JSP内部对象详解

1.1 application
*在jsp中获得application对象
如：getServletContext().setAttribute("counter",new my***nt.Counter());
如：my***nter.Counter"/>
*在jsp中处理On Application Start和On Session Start事件的方法
使用HttpSessionBindingListener类.
添加session:
se***on.putValue("bi***ings.listener",new MyListener(getServletContext());
定义MyListener类：
import javax.servlet.http.*;
import javax.servlet.*;
public class MyListener implements HttpSessionBindingListener{
ServletContext context;
public MyListener(ServletContext context){
th***context=context;
}
public void valueBound(HttpSessionBindingEvent event){
Sy***m.ou***rintln("valuebound:someone just bound my listener to a session!");
}
public void valueUnbound(HttpSessionBindingEvent event){
Sy***m.ou***rintln("valueunbound:someone just unbound my listener!");
}
}

1.2 request
*获取一个正在运行时的jsp/servlet文件的绝对url地址
Stringf fi***request.getRequestURL();
if(re***t.getQueryString()!=null{
file+='?'+re***st.getqueryString();
}
URL reconstructedURL=new URL(re***st.getScheme(),re***st.getServerName(),re***st.getServerPort(),file);
ou***rintln(re***structedURL.toString());
*获取客户端通过哪一个url访问本页面
String ca***age=request.getHeader("Referer");
*获取当前脚本在当疥文件系统中的真实路径
re***st.getRealPath(re***st.getServletPath());
*判断多个submit中的一个


在jsp中使用re***st.getParameter("sub");就可分辨

1.3 response
*网页重定向之三方法
(1)re***nse.sendRedirect(url);
(2)<％re***nse.setStatus(Ht***ervletResponse.SC_MOVED_PREMANENTLY);
String nowloc="/n***ath/index.htm";
re***nse.setHeader("Location",newloc);％>
(3)/n***age.jsp"/>
注意上法只能在任何输出还没有发送到客户端之前使用这种方法
*禁用缓存
<％re***nse.setHeader("Cache-Control","no-store");
re***nse.setDateHeader("Expires",0);％>

1.4 session
*存活时间
<％se***on.setMaxInactiveInterval(300);％>
*注销
se***on.invalidate();

1.5 exception
*在jsp页面中处理Servlet的错误
protected void sendErrorRedirect(HttpServletRequest request,
HttpServletResponse response,String errorPageURL,Throwable e)
throws ServletException,IOException{
re***st.setAttibute("ja***.servlet.jsp.jspException",e);
getServletConfig().getServletContext();
getRequestDispatcher(errorPageURL).forward(request,response);
}
public void doPost(HttpServletRequest request,HttpServletResponse response){
try{
//
}
catch(Exception e){try{
sendErrorRedirect(request,response,"/j***ErrPage.jsp",e);
}catch(Exception e){e.***ntStackTrace();}
}
}
*在jsp页面中输出错误的stacktrace
(1)
<％@ page isErrorPage="true％>
<％
ou***rintln("

");
printWriter pw***sponse.getWriter();
ex***tion.printStackTrace(pw);
ou***rintln("

<％
ex***tion.printStackTrace(new PrintWriter(out));
％>

1.6 Cookie
*设置cookie
<％
Cookie mycookie=new Cookie("aName","aValue");
re***nse.addCookie(mycookie);
//***ookie.setMaxAge(time);
％>