JAVA 入门学习之路-注册登录案例。

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新建项目，结构如下：

项目结构

对于新建的项目，需要做一些基本配置，如果已经配置，略过，不会配置的详见：
JAVA WEB 学习笔记 Idea下常用配置-Hello Servlet。

新建数据库连接工具类：

/** * 数据库连接工具类 * Created by Chao on 2016/12/3. */public class DBUtils {    private static String driverClass;    private static String url;    private static String username;    private static String password;    static {        ResourceBundle bundle = ResourceBundle.getBundle("dbinfo");//加载文件        driverClass = bundle.getString("driverClass");        url = bundle.getString("url");        username = bundle.getString("username");        password = bundle.getString("password");        try {            Class.forName(driverClass);        } catch (ClassNotFoundException e) {            e.printStackTrace();        }    }    //得到连接    public static Connection getConnection() throws Exception {        return DriverManager.getConnection(url, username, password);    }    //关闭资源    public static void closeAll(ResultSet rs, Statement stm, Connection conn) {        if (rs != null) {            try {                rs.close();            } catch (SQLException e) {                e.printStackTrace();            }            rs = null;        }        if (stm != null) {            try {                stm.close();            } catch (SQLException e) {                e.printStackTrace();            }            stm = null;        }        if (conn != null) {            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }            conn = null;        }    }}

上面数据库连接信息，写在了配置文件里，附上文件：

连接配置

编写一个登陆和一个注册的jsp页面：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>用户注册</title></head><body><h2 style="color: red">新用户注册</h2>${error}<form action="/register" method="post">    账号:<input type="text" value="zhangzhichao" name="name"><br/>    密码:<input type="password" value="chaochao" name="pwd"><br/>    手机:<input type="text" value="13500000000" name="phone"><br/>    <input type="submit" value="注册"><br/></form></body></html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>用户登录</title></head><body><h2 style="color: red">登陆</h2>${error}<form action="/login" method="post">    账号:<input type="text" value="zhangzhichao" name="name"><br/>    密码:<input type="password" value="chaochao" name="pwd"><br/>    <input type="submit" value="登陆"><br/></form></body></html>

到这里页面编写已经完成，只需完成响应页面即可。

对了，这里先设计数据库和表，与上面的连接配置中的数据库名和表名一致。

数据库结构

下面编写在bean包名下的实体类，属性与数据库表对应：

/** * 用户信息实体类 * Created by Chao on 2016/12/11. */public class User implements Serializable {    private int id;    private String name;    private String pwd;    private String phone;    private Date date;    public User() {    //由于为了简便，我这里直接取当前时间作为创建用户时间，先进行赋值。        date = new Date();    }    public boolean validate() {        return true;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getPwd() {        return pwd;    }    public void setPwd(String pwd) {        this.pwd = pwd;    }    public String getPhone() {        return phone;    }    public void setPhone(String phone) {        this.phone = phone;    }    public Date getDate() {        return date;    }    public void setDate(Date date) {        this.date = date;    }}

在包名dao目录下新建接口：

/** * Created by Chao on 2016/12/11. */public interface UserDao {    /**     * 添加用户信息     *     * @param user     * @throws Exception     */    public void addUser(User user) throws Exception;    /**     * 根据用户名和密码查找用户信息     *     * @param user     * @return     * @throws Exception     */    public User findUser(User user) throws Exception;    /**     * 根据用户名查找用户是否存在     * @param name     * @return     */    public boolean findUserByName(String name);}

接下来daoimpl包名下新建类实现功能：

/** * Created by Chao on 2016/12/11. */public class UserDaoImpl implements UserDao {    /**     * 添加用户     *     * @param user     */    @Override    public void addUser(User user) throws Exception {        Connection conn = null;        PreparedStatement ps = null;        try {            conn = DBUtils.getConnection();            ps = conn.prepareStatement("INSERT INTO users(name,pwd,phone,DATE) VALUES(?,?,?,?)");            ps.setString(1, user.getName());            ps.setString(2, user.getPwd());            ps.setString(3, user.getPhone());            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");            String date = sdf.format(user.getDate());            ps.setString(4, date);            int i = ps.executeUpdate();        } catch (Exception e) {            e.printStackTrace();            throw new RuntimeException("添加失败！");        } finally {            DBUtils.closeAll(null, ps, conn);        }    }    /**     * 查询用户     *     * @param user     * @return     * @throws Exception     */    public User findUser(User user) throws Exception {        Connection conn = null;        PreparedStatement ps = null;        ResultSet rs = null;        User u = null;        try {            conn = DBUtils.getConnection();            ps = conn.prepareStatement("select * from users where name=? and pwd=?");            ps.setString(1, user.getName());            ps.setString(2, user.getPwd());            rs = ps.executeQuery();            if (rs.next()) {                u = new User();                u.setId(rs.getInt(1));                u.setName(rs.getString(2));                u.setPwd(rs.getString(3));                u.setPhone(rs.getString(4));                u.setDate(rs.getDate(5));            }        } catch (Exception e) {            e.printStackTrace();        } finally {            DBUtils.closeAll(rs, ps, conn);        }        return u;    }    public boolean findUserByName(String name) {        Connection conn = null;        PreparedStatement ps = null;        ResultSet rs = null;        try {            conn = DBUtils.getConnection();            ps = conn.prepareStatement("select * from users where name=?");            ps.setString(1, name);            rs = ps.executeQuery();            if (rs.next()) {                return true;            }        } catch (Exception e) {            e.printStackTrace();        } finally {            DBUtils.closeAll(rs, ps, conn);        }        return false;    }}

