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Not able to download created excel using Java

Please check my code. There is no error. But still, I am not getting any excel downloaded. The console also shows no error and the sysout also shows the correct sizes of lists. 9 row data is coming from dao to this tpaAuthList. Please help.
#RequestMapping(value = "downloadTpaPreAuthExcel", method = RequestMethod.POST)
public void downloadTpaPreAuthExcel(#RequestParam("typevalue") String typevalue,
#RequestParam("idtypevalue") String idtypevalue, HttpServletRequest request,HttpServletResponse response, HttpSession session) {
Map<String, Object> map = new HashMap<String, Object>();
List<TpaPreAuthModel> tpaAuthList;
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-Disposition", "attachment; filename=TpaPreAuth.xls");
try {
tpaAuthList = tpaPreAuthService.getTpaPreAuthSearchDataForExcel(typevalue,idtypevalue);
System.out.println("tpaAuthList size in method-->"+tpaAuthList.size());
HSSFWorkbook workbook = new HSSFWorkbook();
HSSFSheet sheet = workbook.createSheet("DataSheet");
Map<String, Object[]> data = new LinkedHashMap<>();
data.put(String.valueOf(1), new Object[]{" TPA PRE AUTH LIST"});
data.put(String.valueOf(2), new Object[]{""});
data.put(String.valueOf(3), new Object[]{""});
int i = 5;
data.put("4", new Object[]{"Transaction ID", "Patient Name", "Hospital Name", "Pre Auth Date", "RGHS Card No", "Minutes Elapsed"});
for (TpaPreAuthModel listBean : tpaAuthList) {
data.put(String.valueOf(i), new Object[]{1,2,3,4,5,6});
i++;
}
System.out.println("For loop ended--");
Set<String> keyset = data.keySet();
int rownum = 0;
System.out.println("keyset size-->"+keyset.size());
for (String key : keyset) {
HSSFRow row = sheet.createRow(rownum++);
Object[] objArr = data.get(key);
int cellnum = 0;
for (Object obj : objArr) {
HSSFCell cell = row.createCell(cellnum++);
if (obj instanceof Date) {
cell.setCellValue((Date) obj);
} else if (obj instanceof Boolean) {
cell.setCellValue((Boolean) obj);
} else if (obj instanceof String) {
cell.setCellValue((String) obj);
} else if (obj instanceof Double) {
cell.setCellValue((Double) obj);
} else if (obj instanceof Long) {
cell.setCellValue((Long) obj);
}
}
}
System.out.println("Ket set for loop ended--");
OutputStream outputStream = response.getOutputStream();
System.out.println("Outstream--");
workbook.write(outputStream);
outputStream.flush();
outputStream.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
}

Close workbook before it become file. See https://poi.apache.org/apidocs/dev/org/apache/poi/hssf/usermodel/HSSFWorkbook.html#close--
For better
HSSFWorkbook workbook = null;
try {
workbook = ...
//....
} catch (IOException ex) {
//...
}finally {
workbook.close();
}

