一个用户注册登陆的系统，用到了MD5加密处理密码，实现了一个简单的数据库连接池connectionPool,
实现了注册，登陆，登陆之后修改用户信息等功能，非常适合初学者
一.准备工作
数据库：MySQL 5.5.62-log MySQL Community Server (GPL)
创建user表，数据库为first_db;
CREATE TABLE IF NOT EXISTS `user`(
`user_id` INT UNSIGNED AUTO_INCREMENT,
`username` VARCHAR(100) NOT NULL,
`password` VARCHAR(100) NOT NULL,
`phone` VARCHAR(100) NOT NULL, PRIMARY KEY ( `user_id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
二.项目结构图：
三.部分核心代码
web.xml：
实现servlet指向CheckUser类和UpdateUser类，指定login.jsp为首页
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<servlet>
<servlet-name>CheckUser</servlet-name>
<servlet-class>com.Account.CheckUser</servlet-class>
</servlet>
<servlet>
<servlet-name>UpdateUser</servlet-name>
<servlet-class>com.Account.UpdateUser</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckUser</servlet-name>
<url-pattern>/CheckUser</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>UpdateUser</servlet-name>
<url-pattern>/UpdateUser</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list>
</web-app>login.jsp:
login.jsp是登陆页面，from表单中加了一个<input type="hidden" name="actiontype" value="login" />的隐藏按钮，用于在CheckUser类中判断是登陆还是注册，通过actiontype的值。点击登陆，根据servlet分发到CheckUser类处理请求
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<title>登陆</title>
</head>
<body>
<h2>欢迎登陆</h2>
<form action="CheckUser" method="post">
账号:<input type="text" name="userName"><br/>
密码:<input type="password" name="password"><br/>
<input type="hidden" name="actiontype" value="login" /> <!-- 用隐藏域来判断登陆还是注册 -->
<input type="submit" value="登陆"/><br/><br />
</form>
<button onclick="window.location='register.jsp'">注册</button>
${sessionScope.errorMsg} <!-- EL语法--获取session的errorMsg并显示 -->
</body>
</html>CheckUser.java:
实现处理登陆注册的请求 向数据库请求并返回结果
package com.Account;
import java.io.IOException;
import java.sql.Connection;
//import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@SuppressWarnings("serial")
public class CheckUser extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
String userName = request.getParameter("userName");
String password = request.getParameter("password");
//md5对密码加密
Md5 md5=new Md5();
//判断类型是登陆还是注册
String Sql="";
String action_type = request.getParameter("actiontype");
if(action_type.equals("login")){
Sql = "SELECT user_id,username,password,phone FROM user "
+ "where username='" + userName+ "' AND password='" + md5.MD5(password) + "' ";
}else if(action_type.equals("register")){
Sql = "INSERT into user (username,password,phone) values ('"+ userName+"' ,'"+md5.MD5(password) +"',' ')";
}
Connection connection = null;
PreparedStatement preSta = null;
ResultSet rs = null;
// 建立连接,DriverManager是JDBC的管理层
try {
//使用连接池的方式连接数据库
ConnectionPool.setUrl(ConnectionPool.getUrl());
ConnectionPool.setUser(ConnectionPool.getUser());//DBTools.getDatabaseUserName()
ConnectionPool.setPassword(ConnectionPool.getPassword());
connection = ConnectionPool.getConnection();
preSta = connection.prepareStatement(Sql);
UserInfo info = null;
if(action_type.equals("login")) {
rs = preSta.executeQuery();
while(rs.next()){
info = new UserInfo();
info.setuser_id(rs.getInt("user_id"));
info.setUserName(rs.getString("username"));
info.setPassword(rs.getString("password"));
info.setPhone(rs.getString("phone"));
}
if(info != null){
session.setAttribute("password", password);
session.setAttribute("info", info);
String login_suc = "success.jsp";
response.sendRedirect(login_suc);
}
else{
String login_fail = "login.jsp";
session.setAttribute("errorMsg", "用户名或密码错误，登陆失败！");
response.sendRedirect(login_fail);
}
}
else if(action_type.equals("register")){
int count= preSta.executeUpdate();
if(count>0){
session.setAttribute("registerMsg", "注册成功！");
}
else{
session.setAttribute("registerMsg", "注册失败，请重试！");
}
response.sendRedirect("register.jsp");
}
} catch (Exception e) {
e.printStackTrace();
}
// 关闭连接
finally {
if(connection!=null){
try{
connection.close();
