenttype="text/html;charset=utf-8" language="java" %>


 查詢頁(yè)面 

 
輸入用戶名，查詢信息
         <%
 user userinfo = (user) request.getattribute("userinfo");
 %>
 <%
 if (userinfo != null) {
 %>
 

 

 
用戶名
 
密碼
 
年齡
 
 

 
     <%=userinfo.getname()%>    
 
     <%=userinfo.getpassword()%>    
 
     <%=userinfo.getage()%>    
 
 

 <%
 }
 %>

<%@ page import="com.mysql.cj.util.stringutils" %>
<%@ page contenttype="text/html;charset=utf-8" language="java" %>


 title <%
 string info =(string) request.getattribute("info");
%>
<%
 if (!stringutils.isnullorempty(info)){
%>
 
<%=info%>
<%
 }
%>

   

 

 
用戶名
 

 
 

 
密碼
 

 
 

 
年齡
 

 
 

 

       
 
 

  

    loginservlet  servlet.loginservlet      registerservlet  servlet.registerservlet      findbynameservlet  servlet.findbynameservlet      loginservlet  /login      registerservlet  /register      findbynameservlet  /findbyname    
   login.html