包名servlet包名下编写接口：

/** * Created by Chao on 2016/12/11. */public interface UserServlet {    /**     * 添加用户信息     *     * @param user     * @throws Exception     */    public void register(User user) throws Exception;    /**     * 根据用户名和密码查找用户信息     *     * @param user     * @return     */    public User login(User user) throws UsersException;    /**     * 根据用户名查找用户是否存在     * @return     * @throws UserExistException     */    public boolean findUserByName(String name) throws UserExistException;}

包名servletimpl实现接口：

public class UserServiceImpl implements UserServlet {    UserDao userDao = new UserDaoImpl();    public void register(User user) throws Exception {        userDao.addUser(user);    }    public User login(User user) {        User u = null;        try {            u = userDao.findUser(user);        } catch (Exception e) {            e.printStackTrace();            //写入日志        }        return u;    }    public boolean findUserByName(String name) throws UserExistException {        boolean b = userDao.findUserByName(name);        if(b){            throw new UserExistException("用户名已存在");        }        return b;    }}

包名webservlet下编写登陆和注册响应服务：

/** * Created by Chao on 2016/12/11. */public class LoginServlet extends BaseHttpServlet {    @Override    public void httpAll(HttpServletRequest request, HttpServletResponse resp) throws IOException, ServletException {        super.httpAll(request, resp);        User user = new User();        try {            BeanUtils.populate(user, request.getParameterMap());        } catch (Exception e1) {            e1.printStackTrace();        }        UserServlet us = new UserServiceImpl();        User u;        try {            u = us.login(user);            //分发转向            if (u != null) {                request.getSession().setAttribute("u", user);//如果登录成功，就把user对象放到session对象 中                request.getRequestDispatcher("/index.jsp").forward(request, resp);            } else {                request.setAttribute("error", "登陆失败，请检查账号密码是否正确");                request.getRequestDispatcher("/login.jsp").forward(request, resp);            }        } catch (UsersException e) {            e.printStackTrace();        }    }}

/** * Created by Chao on 2016/12/11. */public class RegServlet extends BaseHttpServlet {    @Override    public void httpAll(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {        super.httpAll(request, response);// 获取表单数据        // 验证操作        User uf = new User();        try {            BeanUtils.populate(uf, request.getParameterMap());        } catch (Exception e1) {            e1.printStackTrace();        }        if (!uf.validate()) {// 如果map中不为空，说明有错误信息            request.setAttribute("uf", uf);            request.getRequestDispatcher("/register.jsp").forward(request, response);            return;        }        User user = new User();        try {            /*             * ConvertUtils.register(new Converter() {//注册一个日期转换器             *             * public Object convert(Class type, Object value) { Date date1 =             * null; if(value instanceof String){ String date = (String) value;             * SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); try {             * date1 = sdf.parse(date); } catch (ParseException e) {             * e.printStackTrace(); } } return date1; } }, Date.class);             */            ConvertUtils.register(new DateLocaleConverter(), Date.class);            BeanUtils.populate(user, request.getParameterMap());            // 调用业务逻辑            UserServlet us = new UserServiceImpl();            //查看用户名是否已被注册            us.findUserByName(user.getName());            us.register(user);        } catch (UserExistException e) {            request.setAttribute("error", "用户名已存在");            request.getRequestDispatcher("/register.jsp").forward(request, response);        } catch (Exception e) {            e.printStackTrace();        }        // 分发转向        response.getWriter().write("注册成功！1秒跳转到主页");        response.setHeader("refresh", "1;url=" + request.getContextPath()                + "/login.jsp");    }}

以上，项目已经可以运行，需要注意上面的异常，可以改成Exception，我为了测试继承Exception写了测试用的异常，请忽略。
整个项目结构如上：

上面有几个jar包，这里解释一下，到处都可以下载，我用这个版本比较老，上面3个jar包功能是：数据库连接jar包和bean映射jar包。

最后我们jsp页面配置的响应服务记得别忘了在xml里配置一下哦web.xml：

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"         version="3.1">    <servlet>        <servlet-name>login</servlet-name>        <servlet-class>com.chao.webservlet.LoginServlet</servlet-class>    </servlet>    <servlet>        <servlet-name>register</servlet-name>        <servlet-class>com.chao.webservlet.RegServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>login</servlet-name>        <url-pattern>/login</url-pattern>    </servlet-mapping>    <servlet-mapping>        <servlet-name>register</servlet-name>        <url-pattern>/register</url-pattern>    </servlet-mapping></web-app>

对了，新建项目的index.jsp文件内容小改了一下，用于显示登陆成功用户名等操作，附上源码：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>主页</title></head><body>欢迎您${u.name}</body></html>

所有代码基本都贴出来了，为防有遗漏，稍后附上Demo地址。

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