You could try this:
#RequestMapping(value = "downloadTpaPreAuthExcel", method = RequestMethod.GET)
public Callable<ResponseEntity<StreamingResponseBody>> downloadTpaPreAuthExcel(
#RequestParam("typevalue") String typevalue,
#RequestParam("idtypevalue") String idtypevalue
) {
return new Callable<ResponseEntity<StreamingResponseBody>>() {
#Override
public ResponseEntity<StreamingResponseBody> call() throws Exception {
return toResponseBody(new Supplier<Workbook>() {
#Override
public Workbook get() {
Map<String, Object> map = new HashMap<String, Object>();
List<TpaPreAuthModel> tpaAuthList;
try {
tpaAuthList = tpaPreAuthService.getTpaPreAuthSearchDataForExcel(typevalue, idtypevalue);
System.out.println("tpaAuthList size in method-->" + tpaAuthList.size());
HSSFWorkbook workbook = new HSSFWorkbook();
HSSFSheet sheet = workbook.createSheet("DataSheet");
Map<String, Object[]> data = new LinkedHashMap<>();
data.put(String.valueOf(1), new Object[] { " TPA PRE AUTH LIST" });
data.put(String.valueOf(2), new Object[] { "" });
data.put(String.valueOf(3), new Object[] { "" });
int i = 5;
data.put("4", new Object[] { "Transaction ID", "Patient Name", "Hospital Name",
"Pre Auth Date", "RGHS Card No", "Minutes Elapsed" });
for (TpaPreAuthModel listBean : tpaAuthList) {
data.put(String.valueOf(i), new Object[] { 1, 2, 3, 4, 5, 6 });
i++;
}
System.out.println("For loop ended--");
Set<String> keyset = data.keySet();
int rownum = 0;
System.out.println("keyset size-->" + keyset.size());
for (String key : keyset) {
HSSFRow row = sheet.createRow(rownum++);
Object[] objArr = data.get(key);
int cellnum = 0;
for (Object obj : objArr) {
HSSFCell cell = row.createCell(cellnum++);
if (obj instanceof Date) {
cell.setCellValue((Date) obj);
} else if (obj instanceof Boolean) {
cell.setCellValue((Boolean) obj);
} else if (obj instanceof String) {
cell.setCellValue((String) obj);
} else if (obj instanceof Double) {
cell.setCellValue((Double) obj);
} else if (obj instanceof Long) {
cell.setCellValue((Long) obj);
}
}
}
System.out.println("Ket set for loop ended--");
return workbook;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
}, "TpaPreAuth.xlsx");
}
};
}
private ResponseEntity<StreamingResponseBody> toResponseBody(Supplier<Workbook> workbookSupplier, String fileName) {
Workbook workbook = workbookSupplier.get();
return ResponseEntity.ok()
.header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName)
.contentType(MediaType.parseMediaType("application/vnd.ms-excel"))
.body(new StreamingResponseBody() {
#Override
public void writeTo(OutputStream outputStream) throws IOException {
if (workbook != null) {
try (Workbook workbookRef = workbook) {
workbook.write(outputStream);
if (workbook instanceof SXSSFWorkbook ) {
((SXSSFWorkbook) workbook).dispose();
}
} finally {
if (workbook instanceof SXSSFWorkbook ) {
((SXSSFWorkbook) workbook).dispose();
}
}
}
}
}
);
}

JSON flattener returning only last object from JSON to a flattened form

I have a JSON that looks like below,
{
"users": [
{
"displayName": "Sharad Dutta",
"givenName": "",
"surname": "",
"extension_user_type": "user",
"identities": [
{
"signInType": "emailAddress",
"issuerAssignedId": "kkr007#gmail.com"
}
],
"extension_timezone": "VET",
"extension_locale": "en-GB",
"extension_tenant": "EG12345"
},
{
"displayName": "Sharad Dutta",
"givenName": "",
"surname": "",
"extension_user_type": "user",
"identities": [
{
"signInType": "emailAddress",
"issuerAssignedId": "kkr007#gmail.com"
}
],
"extension_timezone": "VET",
"extension_locale": "en-GB",
"extension_tenant": "EG12345"
}
]
}
I have the above code and it is able to flatten the JSON like this,
{
"extension_timezone": "VET",
"extension_tenant": "EG12345",
"extension_locale": "en-GB",
"signInType": "userName",
"displayName": "Wayne Rooney",
"surname": "Rooney",
"givenName": "Wayne",
"issuerAssignedId": "pdhongade007",
"extension_user_type": "user"
}
But the code is returning only the last user in the "users" array of JSON. It is not returning the first user (essentially the last user only, no matter how many users are there) just the last one is coming out in flattened form from the "users" array.
public class TestConvertor {
static String userJsonAsString;
public static void main(String[] args) throws JSONException {
String userJsonFile = "C:\\Users\\Administrator\\Desktop\\jsonRes\\json_format_user_data_input_file.json";
try {
userJsonAsString = readFileAsAString(userJsonFile);
} catch (Exception e1) {
e1.printStackTrace();
}
JSONObject object = new JSONObject(userJsonAsString); // this is your input
Map<String, Object> flatKeyValue = new HashMap<String, Object>();
System.out.println("flatKeyValue : " + flatKeyValue);
readValues(object, flatKeyValue);
System.out.println(new JSONObject(flatKeyValue)); // this is flat
}
static void readValues(JSONObject object, Map<String, Object> json) throws JSONException {
for (Iterator it = object.keys(); it.hasNext(); ) {
String key = (String) it.next();
Object next = object.get(key);
readValue(json, key, next);
}
}
static void readValue(Map<String, Object> json, String key, Object next) throws JSONException {
if (next instanceof JSONArray) {
JSONArray array = (JSONArray) next;
for (int i = 0; i < array.length(); ++i) {
readValue(json, key, array.opt(i));
}
} else if (next instanceof JSONObject) {
readValues((JSONObject) next, json);
} else {
json.put(key, next);
}
}
private static String readFileAsAString(String inputJsonFile) throws Exception {
return new String(Files.readAllBytes(Paths.get(inputJsonFile)));
}
}
Please suggest where I am doing wrong or my code needs modification.

