servlet-复习02

目录

模拟登录

1.导入数据库和数据库连接池包

2.编写登录页面

3.创建配置文件和相关类

4.代码展示

问题与解决

---

模拟登录

1.导入数据库和数据库连接池包

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>1.4</version>
        </dependency>

2.编写登录页面

 <form action="/hello" method="post">
    账号：<input type="text" name="username"><br>
    密码：<input type="text" name="password"><br>
    <input type="submit" value="登录">
  </form>

3.创建配置文件和相关类

dp.url=jdbc:mysql://localhost:3306/newdb3
dp.driver=com.mysql.jdbc.Driver
dp.password=root
dp.userName=root
dp.initnum=3
dp.maxNum=5

4.代码展示

HelloServlet类

public class HelloServlet extends HttpServlet
{
    @Override
    public void service(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        System.out.println("请求收到了");
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        //            resp.getWriter().println("<h1>请求收到了</h1>");
        String name=req.getParameter("username");
        String password=req.getParameter("password");
        UserService service=new UserService();
        User user=service.getOneBynameAndpassword(name,password);
        if(user!=null)
        {
            resp.getWriter().println("<h1>登陆成功</h1>");
        }
        resp.getWriter().print("<h1>用户名或者密码错误</h1>");



    }
}

DBUtil类

/*

提供数据库链接的


 */
public class DBUtil {
    private static String userName;
    private static String password;
    private static String driver;
    private static String url;
    private static int initNum;
    private static int maxNum;
    private static BasicDataSource bs;
    static{
        bs=new BasicDataSource();
        //读取配置文件
        Properties p=new Properties();
        InputStream is= DBUtil.class.getClassLoader().getResourceAsStream("dp.properties");


        try {
            p.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
          url=p.getProperty("dp.url");
         driver=p.getProperty("dp.driver");
         userName=p.getProperty("dp.userName");
         password=p.getProperty("dp.password");
         initNum=Integer.parseInt(p.getProperty("dp.initnum"));
         maxNum=Integer.parseInt(p.getProperty("dp.maxNum"));
         bs.setDriverClassName(driver);
         bs.setUrl(url);
         bs.setUsername(userName);
         bs.setPassword(password);
        //设置初始连接数量
         bs.setInitialSize(3);
        //设置最大连接数量
         bs.setMaxActive(5);
    }



    public  static Connection getConnection(){
        Connection conn=null;
        try {
            //通过数据库连接池来进行链接获取链接对象
            conn=bs.getConnection();



//            Class.forName(driver);
//           conn= DriverManager.
//                    getConnection(url,userName,password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //        2.获取链接

        return conn;
    }


    public static void close(Connection conn){
        try {
            if(conn!=null) {
                conn.close();
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

    }

}

Service类

public class UserService {
    UserDao dao=new UserDao();
    public User getOneBynameAndpassword(String name, String password) {

        return  dao.getOneBynameAndpassword(name,password);
    }
}

 UserDao类

public class UserDao {
    public User getOneBynameAndpassword(String name, String password) {
        Connection connection= DBUtil.getConnection();
        String sql="select *from t1 where username=? and password=?";
        User user1=null;
        try {
            PreparedStatement preparedStatement=connection.prepareStatement(sql);
           preparedStatement.setString(1,name);
           preparedStatement.setString(2,password);
            ResultSet rs=preparedStatement.executeQuery();
            while(rs.next())
            {
                user1=new User();
                String username=rs.getString("username");
                System.out.println(rs.getString("username"));
                String pass=rs.getString("password");
                System.out.println(rs.getString("password"));
                user1.setUsername(username);
                user1.setPassword(pass);
            }


        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
return user1;
    }
}

 User类

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


    public User() {
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public int getId() {
        return id;
    }

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

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

}

问题与解决

运行结果如图

就是说我的jar包没有加载进来，明明依赖没有爆红奇怪

 然后手动导入到web下面

然后又出现l错误，发现连接池那个类初始化错误，配置文件名字写错了

来了，最坑爹的来了，

setString（第几个问号，要传入的值）

executeQuery()提交

getString("数据库属性")