我们打开tomcat的D:Program_Filesapache-tomcat-8.0.32workCatalinalocalhostvenusorgapachejsp，
当我们访问过页面后会发现login.jsp会生成两个文件login_jsp.class和login_jsp.java
我们打开java文件其中有这段代码
out.write("
");
out.write("<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
");
out.write("<html>
");
out.write(" <head>
");
out.write(" <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
");
out.write(" <title>百度一下</title>
");
out.write(" </head>
");
out.write(" <body>
");
out.write(" <form action="./DoLoginServlet" method="post">
");
out.write(" <input name="user_name">
");
out.write(" <input type="password" name="password">
");
out.write(" <button type="submit">提交</button>
");
out.write(" </form>
");
out.write("
");
out.write(" </body>
");
out.write("</html>");
发现原理JSP里的内容变成了字符串
JSP文件是在一个类中的