Please try the below approach, this will give you a comma separated format for both user and identifier (flat file per se),
public static void main(String[] args) throws JSONException, ParseException {
String userJsonFile = "path to your JSON";
final StringBuilder sBuild = new StringBuilder();
final StringBuilder sBuild2 = new StringBuilder();
try {
String userJsonAsString = convert your JSON to string and store in var;
} catch (Exception e1) {
e1.printStackTrace();
}
JSONParser jsonParser = new JSONParser();
JSONObject output = (JSONObject) jsonParser.parse(userJsonAsString);
try {
JSONArray docs = (JSONArray) output.get("users");
Iterator<Object> iterator = docs.iterator();
while (iterator.hasNext()) {
JSONObject userEleObj = (JSONObject)iterator.next();
JSONArray nestedIdArray = (JSONArray) userEleObj.get("identities");
Iterator<Object> nestIter = nestedIdArray.iterator();
while (nestIter.hasNext()) {
JSONObject identityEleObj = (JSONObject)nestIter.next();
identityEleObj.keySet().stream().forEach(key -> sBuild2.append(identityEleObj.get(key) + ","));
userEleObj.keySet().stream().forEach(key -> {
if (StringUtils.equals((CharSequence) key, "identities")) {
sBuild.append(sBuild2.toString());
sBuild2.replace(0, sBuild2.length(), "");
} else {
sBuild.append(userEleObj.get(key) + ",");
}
});
}
sBuild.replace(sBuild.lastIndexOf(","), sBuild.length(), "\n");
}
System.out.println(sBuild);
} catch (Exception e) {
e.printStackTrace();
}
}

Appending JSONObjects when writing to a file

I'm trying to append JSONObjects inside a JSONArray that is called Records .
The first time I save it it saves it this way that is ok
{
"Records": [
{
"travelTime": 2,
"totalDistance": 0,
"pace": 0,
"kCalBurned": 0,
"latlng": "[lat\/lng: (-32.1521234,-63.66412321)]"
}
]
}
But when I try to append again a new jsonobject inside Records, it creates a new JSONArray for it, and I just want to append a new object inside records
{
"Records": [
{
"travelTime": 2,
"totalDistance": 0,
"pace": 0,
"kCalBurned": 0,
"latlng": "[lat\/lng: (-31.6432292,-63.3667462)]"
}
]
}{
"Records": [
{
"travelTime": 1,
"totalDistance": 0,
"pace": 0,
"kCalBurned": 0,
"latlng": "[lat\/lng: (-31.9522431,-64.3461241)]"
}
]
}
This is the code I use to save the Records
private void writeJsonData(long travelTime,float totalDistance, float pace, float kCalBurned, LinkedList<LatLng> latlng){
String jsonStr = "";
JSONObject records = new JSONObject();
try {
records.put("travelTime", travelTime);
records.put("totalDistance", totalDistance);
records.put("pace", pace);
records.put("kCalBurned", kCalBurned);
records.put("latlng", latlng);
JSONArray jsonArray = new JSONArray();
jsonArray.put(records);
JSONObject recordsObj = new JSONObject();
recordsObj.put("Records", jsonArray);
jsonStr = recordsObj.toString();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String file_name = "records.json";
FileOutputStream fileOutputStream = null;
try {
fileOutputStream = new FileOutputStream(new File(mContext.getFilesDir(),file_name),true);
fileOutputStream.write(jsonStr.getBytes());
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}

You need a JSON parser so that you can locate the "Records" array inside the file and place the new data there. I used the "json simple" library (jar can be found here: https://code.google.com/archive/p/json-simple/downloads).
First you parse the file:
JSONParser parser = new JSONParser();
JSONObject records = null;
try {
records = (JSONObject) parser.parse(new FileReader("records.json"));
} catch (ParseException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
Then you locate the Records JSONArray. In there you want to append the new record:
JSONArray r = (JSONArray) records.get("Records");
Create the new record:
JSONObject NewObj = new JSONObject();
NewObj.put("travelTime", travelTime);
NewObj.put("totalDistance", totalDistance);
NewObj.put("pace", pace);
NewObj.put("kCalBurned", kCalBurned);
NewObj.put("latlng", latlng);
Add the new record to the "Records" JSONArray:
r.add(NewObj);
Write to file:
try (FileWriter file = new FileWriter("records.json")) {
file.write(records.toJSONString());
} catch (IOException ex) {
ex.printStackTrace();
}

