JSONをCSVに変換する

JSONをCSVに変換する

ファイル不正時などはいったん考慮せず、ロジックだけおぼえがき。

jsonToCsv.java

	/**
	 * JSONをCSVに変換する.
	 *
	 * @throws IOException
	 */
	public static void jsonToCsv() throws IOException {

		String json = "[{\"head1\":\"a\",\"head2\":\"b\",\"head3\":\"c\",\"head4\":\"d\",\"head5\":\"e\"},{\"head1\":\"1\",\"head2\":\"2\",\"head3\":\"3\",\"head4\":\"4\",\"head5\":\"5\"},{\"head1\":\"q\",\"head2\":\"qq\",\"head3\":\"qqq\",\"head4\":\"qqqq\",\"head5\":\"qqqqq\"}]";
		// 両サイドの[]を排除し、},{で区切る イメージは "head1":"1","head2":"2","head3":"3","head4":"4","head5":"5"
		List<String> trimJson = Arrays.asList(json.split("\\[")[1].split("\\]")[0].split("\\},\\{"));

		// 1レコード1mapに成形する
		Function<String, Map<String, String>> toMap = str -> {
			Map<String, String> map = new HashMap<>();
			for (String s : str.split(",")) {
				String[] keyValue = s.split(":");
				map.put(keyValue[0].split("\"")[1], keyValue[1].split("\"")[1]);
			}
			return map;
		};

		List<Map<String, String>> recordList = trimJson.stream()
				.map(String::trim)
				.map(v -> v.startsWith("\\{") ? v.split("\\{")[1] : v)
				.map(toMap)
				.collect(Collectors.toList());

		// csvファイルを作成、書き込む
		File csv = new File("csvファイルパス");
		csv.createNewFile();
		FileWriter filewriter = new FileWriter(csv);
		String header = String.join(",", recordList.get(0).keySet());
		String bodies = recordList.stream()
				.map(Map::values)
				.map(v -> String.join(",", v))
				.collect(Collectors.joining("\r\n"));
		filewriter.write(header + "\r\n");
		filewriter.write(bodies);
		filewriter.close();
	}