我们打开tomcat的D:\Program_Files\apache-tomcat-8.0.32\work\Catalina\localhost\venus\org\apache\jsp，
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("\r\n");
out.write("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\r\n");
out.write("<html>\r\n");
out.write("\t<head>\r\n");
out.write("\t\t<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n");
out.write("\t\t<title>百度一下</title>\r\n");
out.write("\t</head>\r\n");
out.write("\t<body>\r\n");
out.write("\t\t<form action=\"./DoLoginServlet\" method=\"post\">\r\n");
out.write("\t\t\t<input name=\"user_name\">\r\n");
out.write("\t\t\t<input type=\"password\" name=\"password\">\r\n");
out.write("\t\t\t<button type=\"submit\">提交</button>\r\n");
out.write("\t\t</form>\r\n");
out.write("\t\t\r\n");
out.write("\t</body>\r\n");
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