Passing 2nd parameter to true in FileOutputStream constructor will
append jsonObject at the end of file.
To append it with JSON array inside Records object, you've to read the file first, append the new JSON object and write it back to file.
Use GSON library for conversion between java class & jSON. So you don't have to create JSON object manually each time by putting each key-pair.
Create a Java class to hold whole Records object
public class Record
{
#SerializedName("Records")
private List<Object> recordsList;
public Record()
{
this. recordsList = new ArrayList<>();
}
public List<Object> getRecordsList()
{
return recordsList;
}
}
Now create JAVA Model class to hold travel info
public class Travel {
private Integer travelTime;
private Integer totalDistance;
private Integer pace;
private Integer kCalBurned;
private LinkedList<LatLng> latlng;
public Integer getTravelTime() {
return travelTime;
}
public void setTravelTime(Integer travelTime) {
this.travelTime = travelTime;
}
public Integer getTotalDistance() {
return totalDistance;
}
public void setTotalDistance(Integer totalDistance) {
this.totalDistance = totalDistance;
}
public Integer getPace() {
return pace;
}
public void setPace(Integer pace) {
this.pace = pace;
}
public Integer getKCalBurned() {
return kCalBurned;
}
public void setKCalBurned(Integer kCalBurned) {
this.kCalBurned = kCalBurned;
}
public LinkedList<LatLng> getLatlng() {
return latlng;
}
public void setLatlng(LinkedList<LatLng> latlng) {
this.latlng = latlng;
}
}
Here is utility class with a function to append new JSON inside Records object. It will check if directory & file are created otherwise will create both.If file exist, it will read the file, append the new JSON object to list and write it back into the same file. You can change the directory & file name with yours.
Note: This class is written in Kotlin. Here is reference how to setup Android Studio for Kotlin
class Logger {
companion object {
private const val LOG_FILE_FOLDER = "Logs"
private const val LOG_FILE_NAME = "transaction"
private const val DATE_FORMAT = "yyyy-MM-dd"
private val logFileName: String
#SuppressLint("SimpleDateFormat")
get() {
var fileName = LOG_FILE_NAME
val dateFormat = SimpleDateFormat(DATE_FORMAT)
fileName += "_" + dateFormat.format(Date()) + ".json"
return fileName
}
fun logFile(json: Any) {
try {
val directoryPath = Environment.getExternalStorageDirectory().path + "/" + LOG_FILE_FOLDER
val loggingDirectoryPath = File(directoryPath)
var loggingFile = File("$directoryPath/$logFileName")
if (loggingDirectoryPath.mkdirs() || loggingDirectoryPath.isDirectory) {
var isFileReady = true
var isNewFile = false
if (!loggingFile.exists()) {
isFileReady = false
try {
loggingFile.createNewFile()
isNewFile = true
isFileReady = true
} catch (e: Exception) {
e.printStackTrace()
}
} else {
val lastFile = getLastFile(loggingFile.name, directoryPath)
loggingFile = File("$directoryPath/$lastFile")
val fileSize = getFileSize(loggingFile)
}
if (isFileReady) {
var jsonString: String? = null
if (!isNewFile) {
//Get already stored JsonObject
val stream = FileInputStream(loggingFile)
try {
val fileChannel = stream.channel
val mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size())
jsonString = Charset.defaultCharset().decode(mappedByteBuffer).toString()
} catch (e: Exception) {
e.printStackTrace()
} finally {
stream.close()
}
}
//Create record object
val record = if (!jsonString.isNullOrEmpty()) {
Gson().fromJson(jsonString, Record::class.java)
} else {
Record()
}
//Append the current json
record.recordList.add(json)
//create json to save
val jsonToSave = Gson().toJson(record)
val bufferedOutputStream: BufferedOutputStream
try {
bufferedOutputStream = BufferedOutputStream(FileOutputStream(loggingFile))
bufferedOutputStream.write(jsonToSave.toByteArray())
bufferedOutputStream.flush()
bufferedOutputStream.close()
} catch (e4: FileNotFoundException) {
e4.printStackTrace()
} catch (e: IOException) {
e.printStackTrace()
} finally {
System.gc()
}
}
}
} catch (ex: Exception) {
ex.printStackTrace()
}
}
}
}
At the end, you can log the file withlogFile method
Logger.Companion.logFile(travel);
Cheers :)

