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In-depth exploration of the functions and usage of JSP built-in objects

王林

Jan 13, 2024 am 08:15 AM

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In-depth exploration of the functions and usage of JSP built-in objects

In-depth analysis of the role and usage of JSP built-in objects

JSP (JavaServer Pages) is a dynamic web page technology that can embed Java code into HTML pages, making The display content of the web page can be dynamically generated based on business logic. In JSP, there are some built-in objects that can be used directly and provide us with many convenient functions. This article will focus on the commonly used built-in objects in JSP, their functions and usage, and give specific code examples.

request object

The request object represents the HTTP request sent by the client to the server. The parameter information, request header information, and cookies sent by the client can be obtained through the request object. wait.

<%@ page language="java" %>
<%
    String name = request.getParameter("name");
    String age = request.getParameter("age");
%>
<html>
<head>
    <title>JSP内置对象示例</title>
</head>
<body>
    <h2 id="获取到的参数信息">获取到的参数信息：</h2>
    <p>姓名： <%= name %></p>
    <p>年龄： <%= age %></p>
</body>
</html>

response object

The response object represents the server's response to the client. You can set response headers, send cookies, etc. through the response object.

<%@ page language="java" %>
<%
    response.setContentType("text/html;charset=UTF-8");
    response.setHeader("Cache-Control", "no-cache");
    response.addCookie(new Cookie("username", "admin"));
%>
<html>
<head>
    <title>JSP内置对象示例</title>
</head>
<body>
    <h2 id="设置响应头和Cookie成功">设置响应头和Cookie成功！</h2>
</body>
</html>

session object

The session object represents a user session and can share data between different pages. Through the session object, we can store the user's login status, shopping cart data, etc.

<%@ page language="java" %>
<%
    session.setAttribute("username", "admin");
%>
<html>
<head>
    <title>JSP内置对象示例</title>
</head>
<body>
    <h2 id="用户登录状态">用户登录状态：</h2>
    <% if (session.getAttribute("username") != null) { %>
        <p>欢迎， <%= session.getAttribute("username") %>！</p>
        <a href="logout.jsp">退出登录</a>
    <% } else { %>
        <p>未登录，<a href="login.jsp">点击登录</a></p>
    <% } %>
</body>
</html>

application object

The application object represents the entire application and can share data between different users. Through the application object, we can store global configuration information, cache data, etc.

<%@ page language="java" %>
<%
    application.setAttribute("version", "1.0.0");
%>
<html>
<head>
    <title>JSP内置对象示例</title>
</head>
<body>
    <h2 id="应用程序版本信息">应用程序版本信息：</h2>
    <p>当前版本： <%= application.getAttribute("version") %></p>
</body>
</html>

out object

The out object is used to send content to the client. Text, HTML code, etc. can be output through the out object.

<%@ page language="java" %>
<%
    String message = "Hello, JSP!";
    out.println(message);
%>

pageContext object

The pageContext object is the top-level object of other built-in objects, and other built-in objects can be accessed through the pageContext object. For example, the request object can be obtained through pageContext.getRequest().

<%@ page language="java" %>
<%
    String name = pageContext.getRequest().getParameter("name");
%>
<html>
<head>
    <title>JSP内置对象示例</title>
</head>
<body>
    <h2 id="获取到的参数信息">获取到的参数信息：</h2>
    <p>姓名： <%= name %></p>
</body>
</html>

Through in-depth analysis of JSP built-in objects, we can better understand and use these objects and improve efficiency and quality when developing Web applications. I hope this article can be helpful to everyone.

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