Design Patterns

JSON To CSV Converter

This is a modified version of json-to-csv project.

This code can be used for generating a flat CSV file from a list of JSON Objects. The JSONFlattener will create list of key-value pairs for the generated JSON. The CSVWriter would write the key value pairs to the specified file.

Usage:

1 - Using a JSON String:

JSON string:

{
	"firstName": "Brahim",
	"lastName": "Arkni"
}

JAVA code:

/*
 * Parse a JSON String and convert it to CSV
 */
List<Map<String, String>> flatJson = JSONFlattener.parseJson(jsonString);
// Using the default separator ','
// If you want to use an other separator like ';' or '\t' use
// CSVWriter.getCSV(flatJSON, separator) method
CSVWriter.writeToFile(CSVWriter.getCSV(flatJson), "files/sample_string.csv");

CSV output:

lastName,firstname
Arkni,Brahim

2 - Using a JSON file:

JSON file:

considering the file simple.json in /files directory, contains the following JSON

[
    {
        "studentName": "Foo",
        "Age": "12",
        "subjects": [
            {
                "name": "English",
                "marks": "40"
            },
            {
                "name": "History",
                "marks": "50"
            }
        ]
    },
    {
        "studentName": "Bar",
        "Age": "12",
        "subjects": [
            {
                "name": "English",
                "marks": "40"
            },
            {
                "name": "History",
                "marks": "50"
            },
            {
                "name": "Science",
                "marks": "40"
            }
        ]
    },
    {
        "studentName": "Baz",
        "Age": "12",
        "subjects": []
    }
]

JAVA code:

/*
 *  Parse a JSON File and convert it to CSV
 */
// There is 2 methods to parse the JSON file
// 1- JSONFlattener#parseJson(File file):
//    This will use the default encoding UTF-8 to parse the given file.
// 2- JSONFlattener#parseJson(File file, String encoding):
//    This will parse the file using the specified character encoding.
flatJson = JSONFlattener.parseJson(new File("files/simple.json"), "UTF-8");
// Using ';' as separator
CSVWriter.writeToFile(CSVWriter.getCSV(flatJson, ";"), "files/sample_file.csv");

CSV output (see /files/sample_file.csv file):

Age;subjects[1].marks;subjects[1].name;subjects[2].marks;subjects[2].name;studentName;subjects[3].marks;subjects[3].name
12;40;English;50;History;Foo;;
12;40;English;50;History;Bar;40;Science
12;;;;;Baz;;

3 - Using a JSON returned from a URL:

JAVA code:

/*
 *  Parse JSON from URL and convert it to CSV
 */
// There is 2 methods to parse a JSON returned from a URI
// 1- JSONFlattener#parseJson(URI uri):
//    This will use the default encoding UTF-8 to parse the JSON returned from the given uri.
// 2- JSONFlattener#parseJson(URI uri, String encoding):
//    This will parse the JSON returned from the uri using the specified character encoding.
flatJson = JSONFlattener.parseJson(new URI("http://echo.jsontest.com/firstname/Brahim/lastName/Arkni"));
// Using '\t' as separator
CSVWriter.writeToFile(CSVWriter.getCSV(flatJson, "\t"), "files/sample_uri.csv");

JSON:

for this example, I used the web service echo.jsontest.com to echo a JSON object like the following

{
	"firstName": "Brahim",
	"lastName": "Arkni"
}

CSV output (see /files/sample_uri.csv file):

lastName	firstname
Arkni		Brahim

N.B:

The column names would dynamically be generated based on the keys in the JSON object.
The order of the JSON keys will not preserved during JSON conversion to CSV, See this StackOverFlow question for more information.

The sample output files can be seen here.

Licence

See the LICENCE file.

	public class Main {

	public static void main(String[] args) throws Exception {
	/*
	* Parse a JSON String and convert it to CSV
	*/
	List<Map<String, String>> flatJson = JSONFlattener.parseJson(jsonString());
	// Using the default separator ','
	CSVWriter.writeToFile(CSVWriter.getCSV(flatJson), "files/sample_string.csv");

	/*
	* Parse a JSON File and convert it to CSV
	*/
	flatJson = JSONFlattener.parseJson(new File("files/simple.json"), "UTF-8");
	// Using ';' as separator
	CSVWriter.writeToFile(CSVWriter.getCSV(flatJson, ";"), "files/sample_file.csv");

	/*
	* Parse JSON from URL and convert it to CSV
	*/
	flatJson = JSONFlattener.parseJson(new URI("http://echo.jsontest.com/firstname/Brahim/lastName/Arkni"));
	// Using '\t' as separator
	CSVWriter.writeToFile(CSVWriter.getCSV(flatJson, "\t"), "files/sample_uri.csv");

	/*
	* Parse a Large JSON File and convert it to CSV
	*/
	flatJson = JSONFlattener.parseJson(new File("files/sample_large.json"), "UTF-8");
	// Using ';' as separator
	Set<String> header = CSVWriter.collectOrderedHeaders(flatJson);
	// the intention is generate a csv file with specific headers - not all
	CSVWriter.writeLargeFile(flatJson, ";", "files/sample_largeFile.csv", header);
	}

	private static String jsonString() {
	return "[" +
	" {" +
	" \"studentName\": \"Foo\"," +
	" \"Age\": \"12\"," +
	" \"subjects\": [" +
	" {" +
	" \"name\": \"English\"," +
	" \"marks\": \"40\"" +
	" }," +
	" {" +
	" \"name\": \"History\"," +
	" \"marks\": \"50\"" +
	" }" +
	" ]" +
	" }" +
	"]";
	}
	}

arkni / json-to-csv Goto Github PK

json-to-csv's Introduction

JSON To CSV Converter

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N.B:

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