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第五章 Cookie 和 Session

1.蛋糕商城

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public class PurchaseServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String id = (String) req.getAttribute("id");
        if(id==null){
            resp.sendRedirect("/ListBookServlet");
            return;
        }

        Book book = BookDB.getBook(id);
        HttpSession session = req.getSession();
        List<Book>cart = (List)session.getAttribute("cart");

        if(cart == null){
            cart = new ArrayList<Book>();
            session.setAttribute("cart");
        }
        cart.add(book);

        Cookie cookie = new Cookie("JSESSIONID",session.getID());
        cookie.setMaxAge(60*30);
        cookie.setPath("/chapter06");
        resp.addCookie(cookie);

        resp.sendRedirect("BookServlet");
    }
}

2.显示上次访问时间

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@WebServlet(name="lastAccessServlet",urlPatterns="/lastAccessServlet")
public class LastAccessServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");

        String lastAccessTime = null;
        Cookie[] cookies = req.getCookies();

        for(Cookie cookie : cookies){
            if("lastAccess".equals(cookie.getName())){
                lastAccessTime = cookie.getValue();
                break;
            }
            resp.getWriter().println(cookie.getName());
        }

        if(lastAccessTime == null){
            resp.getWriter().print("您是首次访问！");
        }else{
            resp.getWriter().print("您上次访问的时间是：" + lastAccessTime);
        }

        Cookie cookie = new Cookie("lastAccess", new Date().toString());
        cookie.setMaxAge(60*60);
        cookie.setPath("/School_war_exploded");
        resp.addCookie(cookie);
    }
}

第六章 JSP

1.显示时间

time.jsp

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<%@ page contentType ="text/html;charset=utf-8" %>
<%@ page import = "java.util.Date" %>
<%@ page import = "java.text.SimpleDateFormat" %>

欢迎访问 ， 现在的时间是：
<%
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd HH:mm:ss");
    String str = sdf.format(new Date());
%>

<%= str%>

time_main.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<jsp:include page = "time.jsp" />

2.写两个jsp，要求显示b，等待5s显示a

a.jsp

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<%@ page contentType="text/html;charset=utf-8" %>

<% Thread.sleep(5000); %>
a.jsp中的中文

b.jsp

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<%@ page contentType="text/html;charset=utf-8" %>

b.jsp的中文
<jsp:include page="a.jsp" flush="true" />

第八章

UserBean

注意属性不能大写！

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package Entity;

public class User {
    private String username = "zhangsan";
    private int age = 20;
    private String sex = "nan";

    public int getAge() {
        return age;
    }
    public String getUsername(){
        return username;
    }
    public String getSex() {
        return sex;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public void setUsername(String username) {
        username = username;
    }
}

add.jsp

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<%--
  Created by IntelliJ IDEA.
  User: lenovo
  Date: 2024-01-02
  Time: 22:03
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <form action="info.jsp" method="get">
    姓名：<input type="text" name="username"> <br>
    年龄：<input type="text" name="age"> <br>
    性别：<input type="text" name="sex"> <br>
    <input type="submit" value="添加">
  </form>
</body>
</html>

info.jsp

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<%@ page contentType="text/html;charset=utf-8" %>

<html>
<head>
    <title>title</title>
</head>

<body>
    <% request.setCharacterEncoding("utf-8"); %>
    <jsp:useBean id="user" class="Entity.User" scope="page">
        // 通过表单提交赋值
        <jsp:setProperty name="user" property="*"></jsp:setProperty>
    </jsp:useBean>
    
    // 通过直接赋值
    <jsp:setProperty name="user" property="username" value="skyang" />
    <jsp:setProperty name="user" property="age" value="111" />
    <jsp:setProperty name="user" property="sex" value="男" />

    <table>
        <tr>
            <td>姓名： <jsp:getProperty property="username" name="user"/> </td>
        </tr>
        <tr>
            <td> 年龄： <jsp:getProperty property="age" name="user" /> </td>
        </tr>
        <tr>
            <td> 性别： <jsp:getProperty property="sex" name="user"/></td>
        </tr>
    </table>
</body>

</html>

第十章

1.基本步骤

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public static void main(String[] args) throws SQLException{
        // 1.加载数据库驱动
        DriverManager.registerDriver(new com.example.mysql.jdbc.Driver());
        
        // 2.通过DriverManager获取数据库链接
        String url = "jdbc:mysql://localhost:3306/jdbc";
        String username = "skyang";
        String password = "skyang";
        Connection conn = DriverManager.getConnection(url,username,password);
        
        // 3.通过Connection对象获取Statement对象
        Statement stmt = conn.createStatement();
        
        // 4.使用Statement独享执行SQL语句
        String sql = "select * from users";
        ResultSet rs = stmt.executeQuery(sql);
        
        // 5.操作ResultSet结果集
        while(rs.next()){
            String name = rs.getString("name");
            String word = rs.getString("password");
        }
        
        // 6.回收数据库资源
        rs.close();
        stmt.close();
        conn.close();
    }

2.PrepareStatement

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conn = JDBCUtils.getConnection();
String sql = "select password from users where username= ?";
ps = conn.prepareStatement(sql);

ps.setString(1, user.getUsername());
rs = ps.executeQuery();

3.JDBCUtils

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package Utils;

import java.sql.*;

public class JDBCUtils {
    public static Connection getConnection() throws SQLException,ClassNotFoundException{
        Class.forName("com.mysql.cj.jdbc.Driver");
        String url = "jdbc:mysql://127.0.0.1:3306/bloguser?serverTimezone=UTC&useUnicode=true&characterEncoding=utf8";
        String username = "root";
        String password = "skyang9";

        Connection conn = DriverManager.getConnection(url,username,password);
        return conn;
    }

    public static void release(PreparedStatement stmt , Connection conn){
        if(stmt != null){
            try{
                stmt.close();
            }catch(SQLException e){
                e.printStackTrace();
            }
        }
        if(conn != null){
            try{
                conn.close();
            }catch(SQLException e){
                e.printStackTrace();
            }
        }
    }

    public static void release(ResultSet rs , PreparedStatement stmt , Connection conn){
        if(rs != null){
            try{
                rs.close();
            }catch(SQLException e){
                e.printStackTrace();
            }
        }
        release(stmt,conn);
    }
}

UserDAO部分

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public static String Find(User user){
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try{
        conn = JDBCUtils.getConnection();
        String sql = "select password from users where username= ?";
        ps = conn.prepareStatement(sql);

        ps.setString(1, user.getUsername());
        rs = ps.executeQuery();

        String SQLpassword;
        while(rs.next()){
            SQLpassword = rs.getString("password");
            return SQLpassword;
        }
    }catch(Exception e){
        e.printStackTrace();
    }finally{
        JDBCUtils.release(rs,ps,conn);
    }
    return null;
}