JSP学习------为何jsp是servlet?
Posted 晓锋残月
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1.jsp基本介绍
(1)jsp解释JSP全称是Java Server Pages,它和servle技术一样,都是SUN公司定义的一种用于开发动态web资源的技术。JSP/Servlet规范。JSP实际上就是Servlet。
(2)jsp的执行过程
通常jsp要经历“翻译--------编译”过程,翻译将jsp页面变成.java文件,编译将.java文件变成.class文件。
图解为下面所示:
下面以一个单的例子测试:
<%@page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
Date date=new Date();
out.print(date.toLocaleString());
%>
</body>
</html>
部署成功后,在下面路径:D:\\javatool\\apache-tomcat-7.0.75\\work\\Catalina\\localhost\\ee12_jsp\\org\\apache\\jsp得到
(3)对翻译的jsp页面解读
在_1_jsp.java页面中有下面代码(只保留了部分代码)
public final class _1_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent
public void _jspInit()
public void _jspDestroy()
public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
throws java.io.IOException, javax.servlet.ServletException
out.write("\\r\\n");
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("<head>\\r\\n");
out.write("<meta http-equiv=\\"Content-Type\\" content=\\"text/html; charset=UTF-8\\">\\r\\n");
out.write("<title>Insert title here</title>\\r\\n");
out.write("</head>\\r\\n");
out.write("<body>\\r\\n");
out.write("\\t");
Date date=new Date();
out.print(date.toLocaleString());
out.write("\\r\\n");
out.write("</body>\\r\\n");
out.write("</html>");
①可以看 _1_jsp extends org.apache.jasper.runtime.HttpJspBase, 表示其继承了HttpJspBase类,往下看HttpJspBase的源码
public abstract class HttpJspBase extends HttpServlet implements HttpJspPage
private static final long serialVersionUID = 1L;
protected HttpJspBase()
@Override
public final void init(ServletConfig config)
throws ServletException
super.init(config);
jspInit();
_jspInit();
@Override
public String getServletInfo()
return Localizer.getMessage("jsp.engine.info");
@Override
public final void destroy()
jspDestroy();
_jspDestroy();
/**
* Entry point into service.
*/
@Override
public final void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
_jspService(request, response);
@Override
public void jspInit()
public void _jspInit()
@Override
public void jspDestroy()
protected void _jspDestroy()
@Override
public abstract void _jspService(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException;
综上可以得到 _1_jsp.java继承了HttpServlet,故可以说JSP就是Servlet。
②jsp页面的html元素最终以out.write("<html>");的形式输出。
③在_1_jsp.java的代码中,同样有servlet有的init、serve、destroy等方法。
2.总结:
以上便是对于jsp的初步学习,如果有错误,请告知,谢谢!
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