JSP built-in object programming skills

js| Programming | objects | techniques | Built-in Objects 1.1 application


* Get Application object in JSP


such as: Getservletcontext (). setattribute ("Counter", New mycount. Counter ());


such as: <jsp:usebean scope= "Application id=" counter "class=" mycounter. Counter "/>


* methods to handle on application start and on session start events in a JSP


uses the Httpsessionbindinglistener class.


Add session:


session.putvalue ("Bingdings.listener", New MyListener (Getservletcontext ());


definition MyListener class:


import javax.servlet.http.*;


import javax.servlet.*;


public class MyListener implements httpsessionbindinglistener{


ServletContext context;


Public MyListener (ServletContext context) {


This.context=context;


}


public void Valuebound (Httpsessionbindingevent event) {


System.out.println ("Valuebound:someone just bound I listener to a session!");


}


public void Valueunbound (Httpsessionbindingevent event) {


System.out.println ("Valueunbound:someone just unbound my listener!");


}


}





1.2 Request


* Gets an absolute URL address for a jsp/servlet file that is running


STRINGF File=request.getrequesturl ();


if (requet.getquerystring ()!=null{


file+= '? ' +request.getquerystring ();


}


url reconstructedurl=new url (request.getscheme (), Request.getservername (), Request.getserverport (), file);


out.println (reconstructedurl.tostring ());


* Get the client through which URL to access this page


String callpage=request.getheader ("Referer");


* Get the real path of the current script in the Scabies file system


Request.getrealpath (Request.getservletpath ());


* To judge a
in multiple submit

<input type=submit name= "sub" value= "Up" >


<input type=submit name= "sub" value= "Down" >


Use Request.getparameter ("sub") in the JSP, and you can distinguish the





1.3 Response

Three methods of
* Web page redirection


(1) response.sendredirect (URL);


(2) <%response.setstatus (httpservletresponse.sc_moved_premanently);


String nowloc= "/newpath/index.htm";


Response.setheader ("Location", Newloc);%>


(3) <jsp:forward page= "/newpage.jsp"/>


Note the above method can only be used before any output has been sent to the client


* Disable Caching


<%response.setheader ("Cache-control", "No-store");


Response.setdateheader ("Expires", 0);%>





1.4 Session


* Survival Time


<%session.setmaxinactiveinterval (;%>)


* Cancellation


session.invalidate ();





1.5 Exception


* error handling Servlet in JSP page


protected void Senderrorredirect (HttpServletRequest request,


httpservletresponse response,string errorpageurl,throwable e)


throws servletexception,ioexception{


Request.setattibute ("Javax.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, "/jsp/errpage.jsp", e);


}catch (Exception e) {e.printstacktrace ();}


}


}


* Output the wrong stacktrace in the JSP page


(1)


<%@ page iserrorpage= "true%>


<%


out.println ("<pre>");


PrintWriter pw=response.getwriter ();


exception.printstacktrace (PW);


out.println ("</pre>");


%>


(2)


<%@ page iserrorpage= "true%>


<pre>


<%


Exception.printstacktrace (New PrintWriter (out));


%>


</pre>





1.6 Cookie


* Set Cookie


<%


Cookies Mycookie=new Cookies ("Aname", "avalue");


Response.addcookie (MyCookie);


//mycookie.setmaxage (time);


%>


。