2021.3.6--JavaEE2 JSP 笔记 - 《Java学习笔记---武伟》

《学习内容》：

//========学习内容=========
JSP内置对象（4）
JSP内置对象（5）请求与会话的区别
JSP内置对象（6）其余的内置对象
JSP指令标签

《知识点—笔记》
//=========================
response.sendRedirect(“地址”);这个方法用来重定向但是并没有带走request和response对象所以他是一次新的请求
response.addCookie(new Cookie(“username”,uname));可以添加一个cookie，是在客户端（浏览器）发起
response.addCookie(new Cookie(“password”,password));可以添加一个cookie，是在客户端（浏览器）发起
HttpSession session = request.getSession() 来获取一次请求的session
session.setAttribute(“key”,value) 来往会话中添加一个键值对
Object obj = session.getAttribute(“key”) 来获取会话中的一个值
Enumration em = session.getAttributeNames(); 来获取session会话中的全部的key
Object obj = application.getAttribute(); 获取全局上下文中的value
Enumration em =application.getAttributeNames();获取上下文中的全部key
String value = application.getInitParameter();获取init携带的参数
boolean flag = application.setInitParameter()添加一个init携带的参数

《代码内容》：

主要思路—->通过代码来演练转发和重定向一次请求和新请求的区别
通过代码演练Session一次会话的过程在浏览器没有关闭都属于一次会话
更新之前的Atm系统，把中间带参数转发走，改为登录成功后，设置一个session.setAttribute(“key”,value)
在后面需要拿的时候只要在当前会话中就可以直接用session.getAttribute(“key”)来回去到当前的uname值

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <body>
        <form action="login" method="post">
          username:<input type="text" name="username" value=""><br>
          password:<input type="password" name="password" value=""><br>
          <input type="submit" value="login">
        </form>
  </body>
</html>

welcome.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
    <%
        String uname = request.getParameter("username");
        String password = request.getParameter("password");
    %>
<body>
        我是welcome.jsp<br>
        <%=uname%><br>
        <%=password%><br>
</body>
</html>

loginController

package controller;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginController extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        request.setCharacterEncoding("UTF-8");
        String uname = request.getParameter("username");
        String password = request.getParameter("password");
        //请求转发
        request.getRequestDispatcher("welcome.jsp").forward(request,response);
    }
}

输出结果

LoginController 重定向代码

package controller;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginController extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        request.setCharacterEncoding("UTF-8");
        String uname = request.getParameter("username");
        String password = request.getParameter("password");
        response.sendRedirect("welcome.jsp");
    }
}

输出结果

ATM优化会话代码

package controller;
import service.AtmService;
import util.MySpring;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
public class LoginController extends HttpServlet {
    private static AtmService atmSevice = MySpring.getBean("service.AtmService");
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String uname = request.getParameter("uname");
        String upassword = request.getParameter("upassword");
        //调用业务层的登录业务方法
        String loginResult = atmSevice.login(uname,upassword);
        if (loginResult.equals("登录成功")){
            //如果登录成功的话 设置一个session来把这个请求的参数值给添加到会话中去
            HttpSession session = request.getSession();
            session.setAttribute("uname",uname);
            //告知请求转发的地址  并真实的转发出去
            request.getRequestDispatcher("welcome.jsp").forward(request,response);
        }else {
            request.getRequestDispatcher("index.html").forward(request,response);
        }
    }
}
package controller;
import service.AtmService;
import util.MySpring;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class DoCunController extends HttpServlet {
    private AtmService atmService = MySpring.getBean("service.AtmService");
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        HttpSession session = request.getSession();
        String uname = (String)session.getAttribute("uname");
        String cunbal = request.getParameter("ubal");
        atmService.cun(uname,Float.parseFloat(cunbal));
    }
}
package controller;
import service.AtmService;
import util.MySpring;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.swing.*;
import java.io.IOException;
public class DoQuController extends HttpServlet {
    private static AtmService atmService = MySpring.getBean("service.AtmService");
    public void service(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
        request.setCharacterEncoding("UTF-8");
        HttpSession session = request.getSession();
        String uname = (String) session.getAttribute("uname");
        String bal = request.getParameter("ubal");
        atmService.qu(uname,Float.parseFloat(bal));
    }
}
package controller;
import com.mysql.cj.protocol.a.MysqlBinaryValueDecoder;
import service.AtmService;
import util.MySpring;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class DoZhuanController extends HttpServlet {
    private static AtmService atmService = MySpring.getBean("service.AtmService");
    @Override
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        HttpSession session = request.getSession();
        String uname = (String) session.getAttribute("uname");
        String zhuanbal = request.getParameter("zhuanbal");
        String youname = request.getParameter("youname");
        //调用业务层转账方法
        atmService.zhuan(uname,youname,Float.parseFloat(zhuanbal));
    }
}
package controller;
import service.AtmService;
import util.MySpring;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
public class QueryController extends HttpServlet{
    private static AtmService atmService = MySpring.getBean("service.AtmService");
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        HttpSession session = request.getSession();
        String uname = (String)session.getAttribute("uname");
        System.out.println(uname);
        //调用业务层获取余额
        Float ubal = atmService.query(uname);
        System.out.println(ubal);
        //往底层的参数集合中添加一个key--value
        request.setAttribute("ubal",ubal.toString());
       //告知路径并转发走
        request.getRequestDispatcher("query.jsp").forward(request,response);
    }
}
<html>
<head>
    <meta charset="UTF-8">
</head>
<body>
    <form action="login" method="post">
        账号<input type="text" name="uname" value=""><br>
        密码<input type="password" name="upassword" value=""><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
尊敬的<%=session.getAttribute("uname")%>您的可用余额为：<%=request.getAttribute("ubal")%> 感谢您的使用！<br>
</body>
</html>
<%@ page import="java.util.Enumeration" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
        <%
            String uname = request.getParameter("uname");
        %>
    <body>
        ********ATM银行系统********<br>
        欢迎尊敬的<%=uname%>！祝您心情愉快<br>
        <a href="query">查询</a><br>
        <a href="cun.jsp">存款</a><br>
        <a href="cun.jsp">取款</a><br>
        <a href="zhuan.jsp">转账</a><br>
    </body>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
    <body>
        <form action='dozhuan' method='post'>
            请您输入要转账的用户<br>
            <input type='text' name='youname' value=''><br>
            请您输入要转账的金额<br>
            <input type='text' name='zhuanbal' value=''><br>
            <input type='submit' value='确认'>
        </form>
    </body>
</html>

学习总结：
学懂的：
深入理解了一次会话和一次请求的区别，深入理解了3个内置对象的作用域
pageContext application request
有问题的地方：
中间产生的方法太多，需要后面购物系统的练习和理解。