Clojure parse JSON objects and extract specific key

Question

Given I have a json file with the contents:

[
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  },
  {
    "email": "[email protected]"
  }
]

How can I parse this file and get the value for each email tag as I need to perform operations using the values.

Example:

Retrieve list of emails

([email protected], [email protected]...)

for each element in the list pass its value to a function. I understand how to pass it to a function, and have come across the get-in function but im not fully sure how to use it in this context.

Optionally, if possible I wish for the file to be stored

[email protected]
[email protected]
...

which will be more practical. I know how to write to a file and such but im not sure how to extract the email data.

Dax Fohl · Accepted Answer · 2015-07-27 11:18:44Z

3

slurp reads the file into a string, then use a JSON parser (e.g. cheshire or data.json) to make it into a vector. If you want to use the second file format, then look at line-seq or split-lines

answered Jul 27, 2015 at 11:18

Dax Fohl

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6 Comments

Chris Edwards Over a year ago

I understand how to get the string from a file, I don't understand how to extract each email value from such string

Dax Fohl Over a year ago

@ChrisEdwards use the JSON parser, then if you're wanting to do something with each of them then use doseq to do so. e.g. (doseq [record (cheshire/parse-string (slurp filename))] (my-function (:email record)))

Chris Edwards Over a year ago

do you want to post this as an answer so others can find it easier?

Dax Fohl Over a year ago

@ChrisEdwards I'm still not sure which part you were struggling with. Parsing, iterating through the sequence, or getting the email from the record?

Chris Edwards Over a year ago

@iterating through the sequence was my issue

|

Frank C. · Accepted Answer · 2015-07-27 12:23:12Z

2

Chris

You can read/parse the file as Dax pointed out and then, to address the other part of your question, once the maps are in a vector:

(def emails (map :email (json/read-str (slurp fully-qualified-file))))

will extract each each email into a sequence. You can then use something like the following to store the emails where each is a 'row' in the resulting file:

(spit fully-qualified-result-file (interpose "\n" emails))

answered Jul 27, 2015 at 12:23

Frank C.

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