【jsp】入门

程序员文章站 2022-06-01 22:24:02

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再来了解一下jsp吧。。现在好像都不用jsp了
取而代之的是常见的模板引擎，比如thyme leaf

servlet
不适合设置HTML响应体，需要大量的response.getWriter().print("<html>")
动态资源，可以编程

HTML
静态页面，不能包含动态信息

jsp
在HTML基础上添加Java脚本，构成jsp页面

java脚本示例
【jsp】入门

print方法老不好使，原来要加一个lib，选tomcat就好了

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 12:04
  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>
  This is my JSP page. <br>
  <%
    int a = 10;
  %>
  <%
    out.print(a);
  %>
  <br/>
  <%=a %>

  <table border="1" align="center" width="60%">
    <tr>
      <td>name</td>
      <td>age</td>
    </tr>
    <%
      for (int i = 0; i < 10; i++) {
    %>
    <tr>
      <td>Tom</td>
      <td>33</td>
    </tr>
    <%
      }
    %>
  </table>
  </body>
</html>

【jsp】入门

jsp与servlet合作

【jsp】入门

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 15:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>form.jsp</title>
</head>
<body>
    <form action="/AServlet" method="post">
        整数1 <input type="text" name="num1"/><br>
        整数2 <input type="text" name="num2"/><br>
        <input type="submit" value="提交">
    </form>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 15:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>result.jsp</title>
</head>
<body>
<%
    Integer result = (Integer)request.getAttribute("result");
%>
<%=result%>
</body>
</html>

AServlet

package cn.it.web.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author KNOE
 * @date 2020-09-20 15:47
 */
public class AServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String s1 = request.getParameter("num1");
        String s2 = request.getParameter("num2");

        int num1 = Integer.parseInt(s1);
        int num2 = Integer.parseInt(s2);
        //calculate
        int sum = num1 + num2;
        //保存到request域中
        request.setAttribute("result", sum);
        //转换到result.jsp
        request.getRequestDispatcher("/add/result.jsp")
                .forward(request, response);
    }

}

web

<?xml version="1.0" encoding="UTF-8"?>
<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_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>AServlet</servlet-name>
        <servlet-class>cn.it.web.servlet.AServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>AServlet</servlet-name>
        <url-pattern>/AServlet</url-pattern>
    </servlet-mapping>
</web-app>

新建servlet的时候，不要选这个
【jsp】入门
这样会在xml中自动生成servlet
但是mapping还得自己写

【jsp】入门

cookie

【jsp】入门
a.jsp

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:10
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>a.jsp</title>
</head>
<body>
<h1>保存cookie</h1>
<%
    Cookie cookie1 = new Cookie("aaa", "AAA");
    response.addCookie(cookie1);

    Cookie cookie2 = new Cookie("bbb", "BBB");
    response.addCookie(cookie2);
%>
</body>
</html>

b.jsp

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:10
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>b.jsp</title>
</head>
<body>
<h1>获取cookie</h1>
<%
    Cookie[] cookies = request.getCookies();
    if (cookies != null) {
        for(Cookie c: cookies){
            out.print(c.getName() + "=" + c.getValue() + "<br/>");
        }
    }
%>
</body>
</html>

【jsp】入门
再进入b.jsp

session

session底层依赖cookie
【jsp】入门
a.jsp

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:29
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>a.jsp</title>
</head>
<body>
<h1>向session域保存数据</h1>
<%
    //已经创建了session变量
    session.setAttribute("aaa", "AAA");
%>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:30
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>b.jsp</title>
</head>
<body>
<h1>获取session中的数据</h1>
<%
    String s = (String)session.getAttribute("aaa");
%>
<%=s%>
</body>
</html>

【jsp】入门

httpSession实例

原来改了src要restart server找了半天没找到问题
【jsp】入门
LoginServlet

package cn.it.servlet;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;

/**
 * @author KNOE
 * @date 2020-09-20 16:41
 */
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //校验
        if(!"it".equalsIgnoreCase(username)){
            /**
             * 把用户名保存到cookie中 发送给客户端浏览器
             * 当再次打开login.jsp时 会读取request中的cookie
             * 显示到用户名文本框中
             */
            Cookie cookie = new Cookie("uname", username);
            cookie.setMaxAge(60 * 60 * 2); //设置时长2h
//            cookie.setPath("/");
            response.addCookie(cookie);
            /**
             * 正确
             * 保存用户信息到session中
             * 重定向到succ1.jsp
             */
            HttpSession session = request.getSession();
            session.setAttribute("username", username);
            response.sendRedirect("/session2/succ1.jsp");
        }else {
            /**
             * 错误
             * 保存错误信息到request中
             * 转发到login.jsp
             */
            request.setAttribute("msg", "用户名或密码错误！");
            //得到转发器
            RequestDispatcher rd = request.getRequestDispatcher("/session2/login.jsp");
            rd.forward(request, response); //forward
        }
    }

}

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:41
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login.jsp</title>
</head>
<body>
<%-- 本页面提供登陆表单 还显示错误信息--%>
<h1>登陆</h1>
<%
    /**
     * 读取名为uname的cookie
     * 如果为空 显示''
     * 如果不为空 显示cookie的值
     */
    String uname = "";
    Cookie[] cs = request.getCookies();
    if (cs != null) {
        //如果存在cookie
        for (Cookie c : cs) {
            //查找名为uname的cookie
            if("uname".equals(c.getName())) {
                uname = c.getValue();
            }
            out.print(c.getName() + "=" + c.getValue() + "<br/>");
        }
    }
%>
<%
    String message = "";
    String msg = (String) request.getAttribute("msg");
    if (msg != null) {
        message = msg;
    }
%>
<font color="red"><b><%=message %></b></font>
<form action="/LoginServlet" method="post">
    <%--把cookie中的用户名显示到文本框中--%>
    用户名 <input type="text" name="username" value="<%=uname%>"/><br>
    密  码 <input type="password" name="password"><br>
    <input type="submit" value="登陆">
</form>
</body>
</html>

succ1

<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2020/9/20
  Time: 16:40
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>succ1.jsp</title>
</head>
<body>
<h1>succ1</h1>
<%
    String username = (String)session.getAttribute("username");
    if (username == null) {
        //向request域中保存错误信息 转发到login.jsp
        request.setAttribute("msg", "您还没有登陆 请走正门");
        request.getRequestDispatcher("/session2/login.jsp")
                .forward(request, response);
        return;
    }
%>
欢迎<%=username%>!
</body>
</html>

succ2与succ1完全一样，表示由于session存在，不需要重新登陆

web

<?xml version="1.0" encoding="UTF-8"?>
<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_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>cn.it.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/LoginServlet</url-pattern>
    </servlet-mapping>
</web-app>

JavaBean

必须有一个默认构造器
提供get/set方法，如果只有get，那么这个属性是只读的

【jsp】入门

jsp与servlet合作

cookie

session

httpSession实例

JavaBean

jsp获取HTMLform中数据的方法

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【jsp】入门

jsp与servlet合作

cookie

session

httpSession实例

JavaBean

jsp获取HTMLform中数据的方法

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