Thank you for answers.. everything is ok now... Regards
On 18 mai, 22:43, Blessed Geek <blessedg...@gmail.com> wrote: > Why asynchronous? > > This is a classic examination question in data communications. > > Why serializable? - another classic examination question. > > Classic - meaning that the professors in data communication would want > to ensure you understand them before they would like you to be given a > piece of paper to pass through the pearly gates of their academic > institutions to make your contributions to the data engineering world. > > Asynchronous > ========== > Remember the days of pure JSP and HTML pages and absence of AJAX? You > would have a page with multiple cells. Your user would need to fill up > the page cells, click on submit. Then the page blanks off for a while. > Sometimes it is longer than a while. Sometimes, you need to send an > intervening page to say, "server still processing, please be patient". > > We used to ask, why couldn't we just send the request out without > refreshing the page. Why can't the web page be allowed to continue to > function while waiting for the response? For example, for a page > displaying the price trend of a stock, when a request is sent to the > server to refresh the stock price, I would like to continue being able > to zoom in and out of the chart of its historical prices. In the old > days, we would click on a submit button, the screen blanks off and we > go get a cup of coffee and then the browser relents to display the > page when the server finally sends its response. > > So asynchrony is a desirable condition, not a disadvantage. You may > ask, why can't the browser display the response as soon as possible > rather than wait asynchronously. The browser not displaying as soon as > possible is not the fault of asynchrony. It is the fault of slow > servers and faulty data cables - that we use asynchrony as a > compensatory measure. If you don't like asynchrony, you could revert > back to the old days of a blanked screen waiting for the server to > respond. Or spend a lot of money upgrading your servers and data > cabling. > > Serializable > ======== > Imagine Moses and the Red sea. Let us say that the angel opened up the > a passage in the Red sea to allow only a single file of people to pass > through. The Pharaoh's army is behind pursuing the Israelites and > Moses has to make sure his people get across to the other side of the > sea as quickly as possible. > > So the Israelites are now assembled according to tribe, and then by > clan, and then by family. They stick together in that hierarchy. But > the passage across the sea allows only one person row of people. So > Moses has to break the tribes, clans and families up and marshal them > into a single row of people. And then on the other side, he has to > ensure they are able to reassemble them back into their tribe, clan > and family hierarchy. You wouldn't want Moses faced with the situation > of a child, on reaching the other side, crying "where is my mummy and > daddy?", would you? > > There is a data communication channel between your browser (where you > might be sitting in a cafe in Ougadougou) and the server (sitting > somewhere in Mumbai). You might not be aware of that if you are on > development mode where your browser, server and Eclipse sits on the > same machine, wondering why can't they just pass objects to each other > by sharing the computer's memory. But you are developing for a remote- > to-remote situation where the data lines, in theory, require you to > send your objects in a serial manner. > > By implementing Serializable, you are telling the data communication > channel where to find the disassembling/serializing routines and then > where to find the reassembly/deserializing routines for your > object.Most classes already come with serializing/deserializing > routines so you only need to implement Serializable, otherwise you > would need to write the serializer/deserializer. > > If you are developing using the Google Plugin for Eclipse, you need to > turn the GAE option off if you are not developing for GAE. When you > develop for GAE, or any cloudified environment, your application needs > its sessions to be allowed to shift from server to server across the > world. That is how the cloud owner would like to optimise their > resources and the response of your application. In order to facilitate > that kind of shift, your objects need to be serializable. > > -- > You received this message because you are subscribed to the Google Groups > "Google Web Toolkit" group. > To post to this group, send email to google-web-tool...@googlegroups.com. > To unsubscribe from this group, send email to > google-web-toolkit+unsubscr...@googlegroups.com. > For more options, visit this group > athttp://groups.google.com/group/google-web-toolkit?hl=en. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to google-web-tool...@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
