JFlat Utility 1.1.00

JFlat Utility

The JFlat Utility allows to parse JSON files into CSV or Flat map.

How to run the JFlat Utility inside Java

Add JFlat in the list of dependencies in your Maven pom.xml[1]:

<dependencies>
	<!-- [...] -->
	<dependency>
		<groupId>org.metricshub</groupId>
		<artifactId>jflat</artifactId>
		<version>1.1.00</version>
	</dependency>
</dependencies>

Instantiate it as follows:

import java.io.IOException;
import java.text.ParseException;
import java.util.Arrays;
import java.util.List;

import org.metricshub.jflat.JFlat;

public class Main {

	public static void main(String[] args) throws ParseException, IOException {

		// Action value to export to
		final int actionFlatMap = 1;
		final int actionToCsv = 2;
		final String defaultSeparator = ";";

		// Initialization
		final int action = actionToCsv;

		/*
		 * 
		   [
			  {
			    "array": [
			      {
			        "id": "1",
			        "value": "0"
			      },
			      {
			        "id": "2",
			        "value": "0"
			      },
			      {
			        "id": "3",
			        "value": "0"
			      }
			    ]
			  },
			  {
			    "array": [
			      {
			        "id": "1",
			        "value": "0"
			      },
			      {
			        "id": "2",
			        "value": "0"
			      },
			      {
			        "id": "3",
			        "value": "0"
			      }
			    ]
			  }
			]
		 * 
		 */
		final String json = "[{\"array\":[{\"id\":\"1\",\"value\":\"0\"},{\"id\":\"2\",\"value\":\"0\"},{\"id\":\"3\",\"value\":\"0\"}]},{\"array\":[{\"id\":\"1\",\"value\":\"0\"},{\"id\":\"2\",\"value\":\"0\"},{\"id\":\"3\",\"value\":\"0\"}]}]";
		final String jsonEntryKey = "/array";
		// properties to export into CSV
		final List<String> propertyList = Arrays.asList("id", "value");
		final String separator = defaultSeparator;
		final boolean removeNodes = false;

		// Parse the JSON with JFlat
		JFlat jsonFlat = new JFlat(json);

		jsonFlat.parse(removeNodes);

		// toCSV or flatMap?
		if (action == actionToCsv) {
			System.out.print(
					jsonFlat.toCSV(jsonEntryKey, propertyList.toArray(new String[propertyList.size()]), separator));
		} else if (action == actionFlatMap) {
			System.out.print(jsonFlat.getFlatTree());
		}

	}

}

Wildcard Support for Object Keys

When a JSON structure uses dynamic object keys (e.g. a map of items keyed by UID), use the * wildcard in the entry key path to expand all direct children of that object into individual CSV rows.

For example, given the following JSON:

{
  "members": {
    "abc123": { "id": 0, "name": "Drive 0", "type": { "default": "NVMe" } },
    "def456": { "id": 1, "name": "Drive 1", "type": { "default": "NVMe" } }
  }
}

Use * to iterate over all children of members:

JFlat jFlat = new JFlat(json);
jFlat.parse();

// List all entries under members
System.out.print(jFlat.toCSV("/members/*", null, ";"));
// Output:
// /members/abc123;
// /members/def456;

// Extract properties (including nested paths)
System.out.print(jFlat.toCSV("/members/*", new String[] { "id", "name", "type/default" }, ";"));
// Output:
// /members/abc123;0;Drive 0;NVMe;
// /members/def456;1;Drive 1;NVMe;

Escaping the Wildcard

If you have a JSON property literally named *, escape it with a backslash:

// Refers to the literal property "*" under members, not a wildcard
jFlat.toCSV("/members/\\*", new String[] { "name" }, ";");
jflat
Links:
  • [1] https://maven.apache.org/pom.html
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