I am working with REGEX on complex JSON representing objects, each represented by UUID's. The problem is the REGEX that matches each individual object also matches a larger pattern. Take, for example, the following:
{_id:"(UUID)" value:"x"}(additional info here),{_id:"(UUID)" value:"y"}(additional info here)
now if I do a pattern such as /{_id:"(.+?)".+value:"(.+?)"}/g to grab the ID and Value of each, instead of matching each one individually will it not match the larger pattern, that being the first id and the last value?
What's the best way to ensure each group is individually pulled and not a larger pattern which also matches?
The problem with you regex /{_id:"(.+?)".+value:"(.+?)"}/g
was that .+ should be .+?
So now the regex is:
{_id:"(.+?)".+?value:"(.+?)"}/g
https://regex101.com/r/xK0qJ8/2
I was able to figure it out, I wasn't using the non-greedy "?" correctly. I was able to get each one individually by using the following:
/{_id:"(.+?)".+?value:"(.+?)"}/g
Related
Yeah there is! I made this question to share my knowledge, Q&A style since I had a hard time finding it myself :)
Thanks to https://stackoverflow.com/a/67821482/1561441 (Barbaros Özhan, see comments) for pointing me into the correct direction
The answer is: look here and here
Correct me if I'm wrong, but: Wow, currently to my knowledge a single .java file on GitHub, last commit in 2017, holds relevant parts of the official documentation of the JOLT syntax. I had to use its syntax since I'm working with NiFi and applied its JoltTransformJSON processor (hence the SEO abuses in my question, so more people find the answer)
Here are some of the most relevant parts copied from https://github.com/bazaarvoice/jolt/blob/master/jolt-core/src/main/java/com/bazaarvoice/jolt/Shiftr.java and slightly edited. The documentation itself is more extensive and also shows examples.
'*' Wildcard
Valid only on the LHS ( input JSON keys ) side of a Shiftr Spec
The '*' wildcard can be used by itself or to match part of a key.
'&' Wildcard
Valid on the LHS (left hand side - input JSON keys) and RHS (output data path)
Means, dereference against a "path" to get a value and use that value as if were a literal key.
The canonical form of the wildcard is "&(0,0)".
The first parameter is where in the input path to look for a value, and the second parameter is which part of the key to use (used with * key).
There are syntactic sugar versions of the wildcard, all of the following mean the same thing; Sugar : '&' = '&0' = '&(0)' = '&(0,0)
The syntactic sugar versions are nice, as there are a set of data transforms that do not need to use the canonical form, eg if your input data does not have any "prefixed" keys.
'$' Wildcard
Valid only on the LHS of the spec.
The existence of this wildcard is a reflection of the fact that the "data" of the input JSON, can be both in the "values" and the "keys" of the input JSON
The base case operation of Shiftr is to copy input JSON "values", thus we need a way to specify that we want to copy the input JSON "key" instead.
Thus '$' specifies that we want to use an input key, or input key derived value, as the data to be placed in the output JSON.
'$' has the same syntax as the '&' wildcard, and can be read as, dereference to get a value, and then use that value as the data to be output.
There are two cases where this is useful
when a "key" in the input JSON needs to be a "id" value in the output JSON, see the ' "$": "SecondaryRatings.&1.Id" ' example above.
you want to make a list of all the input keys.
'#' Wildcard
Valid both on the LHS and RHS, but has different behavior / format on either side.
The way to think of it, is that it allows you to specify a "synthentic" value, aka a value not found in the input data.
On the RHS of the spec, # is only valid in the the context of an array, like "[#2]".
What "[#2]" means is, go up the three levels and ask that node how many matches it has had, and then use that as an index in the arrays.
This means that, while Shiftr is doing its parallel tree walk of the input data and the spec, it tracks how many matches it has processed at each level of the spec tree.
This useful if you want to take a JSON map and turn it into a JSON array, and you do not care about the order of the array.
On the LHS of the spec, # allows you to specify a hard coded String to be place as a value in the output.
The initial use-case for this feature was to be able to process a Boolean input value, and if the value is boolean true write out the string "enabled". Note, this was possible before, but it required two Shiftr steps.
