We have discussed the basic remote
javascripting, here I will go with advance visualforce remote javascripting.
Adavnced remote javascripting provides you flexibilty and high perfomance of
pages.
Adding JavaScript
Remoting to a Visualforce Page
To use JavaScript remoting in
a Visualforce page, add the request as a JavaScript invocation with
the following form:
[namespace.]controller.method(
[parameters...,]
callbackFunction,
[configuration]
);
namespace is the namespace of the controller class. This is required if your
organization has a namespace defined, or if the class comes from an installed
package. There are two alternatives to define remote
javascript without manually adding namespace. Below two examples generate namespace
by its own.
1. Use
remoteaction global variable.
{!$RemoteAction.classname.methodname}(
[parameters...,]
callbackFunction,
[configuration]
);
2. Use visualforce remoting
manager
Visualforce.remoting.Manager.invokeAction(
'{!$RemoteAction.AccountRemoter.getAccount}',
accountName,
handleResult
);
controller is
the name of your Apex controller.
method is
the name of the Apex method you’re calling.
parameters is the comma-separated list of parameters that your method takes.callbackFunction is the name of the
JavaScript function that will handle the response from the controller. You can
also declare an anonymous function inline. callbackFunction receives the status of the method call and the result as
parameters.
configuration configures the handling of
the remote call and response. Use this to change the behavior of a remoting
call, such as whether or not to escape the Apex method’s response.
The remote method call executes
synchronously, but it doesn’t wait for the response to return. When the
response returns, the callback function handles it asynchronously.
Here I will explain about
the configuration option in detail. The default
configuration parameters look like this:
{ buffer: true,
escape: true, timeout: 30000 }
buffer
Of type Boolean, whether to group requests executed
close to each other in time into a single request. The default is true.
JavaScript remoting optimizes
requests that are executed close to each other in time and groups the calls
into a single request. This buffering improve the efficiency of the overall
request-and-response cycle, but sometimes it’s useful to ensure all requests
execute independently.
escape
Of type
Boolean, whether to escape the Apex method’s response. The default is
true.
timeout
Of type integer, the timeout for the request, in
milliseconds. The default is 30000 (30 seconds). The maximum is 120000 (120
seconds, or 2 minutes).
The response to a remote method call is handled
asynchronously by the callback function provided in the remote method call.
Your callback function will receive as parameters an event object
representing the status of the remote call, and theresult object returned by the remote Apex method. Your
function can update information and user interface elements on the page based
on the data returned.
The event object provides
values that let you act upon the success or failure of the remote call:
event.status is true on success, false on error.
event.type is the type of the response: rpc for a
successful call, exception if the remote method threw an exception, and so on.
event.message contains any error message that is returned.
event.where contains the Apex stack trace, if one was
generated by the remote method.
Apex primitive data types returned by result—such as strings or numbers—are converted to their JavaScript
equivalents. Apex objects that are returned are converted to
JavaScript objects, while collections are converted to a JavaScript array. Keep
in mind that JavaScript is case-sensitive, so id, Id, and ID are considered
different fields.
As part of a JavaScript remote call, if the Apex method
response contains references to the same object, the object won't be duplicated
in the returned JavaScript object, and instead, the rendered JavaScript object will
contain references to the same object. An example is an Apex method
which returns a list that contains the same object twice.
By default, the response of the remote call must return
within 30 seconds, after which
the call will time out. If
your request needs longer to complete, configure a longer timeout, up to 120 seconds.
If your JavaScript remoting code is exceeding this limit,
you have several options:
Reduce the size of the response
for each request. Only return data that’s required.
Break up large data retrieval into
requests that return smaller chunks.
Ensure that you’re using
non-batched requests. Set { buffer: false } in your remoting request configuration
block.
Make batched requests less
frequently, reducing the size of the batch.
Javascript
Remoting and Action Fuction
<apex:actionFunction> component also
lets you call controller action methods through JavaScript. Here are some
differences between the two:
The <apex:actionFunction> tag:
lets you specify rerender targets
submits the form
does not require you to write any JavaScript
JavaScript remoting:
lets you pass parameters
provides a callback
requires you to write some JavaScript
In general, <apex:actionFunction> is easier to
use and requires less code, while JavaScript remoting offers more flexibility.