}catch(Exception e){}
}
if(preSta!=null){
try{
preSta.close();
}catch(Exception e){}
}
if(rs!=null){
try{
rs.close();
}catch(Exception e){}
}
}
}
}
MD5.Java:
MD5加密类，给password字段加密
package com.Account;
import java.security.MessageDigest;
public class Md5 {
public final String MD5(String s) {//MD5加密方法
char hexDigits[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
try {
byte[] btInput = s.getBytes();
// 获得MD5摘要算法的 MessageDigest 对象
MessageDigest mdInst = MessageDigest.getInstance("MD5");
// 使用指定的字节更新摘要
mdInst.update(btInput);
// 获得密文
byte[] md = mdInst.digest();
// 把密文转换成十六进制的字符串形式
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i++) {
byte byte0 = md[i];
str[k++] = hexDigits[byte0 >>> 4 & 0xf]; //>>>不带符号 右移 四位(位移处补0)
str[k++] = hexDigits[byte0 & 0xf];
}
return new String(str);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
ConnectionPool.java:
手动实现一个简单的数据库连接池，提升性能
package com.Account;
import java.sql.*;
import java.lang.reflect.*;
import java.util.*;
import java.io.*;
public class ConnectionPool {
private static LinkedList m_notUsedConnection = new LinkedList();
private static HashSet m_usedUsedConnection = new HashSet();
private static String m_url = "jdbc:mysql://localhost:3306/first_db";
private static String m_user = "root";
private static String m_password = "123456";
static final boolean DEBUG = true;
static private long m_lastClearClosedConnection = System.currentTimeMillis();
public static long CHECK_CLOSED_CONNECTION_TIME = 4 * 60 * 60 * 1000; // 4小时
private void ConnectionPool() {
}
static {
initDriver();
}
private static void initDriver() {
Driver driver = null;
// load mysql driver
try {
driver = (Driver) Class.forName("com.mysql.jdbc.Driver").newInstance();
installDriver(driver);
} catch (Exception e) {
}
}
public static void installDriver(Driver driver) {
try
{
DriverManager.registerDriver(driver);
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static synchronized Connection getConnection() {
clearClosedConnection();
while (m_notUsedConnection.size() > 0) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection
.removeFirst();
if (wrapper.connection.isClosed()) {
continue;
}
m_usedUsedConnection.add(wrapper);
if (DEBUG) {
wrapper.debugInfo = new Throwable(
"Connection initial statement");
}
return wrapper.connection;
} catch (Exception e) {
}
}
int newCount = getIncreasingConnectionCount();
LinkedList list = new LinkedList();
ConnectionWrapper wrapper = null;
for (int i = 0; i < newCount; i++) {
wrapper = getNewConnection();
if (wrapper != null) {
list.add(wrapper);
}
}
if (list.size() == 0) {
return null;
}
wrapper = (ConnectionWrapper) list.removeFirst();
m_usedUsedConnection.add(wrapper);
m_notUsedConnection.addAll(list);
list.clear();
return wrapper.connection;
}
private static ConnectionWrapper getNewConnection() {
try {
Connection con = DriverManager.getConnection(m_url, m_user,
m_password);
ConnectionWrapper wrapper = new ConnectionWrapper(con);
return wrapper;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
static synchronized void pushConnectionBackToPool(ConnectionWrapper con) {
boolean exist = m_usedUsedConnection.remove(con);
if (exist) {
m_notUsedConnection.addLast(con);
}
}
public static int close() {
int count = 0;
Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
try {
((ConnectionWrapper) iterator.next()).close();
count++;
} catch (Exception e) {
}
}
m_notUsedConnection.clear();
iterator = m_usedUsedConnection.iterator();
while (iterator.hasNext()) {
try {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
wrapper.close();
if (DEBUG) {
wrapper.debugInfo.printStackTrace();
}
count++;
} catch (Exception e) {
}
}
m_usedUsedConnection.clear();
return count;
}
private static void clearClosedConnection() {
long time = System.currentTimeMillis();
// sometimes user change system time,just return
if (time < m_lastClearClosedConnection) {
time = m_lastClearClosedConnection;
