How to select one object in JSON array string using Java Regex?

Question

I have this String (please note that I must use this as string, not converted to JSON).

String cats = "[{'_id':'abxyz','image':'http://127.0.0.1/abxyz.png','name':'Tabby Cat'},{'_id':'xyzr2','image':'http://127.0.0.1/abxr2.png','name':'Calico Cat'},{'_id':'ghjkl','image':'http://127.0.0.1/ghjkl.png','name':'Persian Cat'},{'_id':'ojr12','image':'http://127.0.0.1/ojr12.png','name':'Angora Cat'}]";

or for better readability: (there is no white space between object)

String cats =
"[{'_id':'abxyz','image':'http://127.0.0.1/abxyz.png','name':'Tabby Cat'},\
{'_id':'xyzr2','image':'http://127.0.0.1/abxr2.png','name':'Calico Cat'},\
{'_id':'ghjkl','image':'http://127.0.0.1/ghjkl.png','name':'Persian Cat'},\
{'_id':'ojr12','image':'http://127.0.0.1/ojr12.png','name':'Angora Cat'}]";

I want to extract the Calico Cat object using regex. I tried to use

String pattern = "{\'_id\':\'xyzr2\'.*}"

Unfortunately, the selection expands from Calico Cat to Angora Cat:

{'_id':'xyzr2','image':'http://127.0.0.1/abxr2.png','name':'Calico Cat'},\
{'_id':'ghjkl','image':'http://127.0.0.1/ghjkl.png','name':'Persian Cat'},\
{'_id':'ojr12','image':'http://127.0.0.1/ojr12.png','name':'Angora Cat'}

What kind of regex pattern I need to isolate only the Calico Cat? Expected result:

{'_id':'xyzr2','image':'http://127.0.0.1/abxr2.png','name':'Calico Cat'}

"I want to extract the Calico Cat object using regex." Why don't you want to use a JSON parser? That's the natural approach to, y'know, parsing JSON... — Jon Skeet
– Jon Skeet, Commented Jun 8, 2016 at 10:17
I'm curious, what's the reason that you don't want to parse this? — Pieter De Bie
– Pieter De Bie, Commented Jun 8, 2016 at 10:26
That's the limitation imposed by the challenge, that's why. Also to enhance my RegEx understanding. — EdgarDrake
– EdgarDrake, Commented Jun 9, 2016 at 3:24

Community · Accepted Answer · 2017-05-23 11:52:32Z

1

You need to make it non-greedy to get smallest possible match

String pattern = "{\'_id\':\'xyzr2\'.*?}"

Regex explanation here.

Regular expression visualization

or use following regex

String pattern = "{\'_id\':\'xyzr2\'[^}]*}"

Regex explanation here.

Regular expression visualization

FYI : Always it's better to use json parser instead of hard coded regex, since the data is in valid json. Refer : How to parse JSON in Java

edited May 23, 2017 at 11:52

CommunityBot

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answered Jun 8, 2016 at 10:19

Pranav C Balan

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