如何在 Java 中读取多行值 CSV 文件？

Question

Since a valid JSON file may contain only one JSON I intend to put multiple JSONs into a CSV file separated by a ";" and to read it using OpenCSV. (It's for putting those JSON data in file apart from the JUnit class to make it better readable.)

Is there a way to read multiple lines until the delimiter ";" occurs? Maybe it would be a good idea to enhance the JSON by an additional field _name which could be used as a key for a Map to read the JSON into!?? I tried it this way first to read into a List but it reads all lines into the list just eliminating the ";". I need a way to read until ";" occurs, store all lines read before into the Map<String, String> or better Map<String, JsonNode> and continue with the next.

    final ClassLoader classLoader = CrmServiceUT.class.getClassLoader();
    final File file = new File(classLoader.getResource("data/UpdatedDeal1.csv").getFile());
    final List<List<String>> records = new ArrayList<List<String>>();
    final CSVParser parser = new CSVParserBuilder().withSeparator(';').build();
    try (final BufferedReader br = Files.newBufferedReader(file.toPath(), StandardCharsets.UTF_8);
         final CSVReader csvReader = new CSVReaderBuilder(br).withCSVParser(parser).build()){
        String[] values = null;
                List<String> list = null;
        while ((values = csvReader.readNext()) != null) {
            if( !Stream.of(values).anyMatch(x -> x.contains(";")) ) {
                list = Arrays.asList(values);
            }
            if(list.contains(";")) {
                list.remove(";");
            }
                records.add(list);
        }
    } catch (CsvValidationException e) {
        e.printStackTrace();
    } catch (CsvException e) {
        e.printStackTrace();
    }

The JSON may be totally different with a few or a lot of lines:

{
  "_nodeName": "updatedDeal1",
  "results": [
    184896670
  ],
  "hasMore": false,
  "offset": 184896670
}
;
{
"_nodeName": "updatedDeal1",
"results": [
184896670
],
"hasMore": false,
"abcde": "xyz",
"offset": 184896670
}

With LHCHIN's answer I ended up in this solution to additionally handle the case that the delimiter (';') may be followed by the next JSON in one line:

@BeforeAll
public static void beforeAll() throws IOException {
    final ClassLoader classLoader = CrmServiceUT.class.getClassLoader();
    final File file = new File(classLoader.getResource("data/jsonsUT.csv").getFile());
    final StringBuilder sb = new StringBuilder();
    for (final String line : Files.readAllLines(file.toPath(), StandardCharsets.UTF_8)) {
        sb.append(line);
        if (line.endsWith(";")) {
            putJsonToMap(sb.substring(0, sb.length()-1));
            sb.delete(0, sb.length());
        }
    }
    putJsonToMap(sb.substring(0, sb.length()));
}

/**
 * Fills a map with JSON used throughout the unit tests.
 *
 * @param jsonStr       The JSON to be stored.
 * @throws IOException
 */
private static void putJsonToMap(final String jsonStr) throws IOException {
    final JsonNode node = mapper.readTree(jsonStr);
    jsons.put(node.get("_nodeName").asText(), node);
    ((ObjectNode) node).remove("_nodeName");
}

Answer 1

For your case, I cannot see any advantage to use opencsv , so why not just handle it by yourself!

Following example shows how to read a given CSV file line by line and put each line into a StringBuilder for concatenation, then once you find a line which ends with ; , add the content of StringBuilder to a list of String .

Code snippet

List<String> records = new ArrayList<>();
StringBuilder sb = new StringBuilder();
for (String line : Files.readAllLines(file.toPath(), StandardCharsets.UTF_8)) {
    sb.append(line);
    if (line.endsWith(";")) {
        records.add(sb.substring(0, sb.length()-1));
        sb.delete(0, sb.length());
    }
}

After that, each element in the List is a JSON string, you can access them directly for further manipulation.

Answer 2

You can read CSV file just like this and can get each row and column

BufferedReader csvReader;
csvReader = new BufferedReader(new FileReader(file.getPath())); // csv file path
while ((row = csvReader.readLine()) != null) {
String[] data = row.split(",");  // in data you have each column value for each row
}

Answer 3

我想，就去做吧。

json.replace('\n', '').replace(';','\n');