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First, we'll create the source code directory, json-to-csv.

Let's now get started making a Node script that we can use to convert a JSON file to CSV from the command line. I recommend Node v12 LTS which includes NPM 6. You'll need a version of Node.js that includes fs.promises and supports async/await and also have NPM installed. To get the most out of this article you should be familiar with the basics of Node.js, JavaScript, and async/await. At the end of the tutorial, I'll also show you how to use this instead of a custom converter. If you don't need to customize the conversion process, it's quicker to use a third-party package like json-2-csv. Writing a method to convert a JSON structure to CSV How to load a JSON file from the filesystem In this tutorial, we'll create a CLI script to convert an input JSON file to an output CSV file. However, the dominant data format in spreadsheet applications like Excel and Google Sheets is CSV, as this format is the tersest and easiest for users to understand and create.Ī common function that backend apps will need to perform, therefore, is the conversion of JSON to CSV. Now, let's use Jackson's CsvMapper to read our CSV file into a List of OrderLine objects.JSON has become the most popular way to pass data around on the modern web, with almost universal support between APIs and server applications. When we run this sample code, our example JSON document is converted to the expected CSV file.

writeValue(new File("src/main/resources/orderLines.csv"), jsonTree) Then, we create a CsvMapper with our CsvSchema, and finally, we write the jsonTree to our CSV file: CsvMapper csvMapper = new CsvMapper() JsonNode firstObject = jsonTree.elements().next() įirstObject.fieldNames().forEachRemaining(fieldName -> ) ĬsvSchema csvSchema = csvSchemaBuilder.build().withHeader() To do this, we create a CsvSchema Builder and set the column headers to match the JSON field names: Builder csvSchemaBuilder = CsvSchema.builder() This determines the column headers, types, and sequence of columns in the CSV file.

First, we use Jackson's ObjectMapper to read our example JSON document into a tree of JsonNode objects: JsonNode jsonTree = new ObjectMapper().readTree(new File("src/main/resources/orderLines.json"))