Java List to Excel Columns

Correct me where I'm going wrong.
I'm have written a program in Java which will get list of files from two different directories and make two (Java list) with the file names. I want to transfer the both the list (downloaded files list and Uploaded files list) to an excel.
What the result i'm getting is those list are transferred row wise. I want them in column wise.
Given below is the code:
public class F {
static List<String> downloadList = new ArrayList<>();
static List<String> dispatchList = new ArrayList<>();
public static class FileVisitor extends SimpleFileVisitor<Path> {
#Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
String name = file.toRealPath().getFileName().toString();
if (name.endsWith(".pdf") || name.endsWith(".zip")) {
downloadList.add(name);
}
if (name.endsWith(".xml")) {
dispatchList.add(name);
}
return FileVisitResult.CONTINUE;
}
}
public static void main(String[] args) throws IOException {
try {
Path downloadPath = Paths.get("E:\\report\\02_Download\\10252013");
Path dispatchPath = Paths.get("E:\\report\\01_Dispatch\\10252013");
FileVisitor visitor = new FileVisitor();
Files.walkFileTree(downloadPath, visitor);
Files.walkFileTree(downloadPath, EnumSet.of(FileVisitOption.FOLLOW_LINKS), 1, visitor);
Files.walkFileTree(dispatchPath, visitor);
Files.walkFileTree(dispatchPath, EnumSet.of(FileVisitOption.FOLLOW_LINKS), 1, visitor);
System.out.println("Download File List" + downloadList);
System.out.println("Dispatch File List" + dispatchList);
F f = new F();
f.UpDown(downloadList, dispatchList);
} catch (Exception ex) {
Logger.getLogger(F.class.getName()).log(Level.SEVERE, null, ex);
}
}
int rownum = 0;
int colnum = 0;
HSSFSheet firstSheet;
Collection<File> files;
HSSFWorkbook workbook;
File exactFile;
{
workbook = new HSSFWorkbook();
firstSheet = workbook.createSheet("10252013");
Row headerRow = firstSheet.createRow(rownum);
headerRow.setHeightInPoints(40);
}
public void UpDown(List<String> download, List<String> upload) throws Exception {
List<String> headerRow = new ArrayList<>();
headerRow.add("Downloaded");
headerRow.add("Uploaded");
List<List> recordToAdd = new ArrayList<>();
recordToAdd.add(headerRow);
recordToAdd.add(download);
recordToAdd.add(upload);
F f = new F();
f.CreateExcelFile(recordToAdd);
f.createExcelFile();
}
void createExcelFile() {
FileOutputStream fos = null;
try {
fos = new FileOutputStream(new File("E:\\report\\Download&Upload.xls"));
HSSFCellStyle hsfstyle = workbook.createCellStyle();
hsfstyle.setBorderBottom((short) 1);
hsfstyle.setFillBackgroundColor((short) 245);
workbook.write(fos);
} catch (Exception e) {
}
}
public void CreateExcelFile(List<List> l1) throws Exception {
try {
for (int j = 0; j < l1.size(); j++) {
Row row = firstSheet.createRow(rownum);
List<String> l2 = l1.get(j);
for (int k = 0; k < l2.size(); k++) {
Cell cell = row.createCell(k);
cell.setCellValue(l2.get(k));
}
rownum++;
}
} catch (Exception e) {
} finally {
}
}
}
(The purpose is to verify the files Downloaded and Uploaded for the given date)
Thanks.

If you want to access/build the worksheet in columns instead of rows, you need to change the worksheet accessing code.
Snipped out from your existing code, here are the key functions:
Row row = firstSheet.createRow( rowNum);
Cell cell = row.createCell( colNum);
cell.setCellValue( value);
You need to rearrange those loops to output your data in a column-wise fashion.

