Java try 将 JSON 文件或字符串转换为 CSV 文件会得到一个空的 CSV 文件

为什么不直接从Sheets API响应中写入(本例摘自Java Sheet API quick-start)

public static void main(String... args) throws IOException, GeneralSecurityException {
    // Build a new authorized API client service.
    final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
    final String spreadsheetId = "<SHEET_ID>";
    final String range = "<SHEET_RANGE>";
    Sheets service = new Sheets.Builder(HTTP_TRANSPORT, JSON_FACTORY, getCredentials(HTTP_TRANSPORT))
            .setApplicationName(APPLICATION_NAME)
            .build();
    ValueRange response = service.spreadsheets().values()
            .get(spreadsheetId, range)
            .execute();
    List<List<Object>> values = response.getValues();
    if (values == null || values.isEmpty()) {
        System.out.println("No data found.");
    } else {
        /* Create a new writer */
        PrintWriter writer = new PrintWriter("data.csv");
        for (List<Object> list : values) {
            /* Building the string */
            StringBuilder str = new StringBuilder();
            str.append(list.get(0).toString() + ",");
            str.append(list.get(1).toString() + "\n");
            writer.write(str.toString());
        }
        /* Closing the writer */
        writer.close();
    }
}

在任何情况下，如果正确读取JSON对象，机制都是完全相同的.

Updated

如果您想直接从JSON中读取，可以使用以下示例(使用GSON):

public class SheetResponse {
    private String range;
    private String majorDimensions; 
    private List<List<Object>> values;
}

public static void main(String... args) throws IOException, GeneralSecurityException {
    // Build a new authorized API client service.
    var gson = new Gson();
    var reader = new JsonReader(new FileReader("test.json"));
    SheetResponse sR = gson.fromJson(reader, SheetResponse.class);
    PrintWriter writer = new PrintWriter("data.csv");
    for (List<Object> list : sR.values) {
        /* Building the string */
        StringBuilder str = new StringBuilder();
        str.append(list.get(0).toString() + ",");
        str.append(list.get(1).toString() + "\n");
        writer.write(str.toString());
    }
    /* Closing the writer */
    writer.close();
}

Updated for the general case

public static void main(String... args) throws IOException, GeneralSecurityException {
    // Build a new authorized API client service.
    var gson = new Gson();
    var reader = new JsonReader(new FileReader("test.json"));
    SheetResponse sR = gson.fromJson(reader, SheetResponse.class);
    PrintWriter writer = new PrintWriter("data.csv");

    for (int i = 0; i < sR.values.size(); i++) {
        var valueRow = sR.values.get(i);
        StringBuilder str = new StringBuilder();
        for (int j = 0; j < valueRow.size(); j++) {
            if (j == valueRow.size() - 1) {
                str.append(valueRow.get(j).toString() + "\n");
            } else {
                str.append(valueRow.get(j).toString() + ",");
            }
        }
        writer.write(str.toString());
    }
    /* Closing the writer */
    writer.close();
}

Documentation

• PrintWriter
• StringBuilder