Question

I’m comparing 2 URL query strings to see if they’re equal; however, I want to ignore a specific query parameter (always with a numeric value) if it exists. So, these 2 query strings should be equal:

firstName=bobby&lastName=tables&paramToIgnore=2

firstName=bobby&lastName=tables&paramToIgnore=5

So, I tried to use a regex replace using the REReplaceNoCase function:

REReplaceNoCase(myQueryString, "&paramToIgnore=[0-9]*", "")

This works fine for the above example. I apply the replace to both strings and then compare. The problem is that I can’t be sure that the param will be the last one in the string… the following 2 query strings should also be equal:

firstName=bobby&lastName=tables&paramToIgnore=2

paramToIgnore=5&firstName=bobby&lastName=tables

So, I changed the regex to make the preceding ampersand optional… "&?paramToIgnore=[0-9]*". But – these strings will still not be equal as I’ll be left with an extra ampersand in one of the strings but not the other:

firstName=bobby&lastName=tables

&firstName=bobby&lastName=tables

Similarly, I can’t just remove preceding and following ampersands ("&?paramToIgnore=[0-9]*&?") as if the query param is in the middle of the string I’ll strip one ampersand too many in one string and not the other – e.g.

firstName=bobby&lastName=tables&paramToIgnore=2

firstName=bobby&paramToIgnore=5&lastName=tables

will become

firstName=bobby&lastName=tables

firstName=bobbylastName=tables

I can’t seem to get my head around the logic of this… Can anyone help me out with a solution?

Answer 1

If you can’t be sure of the order the parameters appear i would recommend, that you don’t compare them by the string itsself.

I recommend splitting the string up like this:

String stringA = "firstName=bobby&lastName=tables&paramToIgnore=2";
String stringB = "firstName=bobby&lastName=tables&paramToIgnore=5";

String[] partsA = stringA.split("&");
String[] partsB = stringB.split("&");

Then go through arrays and make the paramToIgnore somehow euqal:

for(int i = 0; i < partsA.length; i++)
{
  if(partsA[i].startsWith("paramToIgnore"){
   partsA[i] = "IgnoreMePlease";
  }
}

for(int j = 0; j < partsB.length; j++)
{
  if(partsB[i].startsWith("paramToIgnore"){
   partsB[i] = "IgnoreMePlease";
  }
}

Then you can sort and compare the arrays to see if they are equal:

Arrays.sort(partsA);
Arrays.sort(partsB);
boolean b = Arrays.equals(partsA, partsB);

I’m pretty sure it’s possible to make this more compact and give it a better performance. But with comparing strings like you do, you somehow alsways have to care about the order of your parameters.