Thanks for the suggestions.. I have modified my program and uploaded with the solution.
public class F {
static List<String> downloadList = new ArrayList<>();
static List<String> dispatchList = new ArrayList<>();
public static class FileVisitor extends SimpleFileVisitor<Path> {
#Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
String name = file.toRealPath().getFileName().toString();
if (name.endsWith(".pdf") || name.endsWith(".zip")) {
downloadList.add(name);
}
if (name.endsWith(".xml")) {
dispatchList.add(name);
}
return FileVisitResult.CONTINUE;
}
}
public static void main(String[] args) throws IOException {
try {
Path downloadPath = Paths.get("E:\\Download\\10292013");
Path dispatchPath = Paths.get("E:\\Dispatch\\10292013");
FileVisitor visitor = new FileVisitor();
Files.walkFileTree(downloadPath, visitor);
Files.walkFileTree(downloadPath, EnumSet.of(FileVisitOption.FOLLOW_LINKS), 1, visitor);
Files.walkFileTree(dispatchPath, visitor);
Files.walkFileTree(dispatchPath, EnumSet.of(FileVisitOption.FOLLOW_LINKS), 1, visitor);
/* List all files*/
System.out.println("Download File List" + downloadList);
System.out.println("Dispatch File List" + dispatchList);
F f = new F();
f.UpDown(downloadList, dispatchList);
} catch (Exception ex) {
Logger.getLogger(F.class.getName()).log(Level.SEVERE, null, ex);
}
}
int rownum = 0;
int colnum = 0;
HSSFSheet firstSheet;
Collection<File> files;
HSSFWorkbook workbook;
File exactFile;
{
workbook = new HSSFWorkbook();
firstSheet = workbook.createSheet("10292013");
Row headerRow = firstSheet.createRow(rownum);
headerRow.setHeightInPoints(40);
}
public void UpDown(List<String> download, List<String> upload) throws Exception {
List<String> headerRow = new ArrayList<String>();
headerRow.add("Downloaded");
headerRow.add("Uploaded");
List<List<String>> recordToAdd = new ArrayList<List<String>>();
recordToAdd.add(headerRow);
recordToAdd.add(download);
recordToAdd.add(upload);
CreateExcelFile(headerRow, download, upload);
createExcelFile();
}
void createExcelFile() {
FileOutputStream fos = null;
try {
fos = new FileOutputStream(new File("E:\\report\\Download&Upload.xls"));
HSSFCellStyle hsfstyle = workbook.createCellStyle();
hsfstyle.setBorderBottom((short) 1);
hsfstyle.setFillBackgroundColor((short) 245);
workbook.write(fos);
} catch (Exception e) {
}
}
public void CreateExcelFile(List<String> headers, List<String> down, List<String> up) throws Exception {
try {
Row row = firstSheet.createRow((short)(rownum++));
for(int i = 0;i < headers.size();i++) {
Cell cell = row.createCell(i);
cell.setCellValue(headers.get(i));
}
for (int j = 0; j < down.size(); j++) {
row = firstSheet.createRow((short)(rownum++));
Cell cell = row.createCell(0);
cell.setCellValue(down.get(j));
if(up.size() > j) {
cell = row.createCell(1);
cell.setCellValue(up.get(j));
}
}
} catch (Exception e) {
} finally {
}
}
}

How to serialize object to CSV file?

I want to write a Object into CSV file.
For XML we have XStream like this
So if i want to convert object to CSV do we have any such library ?
EDIT:
I want to pass my list of Bean to a method which should write all the fields of bean to CSV.

First, serialization is writing the object to a file 'as it is'. AFAIK, you cannot choose file formats and all. The serialized object (in a file) has its own 'file format'
If you want to write the contents of an object (or a list of objects) to a CSV file, you can do it yourself, it should not be complex.
Looks like Java CSV Library can do this, but I have not tried this myself.
EDIT: See following sample. This is by no way foolproof, but you can build on this.
//European countries use ";" as
//CSV separator because "," is their digit separator
private static final String CSV_SEPARATOR = ",";
private static void writeToCSV(ArrayList<Product> productList)
{
try
{
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("products.csv"), "UTF-8"));
for (Product product : productList)
{
StringBuffer oneLine = new StringBuffer();
oneLine.append(product.getId() <=0 ? "" : product.getId());
oneLine.append(CSV_SEPARATOR);
oneLine.append(product.getName().trim().length() == 0? "" : product.getName());
oneLine.append(CSV_SEPARATOR);
oneLine.append(product.getCostPrice() < 0 ? "" : product.getCostPrice());
oneLine.append(CSV_SEPARATOR);
oneLine.append(product.isVatApplicable() ? "Yes" : "No");
bw.write(oneLine.toString());
bw.newLine();
}
bw.flush();
bw.close();
}
catch (UnsupportedEncodingException e) {}
catch (FileNotFoundException e){}
catch (IOException e){}
}
This is product (getters and setters hidden for readability):
class Product
{
private long id;
private String name;
private double costPrice;
private boolean vatApplicable;
}
And this is how I tested:
public static void main(String[] args)
{
ArrayList<Product> productList = new ArrayList<Product>();
productList.add(new Product(1, "Pen", 2.00, false));
productList.add(new Product(2, "TV", 300, true));
productList.add(new Product(3, "iPhone", 500, true));
writeToCSV(productList);
}
Hope this helps.
Cheers.

