Hi,
First off, this is not really a DWR question, but I will attempt to
give some guidance by asking a couple of questions regarding the
info below.
1. You say that you know how to write the database table trigger.
Does this mean that you know how you are going to tell the java code
that something changed in the database?
2. You would like to know how to add a row when the database table
has a new committed row. This is an excellent use of reverse ajax
and can be easily done with straight dom manipulation using
javascript, the built in dwr utilities, or using another addon
javascript framework like jQuery or prototype. What method would you
prefer to use? Do you have any restrictions?
Just taking a shot in the dark since I don't know your exact
environment... You could have the database trigger fire a call to a
servlet each time a row is committed which would then run some code
that looked like the following:
Get the script sessions that are active for the page that we want
to update. This eliminates the need to check every reverse ajax
script session that is running on the site. Once we have the
script sessions we can use the second code block to take some data
and update a table on the client side. All that the second code
section does is send javascript to the client to be executed via
the reverse ajax connection that is open.
String page = ServerContextFactory.get().getContextPath() + "/reverseajax/clock.html";
Browser.withPage(page, new Runnable() {
public void run() {
Util.setValue("clockDisplay", output);
}
});
// Creates a new Person bean.
Person person = new Person(true);
// Creates a multi-dimensional array, containing a row and the rows column data.
String[][] data = {
{person.getId(), person.getName(), person.getAddress(), person.getAge()+"", person.isSuperhero()+""}
};
// Call DWR's util which adds rows into a table. peopleTable is the id of the tbody and
// data contains the row/column data.
Util.addRows("peopleTable", data);
Note that both of the above sections of code are
pulled straight from the documentation examples @
http://directwebremoting.org/dwr-demo/.
These are only simple examples of how reverse ajax can sent data to
the client, but your exact situation seems to be more dependent on
how you receive the notification than how you update the client
screen.
Without some type of database notification to the java code I think
you will have to poll the system at set intervals. You could make
the system a little more efficient even when polling by verifying
that there are reverse ajax script sessions active for the page
before polling the database for info.
Just thoughts. Hope they help.
- Matt -
On 5/3/2011 9:55 PM, MANISH SHARMA wrote:
Hi All,
Any other approach without using triggers...?As trigger
will fired or database server and reverse ajax code will run on
application server.......So please tell me approach.
try to be more clear, i'm in lack of ideas in this problem, even
it sounds like a classic :I have spend hours trying to play around
with this but have got nowhere.
Your help is much appreciated
On Wed, May 4, 2011 at 5:53 AM, David
Marginian
<[hidden email]>
wrote:
Reverse AJAX in combination with valid Java code can solve
this problem for you. However, most of your problem is
unrelated to DWR. First you need to determine how you are
going to write your Java code to be notified when triggers
fire. Once you have that working you can look at our reverse
AJAX examples in the dwr.war to get an idea of how you can
push these updates to the browser.
On 5/3/2011 5:16 AM, MANISH SHARMA wrote:
Hi all,
Can i solve following problem using reverse ajax?
I have oracle dbTable letssay testDbTable having column
columnA and columnB.Whenever a new row is added in
database table,it should display content of that row on
JSP page in following manner.
columnA(value):----- and then columnB(value):........
lestsay after some time a new row is added in
testDbTable. then output should be in two line. Added
new row in testDbTable should be aove on previous row
that was displayed earlier on JSP page.
columnA(value):----- and then columnB(value):........
columnA(value):----- and then columnB(value):........
But such action should be at same time whenever a new
row is added.
The simplest way i could think of that check on database
again and again for some predefined lenth of time,but
this solution seems to be wasteful and suboptimal to me,
so i was wondering is there a better way.
i think there should be a trigger on table,when a new
row is added in db then trigger should be fired and
display row content on JSP page. I know "how to create
trigger on table" but after that i am blank,how will i
display just added row on JSP. After trigger on db table
how will i approach? Can Ajax solve my problem like auto
refresh or watch on db table or sothing else? is there
anyway i can listen to a trigger on my database from a
.jsp script and force my client page to be refreshed ?
Can you provide me any example link related to
ajax,oracle dbtriggers and JSP?
If you have any working example like this,please mail
me..Please show me direction
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