1 . Which security protocol or measure would provide the greatest protection for a wireless LAN? WPA2 cloaking SSIDs shared WEP key MAC address filtering 2 . Refer to the exhibit. All trunk links are operational and all VLANs are allowed on all trunk links. An ARP request is sent by computer 5. Which device or devices will receive this message? only computer 4 computer 3 and RTR-A computer 4 and RTR-A computer 1, computer 2, computer 4, and RTR-A computer 1, computer 2, computer 3, computer 4, and RTR-A all of the computers and the router 3 . Refer to the exhibit. Hosts A and B, connected to hub HB1, attempt to transmit a frame at the same time but a collision occurs. Which hosts will receive the collision jamming signal? only hosts A and B only hosts A, B, and C only hosts A, B, C, and D only hosts A, B, C, and E 4 . Refer to the exhibit. Router RA receives a packet with a source address of 192.168.1.65 and a destination address of 192.168.1.161...
If I understand you well, you want to show a progress bar until your server is ready to send a file, not to show the progress of the file beeing downloaded.
ReplyDeleteIf that is true, you're dealing with a tough excercise. A reliable progressbar needs to know (pretty exact) what you're doing and how long it will take. In your case, there are lots of unreliable factors (one of them, maybe the biggest, is the web itself).
So most developers use some kind of an "endless" animation to display "work in progress".
update
Based on your comment, the easiest way to display a "work in progress" animation would look like
$.ajax({
url: "/myscripts/myserverscript",
type: "POST",
data: {
foo: "bar"
},
dataType: "text",
beforeSend: function(xhr){
// display a progress animation
},
complete: function(xhr, status){
// hide the animation
}
...
});
In the case of a single request. You may also setup a global ajax event handler for both (.ajaxStart() and .ajaxStop()) to setup the show/hide functionallity.
References: .ajax(), .ajaxStart(), .ajaxStop()
progress bar for server side file generation:
ReplyDeleteWe assume that the server needs many seconds to generate the file. This event is triggered by the original request, a blocking operation. When this finishes the file will have been generated and it'll be dispatched back to the client.
At the same time you want, via other requests (ajax), to be calling the server and getting a percentage back for the file which is currently being generated for the particular user.
The glue parts here are:
when the original request is generating the file it needs to store the progress in frequent intervals (i.e every 10%). Storing this data in the http session will work OK.
the other requests (ajax) simply need to be able to pull this information out of the http session
synchronizing (serializing access) on the http session, something that some web apps commonly do, is out of the question, since the other requests (ajax) would simply block until the original request finished
on the client side it's all html+javascript to provide the interaction you need (animated progress bar). Even if the intervals are very rough (jumping from 10% to 20% to 30%) you can animate the bar with jQuery. I've done it once in the past and it looks great.
progress bar for file download:
it's best to leave this to the browser's native dialog.
In Java you just wrap a javax.swing.ProgressMonitorInputStream around the input stream, but be aware that unless the server is sending in chunked streaming mode the display won't really mean anything, as the entire response will have been read into memory before the first byte is delivered to Java.
ReplyDelete