For easy CSV access, there is a library called OpenCSV. It really ease access to CSV file content.
EDIT
According to your update, I consider all previous replies as incorrect (due to their low-levelness). You can then go a completely diffferent way, the hibernate way, in fact !
By using the CsvJdbc driver, you can load your CSV files as JDBC data source, and then directly map your beans to this datasource.
I would have talked to you about CSVObjects, but as the site seems broken, I fear the lib is unavailable nowadays.

Two options I just ran into:
http://sojo.sourceforge.net/
http://supercsv.sourceforge.net/

It would be interesting to have a csv serializer as it would take up the minimal space compared to other serializing method.
The closest support for java object to csv is stringutils provided by spring utils project
arrayToCommaDelimitedString(Object[] arr) but it is far from being a serializer.
Here is a simple utility which uses reflection to serialize value objects
public class CSVWriter
{
private static String produceCsvData(Object[] data) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException
{
if(data.length==0)
{
return "";
}
Class classType = data[0].getClass();
StringBuilder builder = new StringBuilder();
Method[] methods = classType.getDeclaredMethods();
for(Method m : methods)
{
if(m.getParameterTypes().length==0)
{
if(m.getName().startsWith("get"))
{
builder.append(m.getName().substring(3)).append(',');
}
else if(m.getName().startsWith("is"))
{
builder.append(m.getName().substring(2)).append(',');
}
}
}
builder.deleteCharAt(builder.length()-1);
builder.append('\n');
for(Object d : data)
{
for(Method m : methods)
{
if(m.getParameterTypes().length==0)
{
if(m.getName().startsWith("get") || m.getName().startsWith("is"))
{
System.out.println(m.invoke(d).toString());
builder.append(m.invoke(d).toString()).append(',');
}
}
}
builder.append('\n');
}
builder.deleteCharAt(builder.length()-1);
return builder.toString();
}
public static boolean generateCSV(File csvFileName,Object[] data)
{
FileWriter fw = null;
try
{
fw = new FileWriter(csvFileName);
if(!csvFileName.exists())
csvFileName.createNewFile();
fw.write(produceCsvData(data));
fw.flush();
}
catch(Exception e)
{
System.out.println("Error while generating csv from data. Error message : " + e.getMessage());
e.printStackTrace();
return false;
}
finally
{
if(fw!=null)
{
try
{
fw.close();
}
catch(Exception e)
{
}
fw=null;
}
}
return true;
}
}
Here is an example value object
public class Product {
private String name;
private double price;
private int identifier;
private boolean isVatApplicable;
public Product(String name, double price, int identifier,
boolean isVatApplicable) {
super();
this.name = name;
this.price = price;
this.identifier = identifier;
this.isVatApplicable = isVatApplicable;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(long price) {
this.price = price;
}
public int getIdentifier() {
return identifier;
}
public void setIdentifier(int identifier) {
this.identifier = identifier;
}
public boolean isVatApplicable() {
return isVatApplicable;
}
public void setVatApplicable(boolean isVatApplicable) {
this.isVatApplicable = isVatApplicable;
}
}
and the code to run the util
public class TestCSV
{
public static void main(String... a)
{
Product[] list = new Product[5];
list[0] = new Product("dvd", 24.99, 967, true);
list[1] = new Product("pen", 4.99, 162, false);
list[2] = new Product("ipad", 624.99, 234, true);
list[3] = new Product("crayons", 4.99,127, false);
list[4] = new Product("laptop", 1444.99, 997, true);
CSVWriter.generateCSV(new File("C:\\products.csv"),list);
}
}
Output:
Name VatApplicable Price Identifier
dvd true 24.99 967
pen false 4.99 162
ipad true 624.99 234
crayons false 4.99 127
laptop true 1444.99 997

