java学习笔记（四）——jsp隐式对象

response
request
session
exception
out
application(servletcontext)
pagecontext
page（servlet）
config(servletconfig)

out隐式对象

<%@page import="java.io.OutputStream"%><%@page import="java.io.FileInputStream"%><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%

String path = application.getRealPath("/1.jpg");
String filename = path.substring(path.lastIndexOf("\\")+1);
response.setHeader("content-disposition", "attachment;filename="+filename);

FileInputStream in = new FileInputStream(path);
int len= 0;
byte [] buffer = new byte[1024];

OutputStream sout = response.getOutputStream();
while((len=in.read(buffer))>0){
sout.write(buffer,0,len);
}

%>

pagecontext隐式对象

他封装了其他8个隐式对象
自己也是一个域对象，可以用来保存数据
封装了一些常用操作，比如跳转到其他资源

<%
pageContext.setAttribute("data", "xxx111222",pageContext.SESSION_SCOPE);
//String data = (String)session.getAttribute("data");
//String data = (String)pageContext.getAttribute("data",pageContext.SESSION_SCOPE);
String data = (String)pageContext.findAttribute("data");//pagecontext request session servletcontext
%>
<%=data %>

<%
//request.getRequestDispatcher("/2.jsp").forward(request,response);
pageContext.forward("/2.jsp");
%>