web项目 maven下 使用servlet调用 mysql数据库

在登录界面的基础下，需要先配置 mysql 数据库，然后修改 Verify.java 就可以了，登陆界面项目：点击打开链接

首先建立简单的数据库和表：

CREATE TABLE users (
userId INT PRIMARY KEY,
username VARCHAR(20),
passwd VARCHAR(20),
grade INT);

INSERT INTO `users` (`userId`, `username`, `passwd`, `grade`) VALUES('1','admin','123','1');
INSERT INTO `users` (`userId`, `username`, `passwd`, `grade`) VALUES('2','hou','123','2');
INSERT INTO `users` (`userId`, `username`, `passwd`, `grade`) VALUES('3','test','123','3');

然后通过登录界面，调用数据库判断，如果是数据库中的用户名，就在welcome页面输出用户名和密码。

package com.busymonkey;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;

public class Verify extends HttpServlet {
private static final long serialVersionUID = 1L;

public Verify() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Connection ct = null;
Statement sm = null;
ResultSet rs = null;
try {
String u=request.getParameter("username");
String p=request.getParameter("passwd");

//数据库连接
Class.forName("com.mysql.jdbc.Driver");
//得到连接
ct = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/db_hou", "root", "123456");
//创建Statement
sm = ct.createStatement();
rs = sm.executeQuery("select * from users where username='"+u
+"' and passwd='"+p+"'");

if (rs.next()) {
HttpSession hs = request.getSession(true);
hs.setMaxInactiveInterval(20);
hs.setAttribute("pass", "ok");
response.sendRedirect("welcome?uname=" + u + "&upass=" + p);
}
else {
response.sendRedirect("login");
}
}
catch (Exception ex) {
ex.printStackTrace();
}finally{
try {
if (rs!=null) rs.close();
if (sm!=null) sm.close();
if (ct!=null) ct.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
}
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}

}

然后maven pom文件包括依赖

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.31</version>
</dependency>

这里注意一个问题，通常情况下maven自动下载的依赖会放到项目的 target 目录的项目文件夹下，但是在 tomcat 服务器启动是在 tomcat 安装目录下的 webapps 目录下，而在maven项目 install 的时候，是把 src 目录下的 WEB-INI 文件同步到 tomcat 安装文件夹下的 webapps 目录中，所以如果 tomcat 的 webapps 目录下，相对应启动的项目中没有同步lib依赖，那就把maven 项目中target中的lib依赖拷贝到src文件夹的main文件夹中的lib中，再进行maven
install。这样就可以同步依赖文件了。

对于sql注入漏洞，修改的verify.java 代码如下：

package com.busymonkey;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;

public class Verify extends HttpServlet {
private static final long serialVersionUID = 1L;

public Verify() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Connection ct = null;
Statement sm = null;
ResultSet rs = null;
try {
String u=request.getParameter("username");
String p=request.getParameter("passwd");

//数据库连接
Class.forName("com.mysql.jdbc.Driver");
//得到连接
ct = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/db_hou", "root", "123456");
//创建Statement
sm = ct.createStatement();
rs = sm.executeQuery("select * from users where username='"+u+"' and passwd='"+p+"'");

if (rs.next()) {//next能进来说明用户是存在的
String dbPasswd = rs.getString("passwd");
if (dbPasswd.equals(p)) {
HttpSession hs = request.getSession(true);
hs.setMaxInactiveInterval(20);
hs.setAttribute("pass", "ok");
response.sendRedirect("welcome?uname=" + u + "&upass=" + p);
}
else
{
response.sendRedirect("login");
}
}
else {
response.sendRedirect("login");
}
}
catch (Exception ex) {
ex.printStackTrace();
}finally{
try {
if (rs!=null) rs.close();
if (sm!=null) sm.close();
if (ct!=null) ct.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
}
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}

}

如果要用servlet显示图片，则在wel页面加入一句话即可，然后图片放到 tomcat下webapps下的项目文件夹中的WEB-INF文件夹下，新建一个imgs的文件夹，将图片放在里面即可：

package com.busymonkey;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.*;

public class WelCome extends HttpServlet {
private static final long serialVersionUID = 1L;

public WelCome() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession hs = request.getSession(true);
String val = (String) hs.getAttribute("pass");//非法登陆返回空
if ( val == null )
{
try {
response.sendRedirect("login");
}
catch (Exception ex) {
ex.printStackTrace();
}
}
String u = request.getParameter("uname");
String p = request.getParameter("upass");
try {
PrintWriter pw = response.getWriter();
pw.println("<img src=./imgs/1.GIF ><br>");
pw.println("Welcome!!!! " + u + " pass=" + p);
}
catch (Exception ex) {
ex.printStackTrace();
}
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}

}