java -Web-tomcat页面登录密码验证案例

Web登录检验案例

1.准备工作：

创建web项目，工具为idea，写好html登录页面，引入数据库连接池以及JDBCtemplate（spring）所需的jar包，把pro文件写好加入到src目录下，作为数据库连接池内部注册驱动连接数据库等操作使用。

2.准备mysql数据库：

CREATE TABLE USER(
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(30) UNIQUE NOT NULL,
	PASSWORD VARCHAR(30) NOT NULL
);

3.写好src下的java类：

分别需要不同的模块，一个是用户封装类user，一个是登录逻辑检验的类dao，一个是jdbcutils类，封装好连接获取，最重要的是servlet类，一个用来获取消息，并且设置好request域的资源共享，用于反馈到网页上登录成功或者失败的消息。

/**
 * 获取数据库信息并且判断
 */
public class Login {
    private JdbcTemplate template = new JdbcTemplate(JDBC_utils.getDataSource());

    public User login(User user) {
        String sql = "select * from user where username = ? and password = ?";
        User user1 = template.queryForObject(sql,
                new BeanPropertyRowMapper<>(User.class),
                user.getUsername(), user.getPassword()
        );
        return user1;
    }
}

package cn.domain;

public class User {
    private String username;
    private String password;
    private int id;

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", id=" + id +
                '}';
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
}

public class JDBC_utils {
    private static DataSource dataSource;

    static {
        try {
            Properties properties = new Properties();
            InputStream resourceAsStream = JDBC_utils.class.getClassLoader().getResourceAsStream("druid.propertis");
            properties.load(resourceAsStream);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static DataSource getDataSource(){
        return dataSource;
    }


    public static Connection getConnection() throws SQLException {
            return dataSource.getConnection();
    }
}

public class LoginServlet extends HttpServlet {


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf-8");
        //2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);

        //4.调用UserDao的login方法
        Login dao = new Login();
        User user = dao.login(loginUser);

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/fail").forward(req,resp);
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/success").forward(req,resp);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

@WebServlet("/success")
public class Success_Servlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write("ok");
    }

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

4.使用Beanutils简化request接收到的数据的封装：

 Map<String, String[]> parameterMap = req.getParameterMap();
        User loginUser = new User();

        try {
            BeanUtils.populate(loginUser, parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

参数分别为map和User自定义对象。

5.罪大恶极的问题！ httpHTTP 500 Internal server error，终于解决

问题是Caused by: java.lang.NoClassDefFoundError: org/springframework/dao/DataAccessException，几经周转一直写注解test，但是一直找不出问题，网上搜的问题又都不一样，排查了web-inf 下的lib名称都没错，
最后直接把lib删除了重新导入，然后重新导入，最重要的一步在结构目录里面
把lib添加进去！！！！