I wrote a simple class that uses OpenCSV and has two static public methods.
static public File toCSVFile(Object object, String path, String name) {
File pathFile = new File(path);
pathFile.mkdirs();
File returnFile = new File(path + name);
try {
CSVWriter writer = new CSVWriter(new FileWriter(returnFile));
writer.writeNext(new String[]{"Member Name in Code", "Stored Value", "Type of Value"});
for (Field field : object.getClass().getDeclaredFields()) {
writer.writeNext(new String[]{field.getName(), field.get(object).toString(), field.getType().getName()});
}
writer.flush();
writer.close();
return returnFile;
} catch (IOException e) {
Log.e("EasyStorage", "Easy Storage toCSVFile failed.", e);
return null;
} catch (IllegalAccessException e) {
Log.e("EasyStorage", "Easy Storage toCSVFile failed.", e);
return null;
}
}
static public void fromCSVFile(Object object, File file) {
try {
CSVReader reader = new CSVReader(new FileReader(file));
String[] nextLine = reader.readNext(); // Ignore the first line.
while ((nextLine = reader.readNext()) != null) {
if (nextLine.length >= 2) {
try {
Field field = object.getClass().getDeclaredField(nextLine[0]);
Class<?> rClass = field.getType();
if (rClass == String.class) {
field.set(object, nextLine[1]);
} else if (rClass == int.class) {
field.set(object, Integer.parseInt(nextLine[1]));
} else if (rClass == boolean.class) {
field.set(object, Boolean.parseBoolean(nextLine[1]));
} else if (rClass == float.class) {
field.set(object, Float.parseFloat(nextLine[1]));
} else if (rClass == long.class) {
field.set(object, Long.parseLong(nextLine[1]));
} else if (rClass == short.class) {
field.set(object, Short.parseShort(nextLine[1]));
} else if (rClass == double.class) {
field.set(object, Double.parseDouble(nextLine[1]));
} else if (rClass == byte.class) {
field.set(object, Byte.parseByte(nextLine[1]));
} else if (rClass == char.class) {
field.set(object, nextLine[1].charAt(0));
} else {
Log.e("EasyStorage", "Easy Storage doesn't yet support extracting " + rClass.getSimpleName() + " from CSV files.");
}
} catch (NoSuchFieldException e) {
Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
} catch (IllegalAccessException e) {
Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
}
} // Close if (nextLine.length >= 2)
} // Close while ((nextLine = reader.readNext()) != null)
} catch (FileNotFoundException e) {
Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
} catch (IOException e) {
Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
} catch (IllegalArgumentException e) {
Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
}
}
I think with some simple recursion these methods could be modified to handle any Java object, but for me this was adequate.

Though its very late reply, I have faced this problem of exporting java entites to CSV, EXCEL etc in various projects, Where we need to provide export feature on UI.
I have created my own light weight framework. It works with any Java Beans, You just need to add annotations on fields you want to export to CSV, Excel etc.
Link: https://github.com/abhisoni96/dev-tools

Worth mentioning that the handlebar library https://github.com/jknack/handlebars.java can trivialize many transformation tasks include toCSV.

You can use gererics to work for any class
public class FileUtils<T> {
public String createReport(String filePath, List<T> t) {
if (t.isEmpty()) {
return null;
}
List<String> reportData = new ArrayList<String>();
addDataToReport(t.get(0), reportData, 0);
for (T k : t) {
addDataToReport(k, reportData, 1);
}
return !dumpReport(filePath, reportData) ? null : filePath;
}
public static Boolean dumpReport(String filePath, List<String> lines) {
Boolean isFileCreated = false;
String[] dirs = filePath.split(File.separator);
String baseDir = "";
for (int i = 0; i < dirs.length - 1; i++) {
baseDir += " " + dirs[i];
}
baseDir = baseDir.replace(" ", "/");
File base = new File(baseDir);
base.mkdirs();
File file = new File(filePath);
try {
if (!file.exists())
file.createNewFile();
} catch (Exception e) {
e.printStackTrace();
return isFileCreated;
}
try (BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(new FileOutputStream(file), System.getProperty("file.encoding")))) {
for (String line : lines) {
writer.write(line + System.lineSeparator());
}
} catch (IOException e) {
e.printStackTrace();
return false;
}
return true;
}
void addDataToReport(T t, List<String> reportData, int index) {
String[] jsonObjectAsArray = new Gson().toJson(t).replace("{", "").replace("}", "").split(",\"");
StringBuilder row = new StringBuilder();
for (int i = 0; i < jsonObjectAsArray.length; i++) {
String str = jsonObjectAsArray[i];
str = str.replaceFirst(":", "_").split("_")[index];
if (i == 0) {
if (str != null) {
row.append(str.replace("\"", ""));
} else {
row.append("N/A");
}
} else {
if (str != null) {
row.append(", " + str.replace("\"", ""));
} else {
row.append(", N/A");
}
}
}
reportData.add(row.toString());
}