return;
}
// no need check very often
if (time - m_lastClearClosedConnection < CHECK_CLOSED_CONNECTION_TIME) {
return;
}
m_lastClearClosedConnection = time;
// begin check
Iterator iterator = m_notUsedConnection.iterator();
while (iterator.hasNext()) {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
try {
if (wrapper.connection.isClosed()) {
iterator.remove();
}
} catch (Exception e) {
iterator.remove();
if (DEBUG) {
System.out
.println("connection is closed, this connection initial StackTrace");
wrapper.debugInfo.printStackTrace();
}
}
}
// make connection pool size smaller if too big
int decrease = getDecreasingConnectionCount();
if (m_notUsedConnection.size() < decrease) {
return;
}
while (decrease-- > 0) {
ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection
.removeFirst();
try {
wrapper.connection.close();
} catch (Exception e) {
}
}
}
/**
* get increasing connection count, not just add 1 connection
*
* @return count
*/
public static int getIncreasingConnectionCount() {
int count = 1;
int current = getConnectionCount();
count = current / 4;
if (count < 1) {
count = 1;
}
return count;
}
/**
* get decreasing connection count, not just remove 1 connection
*
* @return count
*/
public static int getDecreasingConnectionCount() {
int count = 0;
int current = getConnectionCount();
if (current < 10) {
return 0;
}
return current / 3;
}
public synchronized static void printDebugMsg() {
printDebugMsg(System.out);
}
public synchronized static void printDebugMsg(PrintStream out) {
if (DEBUG == false) {
return;
}
StringBuffer msg = new StringBuffer();
msg.append("debug message in " + ConnectionPool.class.getName());
msg.append("
");
msg.append("total count is connection pool: " + getConnectionCount());
msg.append("
");
msg.append("not used connection count: " + getNotUsedConnectionCount());
msg.append("
");
msg.append("used connection, count: " + getUsedConnectionCount());
out.println(msg);
Iterator iterator = m_usedUsedConnection.iterator();
while (iterator.hasNext()) {
ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
wrapper.debugInfo.printStackTrace(out);
}
out.println();
}
public static synchronized int getNotUsedConnectionCount() {
return m_notUsedConnection.size();
}
public static synchronized int getUsedConnectionCount() {
return m_usedUsedConnection.size();
}
public static synchronized int getConnectionCount() {
return m_notUsedConnection.size() + m_usedUsedConnection.size();
}
public static String getUrl() {
return m_url;
}
public static void setUrl(String url) {
if (url == null) {
return;
}
m_url = url.trim();
}
public static String getUser() {
return m_user;
}
public static void setUser(String user) {
if (user == null) {
return;
}
m_user = user.trim();
}
public static String getPassword() {
return m_password;
}
public static void setPassword(String password) {
if (password == null) {
return;
}
m_password = password.trim();
}
}
class ConnectionWrapper implements InvocationHandler {
private final static String CLOSE_METHOD_NAME = "close";
public Connection connection = null;
private Connection m_originConnection = null;
public long lastAccessTime = System.currentTimeMillis();
Throwable debugInfo = new Throwable("Connection initial statement");
ConnectionWrapper(Connection con) {
this.connection = (Connection) Proxy.newProxyInstance(
con.getClass().getClassLoader(),
new Class[]{Connection.class}, this);
m_originConnection = con;
}
void close() throws SQLException {
m_originConnection.close();
}
public Object invoke(Object proxy, Method m, Object[] args)
throws Throwable {
Object obj = null;
if (CLOSE_METHOD_NAME.equals(m.getName())) {
ConnectionPool.pushConnectionBackToPool(this);
} else {
obj = m.invoke(m_originConnection, args);
}
lastAccessTime = System.currentTimeMillis();
return obj;
}
}
四.完成效果
首先user表是空的，然后在首页注册用户，然后查看数据库信息已经注册成功，再进行登陆，登陆成功后跳转到个人中心页面，修改密码手机等信息，完成后再次查看数据库
