Analyze the usage and classification of JSP comments

Classification and usage analysis of JSP comments

JSP comments are divided into two types:

1. Single-line comments: Starting with and ending with <code>--%>, only a single line of code can be commented.
2. Multi-line comments: Starting with /* and ending with */, you can comment multiple lines of code.

Single-line comment example

<%-- 这是一行注释 --%>

Multi-line comment example

/*
 * 这是一段多行注释
 * 可以注释多行代码
 */

Usage of JSP comments

JSP comments can be used to comment JSP code, so It's easier to read and understand. Comments can also be used to comment out some temporarily unnecessary code for later use.

The following are some usage examples of JSP comments:

1. Comment out some temporarily unnecessary code

<%-- 这段代码暂时不需要，注释掉 --%>
<p>这段代码暂时不需要</p>

2. Comment some complex code

<%-- 这段代码比较复杂，注释一下 --%>
<%
    // 这段代码比较复杂
    for (int i = 0; i < 10; i++) {
        out.println("Hello, world!");
    }
%>

3. Comment some important information

<%-- 这段代码非常重要，注释一下 --%>
<%
    // 这段代码非常重要
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    if (username.equals("admin") && password.equals("123456")) {
        // 登录成功
        session.setAttribute("user", username);
        response.sendRedirect("welcome.jsp");
    } else {
        // 登录失败
        request.setAttribute("error", "用户名或密码错误");
        request.getRequestDispatcher("login.jsp").forward(request, response);
    }
%>

Notes

1. JSP comments cannot be nested.
2. JSP comments cannot contain JSP code.
3. JSP comments cannot contain HTML code.

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