'#' Wildcard
Valid on both sides of the spec.
The basic '#' on the LHS.
This wildcard is necessary if you want to put both the input value and the input key somewhere in the output JSON.
Thus the '#' wildcard is the mean "copy the value of the data at this level in the tree, to the output".
Advanced '#' sign wildcard
The format is lools like "#(3,title)", where "3" means go up the tree 3 levels and then lookup the key "title" and use the value at that key.
I would love to know if there is an alternative to JoltTransformJSON simply because I'm struggling a lot with understanding it (not coming from a programming background myself). When it works (thanks to all the help here) it does simplify things a lot!
Here are a few other sites that help:
https://intercom.help/godigibee/en/articles/4044359-transformer-getting-to-know-jolt
https://erbalvindersingh.medium.com/applying-jolttransform-on-json-object-array-and-fetching-specific-fields-48946870b4fc
https://cool-cheng.blogspot.com/2019/12/json-jolt-tutorial.html
I'm using MySQL, and I am trying to find common strings over a given character length within a series of messages that are highly dynamic, Each message may have a common phrase, but they will be appended with reference codes or names that don't match a specific format on either side of the string. for example, this is an example of the types of common phrases I'm trying to scan for, but has dynamic content embedded as well, and in different formats (https://screencast.com/t/rlABTWitQ)
The end result I am looking for is something akin to this (https://screencast.com/t/qXzrGNFuf)
Because of the highly variable nature of the formats of these messages, uses of substring_index and regexp (as much as my amateur familiarity with REGEXP has taken me), I can't seem to get anything going
SELECT LEFT("first_middle_last", CHAR_LENGTH("first_middle_last") - LOCATE('_', REVERSE("first_middle_last")));
I can't use something like this, as it would just strip out on a specific type of character. As you can see, the types of strings are too variant in format
I have this one line JSON text:
{"schemaText":{"fields":[{"name":"AX_SND_TYPE","type":"string"},{"name":"BWORK","type":"int"}],"name":"XXXSchema","type":"record"},"description":"Autogenerated by NiFi"}
As can be seen there is a property called "schemaText" that contains an object, I want to convert it to a string, so the 'only' thing I need to do is add quotes at the beginning and end of the property and escape the quotes inside.
Using the regular expression bellow (not that my regex knowledge is really low), I am able to do the first step:
({"schemaText":)(\{"fields":\[.*)(,"description.*)
Using the substitution
$1"$2"$3
gives the result:
{"schemaText":"{"fields":[{"name":"AX_SND_TYPE","type":"string"},{"name":"BWORK","type":"int"}],"name":"XXXSchema","type":"record"}","description":"Autogenerated by NiFi"}
But still remains to escape the quotes to get this:
{"schemaText":"{\"fields\":[{\"name\":\"AX_SND_TYPE\",\"type\":\"string\"},{\"name\":\"BWORK\",\"type\":\"int\"}],"name":"XXXSchema","type":"record"}","description":"Autogenerated by NiFi"}
That is have valid JSON format.
The question is: is there a way to escape the quotes inside $2 capture group in the same regular expression?
Thanks in advance.
The answer to your question is no, it's not possible. You're really trying to do two different, unrelated substitutions in a single regular expression. This is a feature that no regular expression engine supports.
Think about it: Your first requirement is for the engine to perform a substitution on the whole text (the quotes), and then, for your second requirement, the engine has to somehow backtrack and perform more substitutions on text which may or may not have already changed: e.g.: It would need to perform a new match on the already substituted text, which, depending on what the first substitution did, may not even exist anymore!
If, as you say, you already have an aproach that works, keep that. A single regular expression is simply not a good fit for what you are trying to do.
I'd recommend tackling this problem using code e.g. with vanilla JavaScript:
let json = '{"schemaText":{"fields":[{"name":"AX_SND_TYPE","type":"string"},{"name":"BWORK","type":"int"}],"name":"XXXSchema","type":"record"},"description":"Autogenerated by NiFi"}';
let obj = JSON.parse(json);
let schemaTextAsString = JSON.stringify(obj.schemaText)
obj.schemaText = schemaTextAsString
var result = JSON.stringify(obj)
You can see this working here.
