摘要：新建一个项目选择自己的文件勾选项目构造如下设置项目配置快捷键选择配置红色框选择时，运行成功会会自动运行下方的链接测试运行出现如下便创建成功编写第一个代码，测试环境是否设置成功第一个设置响应内容类型实际的逻辑是

Flies --> new --> project-->ProjectSDK选择自己的JDK文件-->勾选Web Appliction -->Next

File --> Project Structure (快捷键：Ctrl + Shift + Alt + S) --> 选择Module ：

红色框选择时，运行成功会会自动运行下方的URL链接

出现如下便创建成功

@WebServlet("/firstServlet")
public class test extends HttpServlet {

    private String message;

    @Override
    public void init() throws ServletException {
        message = "第一个servlet";
    }

    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
            throws ServletException, IOException
    {
        // 设置响应内容类型
//        response.setContentType("text/html");
        response.setHeader("Content-type","text/html;charset=UTF-8");

        // 实际的逻辑是在这里
        PrintWriter out = response.getWriter();
        out.println("
" + message + "
");
    }

    public void destroy()
    {
        // 什么也不做
    }
}

注解@WebServlet是设置该类的URL，也可以在web.xml里设置，如下：

    test//设置该servlet的名字，可以随便定义
    test.test//对应的java的文件（包名.类名）



    test//上面定义的名字
    /HelloWorld//自己定义URL

运行Tomcat,打开浏览器输入http://localhost:8080/firstServlet或者http://localhost:8080/HelloWorld结果：

资源：mysql-connector-java-5.1.39-bin.jar
链接：http://note.youdao.com/notesh...

public class connectionUtil {
    private static String  driver;
    private static String  url;
    private static String  username;
    private static String password;

    static {
        try {

            //获取配置文件的信息
            driver = "com.mysql.jdbc.Driver";
            url = "jdbc:mysql://localhost:3306/test";
            username = "root";
//            password = "admin";
            password = "touwen";

            //加载驱动类
            Class.forName(driver);

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

    }

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,username,password);
    }

    public static void release(Connection connection, Statement statement, ResultSet resultSet) {

        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

注册逻辑

@WebServlet("/registered")
public class registered extends HttpServlet {


    public registered(){
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String username = new String(request.getParameter("username").getBytes("ISO8859-1"),"UTF-8");
        String password1 = request.getParameter("password1");
        String password2 = request.getParameter("password2");
        if(password1 == null || password2 == null){
            System.out.println("请输入密码");
        }
        if(password1.equals(password2)){
            Connection conn = null;
            ResultSet rs = null;
            PreparedStatement ptst = null;
            try{
                conn = connectionUtil.getConnection();
                String sql = "SELECT username FROM user";
                ptst = conn.prepareStatement(sql);
                rs = ptst.executeQuery();
                while (rs.next()) {
                    if(username.equals(rs.getString("username"))){
                        System.out.println("用户名已存在");
                        return;
                    }
                }
                String ins = "insert into user(username,password) values (?,?)";
                ptst = conn.prepareStatement(ins);
                ptst.setString(1,username);
                ptst.setString(2,password1);
                int i = ptst.executeUpdate();
                if(i==1) {
                    System.out.println("注册成功");
                }else {
                    System.out.println("注册失败");
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }finally {
                connectionUtil.release(conn,ptst,rs);
            }
        }else {
            System.out.println("两次密码不一致");
        }

    }

    // 处理 POST 方法请求的方法
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

登录逻辑

@WebServlet("/login")
public class login extends HttpServlet {

    public login(){
        super();
    }

    @Override
    // 处理 POST 方法请求的方法
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        Connection conn = null;
        PreparedStatement ptst = null;
        ResultSet rs = null;

        String username = new String(request.getParameter("username").getBytes("ISO8859-1"),"UTF-8");
        String password = request.getParameter("password");
        if(username == null || password == null){
            System.out.println("请输入账号或者密码");
        }
        try {
            conn = connectionUtil.getConnection();
            String sql = "SELECT * FROM user where username = ?";
            ptst = conn.prepareStatement(sql);
            ptst.setString(1,username);
            rs = ptst.executeQuery();
            while (rs.next()){
                if(password.equals(rs.getString("password"))){
                    System.out.println("登陆成功");
                }else {
                    System.out.println("账号密码不正确");
                }
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            connectionUtil.release(conn,ptst,rs);
        }
    }
}

如果一直连接不上数据库时，需要在java的运行环境外部也需要导入JDBC的包，路径是安装的java文件夹下的jrelibext