JAVA regex indentify values and classify path params

Question

currently I have a table that saves the logs for each change in the endpoints, however I need to show on screen to the user which endpoint has been changed, and which Id's have been sent. I currently have these examples:

/admin/account/bot/6/layout/properties
/admin/bot/4/block/content/button/34/label
/admin/bot/4/block/content/text/18/message

it is possible to make a regular expression to classify each endpoint, for example:

/admin/account/bot/6/layout/properties
name: Update Bot properties
BotId: 6

/admin/bot/4/block/content/text/18/message
name: Update message in Text
BotId: 4
TextId: 18

and extract each value ?

thanks.

rzwitserloot · Accepted Answer · 2020-12-01 16:01:27Z

Depends on the exact structure of the strings you are trying to match; not everything is regular. A basic approach here would be:

private static final Pattern ACCOUNT_PROPERTIES = 
  Pattern.compile("/admin/account/bot/(\\d+)/layout/properties");
private static final Pattern BLOCK_CONTENT = 
  Pattern.compile("/admin/bot/(\\d+)/block/content/(\\w+)/(\\d+)/(\\w+)");

public void handle(String path) {
   Matcher m;

   m = ACCOUNT_PROPERTIES.matcher(path);
   if (path.matches()) {
       handlePropertiesUpdate(Integer.parseInt(m.group(1)));
       return;
   }

   m = BLOCK_CONTENT.matcher(path);
   if (path.matches()) {
       int botId = Integer.parseInt(m.group(1));
       String objType = m.group(2);
       int objId = Integer.parseInt(m.group(3));
       String updType = m.group(4);
       handleBlockContent(botId, objType, objId, updType);
   }

   throw new NotAcceptedException();
}

etcetera.

Trying to make one regexp to catch it all seems... ill-advised. It'd be one heck of a job to try to figure out which group goes where, and an update in one of these structures would then neccessity updating all your code. There are ways to name groups, which is a slight improvement, but you're still looking at a gigantic regexp. If the aim is to 'make it run faster by running less code', I have bad news. Regexps make no guarantees about performance and have O(n^2) worst case if you use certain regex features. If you want speed, steer away from them, or at least be an expert so you know what and how to make them run quickly.

Tim Biegeleisen · Accepted Answer · 2020-12-01 15:57:44Z

0

I don't know of a foolproof way to generate the exact names you expect here, but as for the key-value pairs, a regex pattern matcher can handle this:

String input = "/admin/bot/4/block/content/button/34/label";
String pattern = "/(\\w+)/(\\d+)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(input);

while (m.find( )) {
    System.out.println(m.group(1) + "Id: " + m.group(2));
}

This prints:

botId: 4
buttonId: 34

answered Dec 1, 2020 at 15:57

Tim Biegeleisen

526k32 gold badges323 silver badges399 bronze badges

Collectives™ on Stack Overflow

JAVA regex indentify values and classify path params

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related