Note that in your desired output you were not escaping the quotes in schemaText's name field, but this code does.
Finally whenever I use regular expressions I always think of this classic article "Regular Expressions: Now You Have Two Problems"!
Just for your information, you can actually match at every position where a substitution should occur, using an expression such as the following:
/({"schemaText":)|}(,"description")(.*)|([^"]*)"/g
The only issue, as others have mentioned, is that you want to do more than match; you want to perform a "conditional replacement" because there does not exist a single catch-all substitution that will cover all 3 cases you're dealing with (insert starting ", insert \ before quotes, and insert ending ").
You can in fact accomplish this with a single replace() call:
var test = "{\"schemaText\":{\"fields\":[{\"name\":\"AX_SND_TYPE\",\"type\":\"string\"},{\"name\":\"BWORK\",\"type\":\"int\"}],\"name\":\"XXXSchema\",\"type\":\"record\"},\"description\":\"Autogenerated by NiFi\"}";
window.alert(test.replace(/({"schemaText":)|}(,"description")(.*)|([^"]*)"/g, function(a,b,c,d,e){ return (b=="{\"schemaText\":"?b+"\"":(c==",\"description\""?"}\""+c+d:e+"\\\"")) })));
So it's technically "the same regex", but the substitution parameter uses an inline function as replacement rather than a static string.
I have the following text strings:
"Name":"John"}]
"Age":36
"Address":"ABC,PQR234[]/.,#ANYCHARACTERS"
"Gender":null
I need to get two groups (key value pair) from this such that the output would be only:
Key|Value
Name|John
Age|36
Address|ABC,PQR234[]/.,#ANYCHARACTERS
The requirement is to have a single regex to grab everything in the double quotes if the double quotes are present. If not, take the value without the quotes.
In our example above, 36 and null are the one without the quotes and they need to be captured as well.
I have tried a lot but have failed to do so.
UPDATE:
I don't know why I am getting down votes for this question. Yes this is JSON that I am trying to parse but there is a reason behind why I am doing this and not using any document parser.
I am supposed to use Talend for getting a dynamic JSON converted into Key Value Pair. What I mean by dynamic is the fields of the JSON can vary and hence I do not have a fixed schema and hence cannot use a document parser (which demands a fixed structure of JSON). I am devising a solution to get around this using Normalizer (on comma) and then extracting the key value pair which will be in double quotes using Regular Expressions. I tried many things on my own and since I am not an expert in Regular expressions, I have come here to get inputs.
If you know any better solution to this, I would be very happy to get your inputs.
How about this?
/"?([^\n"]*)"?:"?([^\n"]*)"?/
Explained in detail at:
https://regex101.com/r/UM0rl2/1/
I am trying to create a regex to validate usernames which should match the following :
Only one special char (._-) allowed and it must not be at the extremes of the string
The first character cannot be a number
All the other characters allowed are letters and numbers
The total length should be between 3 and 20 chars
This is for an HTML validation pattern, so sadly it must be one big regex.
So far this is what I've got:
^(?=(?![0-9])[A-Za-z0-9]+[._-]?[A-Za-z0-9]+).{3,20}
But the positive lookahead can be repeated more than one time allowing to be more than one special character which is not what I wanted. And I don't know how to correct that.
You should split your regex into two parts (not two Expressions!) to make your life easier:
First, match the format the username needs to have:
^[a-zA-Z][a-zA-Z0-9]*[._-]?[a-zA-Z0-9]+$
Now, we just need to validate the length constraint. In order to not mess around with the already found pattern, you can use a non-consuming match that only validates the number of characters (its literally a hack for creating an and pattern for your regular expression): (?=^.{3,20}$)
The regex will only try to match the valid format if the length constraint is matched. It is non-consuming, so after it is successful, the engine still is at the start of the string.
so, all together:
(?=^.{3,20}$)^[a-zA-Z][a-zA-Z0-9]*[._-]?[a-zA-Z0-9]+$
Debugger Demo
I think you need to use ? instead of +, so the special character is matched only once or not.
^(?=(?![0-9])?[A-Za-z0-9]?[._-]?[A-Za-z0-9]+).{3,20}