Java - Write hashmap to a csv file
Something like this should do the trick:
String eol = System.getProperty("line.separator");
try (Writer writer = new FileWriter("somefile.csv")) {
for (Map.Entry<String, String> entry : myHashMap.entrySet()) {
writer.append(entry.getKey())
.append(',')
.append(entry.getValue())
.append(eol);
}
} catch (IOException ex) {
ex.printStackTrace(System.err);
}
Using the Jackson API, Map or List of Map could be written in CSV file. See complete example here
/**
* @param listOfMap
* @param writer
* @throws IOException
*/
public static void csvWriter(List<HashMap<String, String>> listOfMap, Writer writer) throws IOException {
CsvSchema schema = null;
CsvSchema.Builder schemaBuilder = CsvSchema.builder();
if (listOfMap != null && !listOfMap.isEmpty()) {
for (String col : listOfMap.get(0).keySet()) {
schemaBuilder.addColumn(col);
}
schema = schemaBuilder.build().withLineSeparator(System.lineSeparator()).withHeader();
}
CsvMapper mapper = new CsvMapper();
mapper.writer(schema).writeValues(writer).writeAll(listOfMap);
writer.flush();
}
As your question is asking how to do this using Super CSV, I thought I'd chime in (as a maintainer of the project).
I initially thought you could just iterate over the map's entry set using CsvBeanWriter
and a name mapping array of "key", "value"
, but this doesn't work because HashMap
's internal implementation doesn't allow reflection to get the key/value.
So your only option is to use CsvListWriter
as follows. At least this way you don't have to worry about escaping CSV (every other example here just joins with commas...aaarrggh!):
@Test
public void writeHashMapToCsv() throws Exception {
Map<String, String> map = new HashMap<>();
map.put("abc", "aabbcc");
map.put("def", "ddeeff");
StringWriter output = new StringWriter();
try (ICsvListWriter listWriter = new CsvListWriter(output,
CsvPreference.STANDARD_PREFERENCE)){
for (Map.Entry<String, String> entry : map.entrySet()){
listWriter.write(entry.getKey(), entry.getValue());
}
}
System.out.println(output);
}
Output:
abc,aabbcc
def,ddeeff
Map<String, String> csvMap = new TreeMap<>();
csvMap.put("Hotel Name", hotelDetails.getHotelName());
csvMap.put("Hotel Classification", hotelDetails.getClassOfHotel());
csvMap.put("Number of Rooms", hotelDetails.getNumberOfRooms());
csvMap.put("Hotel Address", hotelDetails.getAddress());
// specified by filepath
File file = new File(fileLocation + hotelDetails.getHotelName() + ".csv");
// create FileWriter object with file as parameter
FileWriter outputfile = new FileWriter(file);
String[] header = csvMap.keySet().toArray(new String[csvMap.size()]);
String[] dataSet = csvMap.values().toArray(new String[csvMap.size()]);
// create CSVWriter object filewriter object as parameter
CSVWriter writer = new CSVWriter(outputfile);
// adding data to csv
writer.writeNext(header);
writer.writeNext(dataSet);
// closing writer connection
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}