Friday, June 29, 2007

LoadRunner function: web_convert_param

After spending about 6 hours trying to figure out a solution to the problem of parameterizing URL encoded strings in my LoadRunner script, I finally found the solution: a built-in function provided by LR.

The problem:
I recently recorded a script against an Java application that ultimately sends a HTTP POST request to the server being tested with an XML in the Body of the request. The script came out fine, except that the body (XML content) was URL encoded. It would have been fine if I didn't need to parameterize the data in the body but since I had to, I realized in a few seconds that I would have to do some extra work to convert the data from parameter file to URL encoded format. The data in parameter file is of the form:


However, in the script, address is one field that is a concatenated string of A1 - A5 parameters with a space between each of them.

Further Research:
A1 - A5 are the components that make up the street address that is supposed to be concatenated to one field in the script. No problem.
sprintf(as,"%s %s %s %s %s", lr_eval_string("{a1}"), lr_eval_string("{a2}"), lr_eval_string("{a3}"), lr_eval_string("{a4}"), lr_eval_string("{a5}"));
lr_save_string(as, "addressStreet");

…but the problem is there are spaces in between this components, which we all know get converted to a '+' character in URL encoding. Ok, so I could've just used sprintf(as,"%s+%s+%s+%s+%s",…
But some of the addresses also have '#' signs that get converted into '%23'. Now I had 2 options:
1. remove all the addresses that have a '#' sign
2. write a URLEncode(char *) function that does the obvious.

1st option wasn't very tempting because however unlikely it may be, the addresses can have other characters that need to get URL encoded as well. And if a sizeable chunk of the data given to me has these characters, I could lose a lot of records. Also I didn't want to have to modify the data every time I get a new 10,000 record file.
2nd option seemed the way to go. But it was late Friday and I had to start the tests in a short time so I was lacking the much needed patience. Anyways, I ended up running my tests by removing the records with '#' character. Luckily, there were few.

On Monday after running all the tests, I got back to writing the URLEncode function. After researching online on what the characters should get converted to and trying to find an already published function in C that I could tweak to my purpose, and stumbling on PHP, Java, JavaScript functions, I started getting a sense that LR may have some kind of built-in function that does that or something similar. I don't know why I hadn't thought of using Mercury Knowledgebase before that. So a simple search of "url encoding" brought up 3 articles - none of which seemed helpful. But reading through the 2nd one (KB Problem ID: 18880), I couldn't believe what I saw:
Pass the 'XMLSource' parameter as an input to the web_convert_param function, and store the result as 'TargetXML'
web_convert_param("TargetXML", "SourceString={XMLSource}", "SourceEncoding=HTML", "TargetEncoding=URL", LAST);

So this web_convert_param function seemed to do exactly what I needed. I tried it out with a couple of different strings and it did as promised. So my new script had:
sprintf(as,"%s %s %s %s %s", lr_eval_string("{a1}"), lr_eval_string("{a2}"), lr_eval_string("{a3}"), lr_eval_string("{a4}"), lr_eval_string("{a5}"));
lr_save_string(as, "addressStreet");

web_convert_param("encAddressStreet", "SourceString={addressStreet}", "SourceEncoding=PLAIN", "TargetEncoding=URL", LAST);
lr_output_message("%s", lr_eval_string("{encAddressStreet}"));

It took me only a few minutes to make that change. And I didn't need to worry about the '#' characters or any other unsafe characters in the address string. Phew…

Use the Mercury Knowledgebase more often. If you think there should be any other, let me know.