Package org.djutils.data.json

Class JSONData

java.lang.Object

org.djutils.data.json.JSONData

public final class JSONData
extends Object

JSONData takes care of reading and writing of table data in JSON format. The reader and writer use a streaming API to avoid excessive memory use. The class can be used, e.g., as follows:

 DataTable dataTable = new ListDataTable("data", "dataTable", columns);
 Writer writer = new FileWriter("c:/data/data.json");
 JSONData.writeData(writer, dataTable);
 

The JSON document has the following structure:

 {
   "table": {
     "id": "tableId",
     "description": "table description",
     "class": "org.djutils.data.ListDataTable"",
     "columns": [
       {
         "nr": "0",
         "id": "time",
         "description": "time in [s]",
         "class": "org.djtils.vdouble.scalar.Time",
       },
       {
         "nr": "1",
         "id": "value",
         "description": "value [cm]",
         "class": "double",
       },
       {
         "nr": "2",
         "id": "comment",
         "description": "comment",
         "class": "java.lang.String",
       },
     ] 
   },
   "data": [
     [ { "0" : "2" }, { "1": "14.6" }, { "2" : "normal" } ],   
     [ { "0" : "4" }, { "1": "18.7" }, { "2" : "normal" } ],   
     [ { "0" : "6" }, { "1": "21.3" }, { "2" : "abnormal" } ]
   ]
 }
 

Copyright (c) 2020-2021 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://djutils.org. The DJUTILS project is distributed under a three-clause BSD-style license, which can be found at https://djutils.org/docs/license.html.

Author:

Alexander Verbraeck, Peter Knoppers, Wouter Schakel

Method Summary

Modifier and Type	Method	Description
static DataTable	readData(Reader reader)	Read the data from the csv-file into the data table.
static DataTable	readData(String filename)	Read the data from the csv-file into the data table.
static void	writeData(Writer writer, DataTable dataTable)	Write the data from the data table in JSON format.
static void	writeData(String filename, DataTable dataTable)	Write the data from the data table in JSON format.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

writeData

public static void writeData(Writer writer,
                             DataTable dataTable)
                      throws IOException,
                             TextSerializationException

Write the data from the data table in JSON format.

Parameters:

writer - Writer; the writer that writes the data, e.g. to a file

dataTable - DataTable; the data table to write

Throws:

IOException - on I/O error when writing the data

TextSerializationException - on unknown data type for serialization

writeData

public static void writeData(String filename,
                             DataTable dataTable)
                      throws IOException,
                             TextSerializationException

Write the data from the data table in JSON format.

Parameters:

filename - String; the file name to write the data to

dataTable - DataTable; the data table to write

Throws:

IOException - on I/O error when writing the data

TextSerializationException - on unknown data type for serialization

readData

public static DataTable readData(Reader reader)
                          throws IOException,
                                 TextSerializationException

Read the data from the csv-file into the data table. Use the metadata to reconstruct the data table.

Parameters:

reader - Reader; the reader that can read the data, e.g. from a file

Returns:

dataTable the data table reconstructed from the meta data and filled with the data

Throws:

IOException - on I/O error when reading the data

TextSerializationException - on unknown data type for serialization

readData

public static DataTable readData(String filename)
                          throws IOException,
                                 TextSerializationException

Read the data from the csv-file into the data table. Use the metadata to reconstruct the data table.

Parameters:

filename - String; the file name to read the data from

Returns:

dataTable the data table reconstructed from the meta data and filled with the data

Throws:

IOException - on I/O error when reading the data

TextSerializationException - on unknown data type for serialization