How to detect an error from ajax get

Question

Hi -- This is in a javascript function.
I have an object ajaxRequest defined as:
ajaxRequest = new htmldb_Get(null,&APP_ID.,'APPLICATION_PROCESS=LOOKUP_VALUE',0);
I call the app process as follows:
ajaxResponse = ajaxRequest.get();
The app process just looks up a value in the DB based on another. It works fine
when there's a match. When there's not a match, I can see that the ajaxResponse
contains "sqlerrm: ORA- ... ". And of course a json.parse fails.
How can I detect that the get returned an error? I can't just search
ajaxResponse for an string, right? (It doesn't appear that that object is
simply treated as a string... )
Thanks,
Carol

Answer 1

hi John -- Sounds good, but I guess I'm not sure how to go about it.
LOOKUP_VALUE is:
DECLARE
-- Set wwv_flow.g_x01, g_x02, g_x03, g_x04 and g_x05 in the
-- javascript part
p_source_item_value varchar2(1000) := wwv_flow.g_x01;
d_source_column_name varchar2(32) := wwv_flow.g_x02;
d_dest_column_name varchar2(32) := wwv_flow.g_x04;
d_lookup_table_name varchar2(32) := wwv_flow.g_x05;
BEGIN
--Use this to get a JSON string back in the javascript,
-- based on the SQL query
APEX_UTIL.JSON_FROM_SQL('SELECT '||d_dest_column_name||' RETURN_VAL FROM '||d_lookup_table_name||'@'||:DB_NAME||' WHERE '||d_source_column_name||' = '''|| p_source_item_value||'''');
END;
So, it's returning this JSON object to the javascript. As I said, it works fine when there's a match.
I'm not sure how to catch an error in the LOOKUP_VALUE process and get it back to the javascript. Ideas?
Also, even if I do get that going, I'm not sure how to check the returned object for some sort of problem.
The javascript function code is below. Look for #### for my comments. Essentially, right now, if
there is an error in the json object (it's showing up as a numeric or value error), the parse fails. So I
need to detect the problem before the parse. OR, if I can just modify LOOKUP_VALUE to plug in
something like 'NO MATCH' when there's a problem or no value is found, then I think json.parse will work
and my page item can just be set to NO MATCH. Does this make sense?
Here's the function.
Thanks for your help!
Carol
function jsLookupValue(source_item_value, source_column_name, dest_item_name, dest_column_name, lookup_table_name){
// Continue only if there are valid values
if (valueOf(source_column_name)&&valueOf(dest_item_name)&&valueOf(dest_column_name)&&valueOf(lookup_table_name)){
//Check to see if the source_item_value is null (either all spaces or empty
//If it is, set the dest item to null, but only if it's not already --
//otherwise we get into a loop.
source_item_value = trim(source_item_value);
dest_item_value = trim($v(dest_item_name));
if (source_item_value.length==0) {
if (dest_item_value.length != 0) {
$s(dest_item_name, null);
}else{
//This is the AJAX call to the Application Process from step 1
ajaxRequest = new htmldb_Get(null,&APP_ID.,'APPLICATION_PROCESS=LOOKUP_VALUE',0);
//Here we are adding that x01 parameter we use in the app process with the value of the objecttype_name field
ajaxRequest.addParam('x01', source_item_value);
ajaxRequest.addParam('x02', source_column_name);
ajaxRequest.addParam('x03', dest_item_name);
ajaxRequest.addParam('x04', dest_column_name);
ajaxRequest.addParam('x05', lookup_table_name);
//Now do the actual AJAX call and put the result in ajaxResponse
ajaxResponse = ajaxRequest.get();
//Check if there is a response
if (ajaxResponse) {
// ######### When there's no row matching the query, this alert shows
// "sqlerrm: ORA-06502 PL/SQL: numeric or value error"
// Can I somehow check ajaxResponse for that string?
alert("Response from APP process: " + ajaxResponse);
//We need to format the JSON return string and put it in a JSON object
// the formatting is done by a function in the external JSON library
// the jsonobj can be used to retrieve the data returned by the App process
// ######### If there was an error, the parse fails
var jsonobj= ajaxResponse.parseJSON();
alert('Filtered returned value from APP process: ' + jsonobj.row[0].RETURN_VAL);
// And finally, we set the DNAME item with the value of the jsonobj.DNAME
// an array was created in the object with the name row, so that is why you have to include row[0] to retrieve the data
if (jsonobj.row[0].RETURN_VAL != $v(dest_item_name)) {
// ########## I'd like to just set the destination item w/ something like "NO MATCH"
// probably regardless of the error...
$s(dest_item_name, jsonobj.row[0].RETURN_VAL);
}else{
//alert ('NOT setting dest item');
} //not setting
}else{
alert('No response from app process');
} //no response
} //no source item value
} //no bad nulls
} //function