Question 1

data.json vs Cheshire for Clojure JSON parsing

Accepted Answer

data.json is a pure Clojure library with no dependencies, ideal for strict compliance and simplicity. Cheshire wraps the Jackson Java library, offering higher performance and more features like JSON Schema support, but adds an external dependency. Choose data.json for lightweight projects and Cheshire for speed-critical applications.

Question 2

How to handle custom date formats with data.json

Accepted Answer

Use the :date-formatter option in json/write-str to specify a java.time.DateTimeFormatter for custom formats. For reading, you can use :value-fn to parse date strings into Clojure data structures, as demonstrated in the README with java.sql.Date examples.

Question 3

Does data.json support JSON streaming for large files

Accepted Answer

Yes, data.json supports reading from java.io.Reader with json/read and writing to java.io.Writer with json/write, allowing efficient stream processing without loading entire files into memory. This is highlighted in the README's stream support section.

Question 4

How to convert Clojure keywords to JSON strings in data.json

Accepted Answer

Use the :key-fn option with a function like name during writing. For example, (json/write-str {:a 1} :key-fn name) converts keywords to strings. The README shows similar examples for key transformation.

Question 5

Is data.json thread-safe for concurrent use

Accepted Answer

Yes, data.json's functions are pure and immutable, making them thread-safe for concurrent parsing and generation. However, when using external streams like java.io.Reader, you need to manage thread-safety at the stream level.

Question 6

What happens if I try to parse invalid JSON with data.json

Accepted Answer

data.json throws exceptions for invalid JSON, such as malformed numbers or missing object entries, with improved error messages in recent versions like 2.5.2 for chars < 32. It strictly enforces JSON spec compliance to prevent silent failures.

data.json

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