I am trying to learn how to use try with resources. First I tried to put java.io.File myFile = new java.io.File(filename) in the resource parenthesis, but netbeans told me that it is not autoclosable. Am I properly handling this exception? I was under the impression that the Exception would be generated in the line where I define the file class object.
//This method writes to a csv or txt file, specify full filepath (including
//extension) Each value will be on a new line
public void writeFile(String filename)
{
java.io.File myFile = new java.io.File(filename);
try(java.io.PrintWriter outfile = new java.io.PrintWriter(myFile))
{
for (int i = 0; i < size; i++)
{
//print all used elements line by line
outfile.println(Integer.toString(this.getElement(i)));
}
} catch (FileNotFoundException fileNotFoundException)
{
//print error
}
}//end writeFile(String)----------------------------------------------------
Related
An attempt was made to implement file downloads through the SpringBoot MVC structure. There is no error, it says it has run normally, but the download does not proceed.
All information about the file is entered correctly, and also the path and name of the file are entered correctly.
I'd like to know why the download doesn't proceed even though there's no error.
#RestController
public class Controller {
#PostMapping("/fileDownload")
public void fileDownload(#RequestBody BoardFileDTO dto,HttpServletRequest request,HttpServletResponse response) throws UnsupportedEncodingException {
//File contains all stored paths, names, and extensions
Path fileNamePath = Paths.get(Directory + dto.getFile_save_name()).toAbsolutePath();
String filename = dto.getFile_save_name(); //The name of the saved file
String downname = dto.getFile_name(); //The name of the file to be saved
if (filename == null || "".equals(filename)) {
filename = downname;
}
try {
String browser = request.getHeader("User-Agent");
//File Encoding
if (browser.contains("MSIE") || browser.contains("Trident")
|| browser.contains("Chrome")) {
filename = URLEncoder.encode(filename, "UTF-8").replaceAll("\\+",
"%20");
} else {
filename = new String(filename.getBytes("UTF-8"), "ISO-8859-1");
}
} catch (UnsupportedEncodingException ex) {
System.out.println("UnsupportedEncodingException");
}
System.out.println(fileNamePath);
File file1 = new File(fileNamePath.toString());
if (!file1.exists()) {
return ;
}
// Specifying a File
response.setContentType("application/octer-stream");
response.setHeader("Content-Transfer-Encoding", "binary;");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
try {
OutputStream os = response.getOutputStream();
FileInputStream fis = new FileInputStream(fileNamePath.toString());
int ncount = 0;
byte[] bytes = new byte[512];
while ((ncount = fis.read(bytes)) != -1 ) {
os.write(bytes, 0, ncount);
}
fis.close();
os.close();
} catch (FileNotFoundException ex) {
System.out.println("FileNotFoundException");
} catch (IOException ex) {
System.out.println("IOException");
}
}
}
Your code is a bit convoluted imho. A couple of issues I see with your code
Using Path.toString to convert to a File, use the proper factory methods instead or use java.nio.Files to check the existence.
Your content-type is wrong application/octer-stream isn't a known content-type (you probably want application/octet-stream.
Copying from a Path or File is better done with either the StreamUtils from Spring or the java.nio.Files class (if you already have a Path use that).
#PostMapping("/fileDownload")
public void fileDownload(#RequestBody BoardFileDTO dto, HttpServletRequest request, HttpServletResponse response) throws UnsupportedEncodingException {
//File contains all stored paths, names, and extensions
Path fileNamePath = Paths.get(Directory, dto.getFile_save_name()).toAbsolutePath();
if (!Files.exists(fileNamePath)) {
return;
}
String filename = determineFilename(dto, request);
// Specifying a File
response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
response.setHeader("Content-Transfer-Encoding", "binary;");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
try {
Files.copy(fileNamePath, response.getOutputStream());
} catch (IOException ex) {
System.out.println("IOException");
}
}
private static String determineFilename(BoardFileDTO dto, HttpServletRequest request) {
String filename = dto.getFile_save_name(); //The name of the saved file
if (filename == null || "".equals(filename)) {
filename = dto.getFile_name();
}
String browser = request.getHeader("User-Agent");
//File Encoding
if (browser.contains("MSIE") || browser.contains("Trident") || browser.contains("Chrome")) {
filename = URLEncoder.encode(filename, StandardCharsets.UTF_8).replaceAll("\\+", "%20");
} else {
filename = new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);
}
return filename;
}
It would write it something like that. As you have a path use the java.nio.Files to check for existence and copying. Use constants for mediatypes and charsets.
Your error handling is quite basic (I would say non-existing and at least not proper) as the processing just stops and returns an empty 200 to the client. No information what so ever.
I took the liberty to factor out the logic to determine the filename, which should make your code more readable.
I have a REST API in Spring Boot Application that takes in a param of type Multipart file.
There is possibility that user may import either CSV file or Excel(.xlsx / .xsl) file of huge size which needs to be handled.
I am using Apache POI to read Excel type file and it is working fine. To my existing code, how do I efficiently handle CSV file reading also
Below is Excel file Reading Code:
#RequestMapping(value="/read", method = RequestMethod.POST)
#Transactional
public Map<String, String> read(#RequestParam("file") MultipartFile file) {
Map<String, String> response = new ArrayList();
if (!file.isEmpty()) {
ByteArrayInputStream stream;
Workbook wb;
StringBuilder contentSb = new StringBuilder();
try {
stream = new ByteArrayInputStream(file.getBytes());
wb = WorkbookFactory.create(stream);
org.apache.poi.ss.usermodel.Sheet sheet = wb.getSheetAt(wb.getActiveSheetIndex());
Iterator<Row> rowIterator = sheet.rowIterator();
System.out.println("Processing Excel file");
for (int rowIndex = 0; rowIndex <= sheet.getLastRowNum(); rowIndex++) {
Row row = sheet.getRow(rowIndex);
if (row != null) {
Cell cell = row.getCell(0);
if (cell != null) {
contentSb.append(cell.getStringCellValue()+",");
}
}
}
System.out.println("Processed Excel file");
return response;
} catch (Exception e) {
e.printStackTrace();
}
}
else {
return response;
}
}
Thank you in advance!
Goal: Get the data from a .dat file and print it to the console in Eclipse
Resources: fpfret.java and PointF.java and dichromatic.dat
I have resolved all my issues and have just a few console errors, here's my code and my question is: How do I add the getCodeBase() method?
package frp3;
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.EOFException;
import java.net.URL;
import java.util.Vector;
public class FileRead {
public static void main(String[] args) { //getDocumentBase
System.out.println(readDataFile(getCodeBase() + "dichromatic.dat", 300, 750));
}
private static String getCodeBase() {
// TODO Auto-generated method stub
return null;
}
#SuppressWarnings("unchecked")
private static PointF[] readDataFile(String filename, int min, int max) {
#SuppressWarnings("rawtypes")
Vector v = new Vector();
try {
DataInputStream dis = new DataInputStream(new BufferedInputStream((new URL(filename)).openStream()));
float f0, f1;
while (true) {
try {
f0 = dis.readFloat();
f1 = dis.readFloat();
if (min < 0 || max < 0 || (f0 >= min && f0 <= max)) {
v.addElement(new PointF(f0, f1));
}
}
catch (EOFException eof) {
break;
}
}
}
catch (Exception e) {
e.printStackTrace();
}
PointF[] array = new PointF[v.size()];
for (int i = 0; i < v.size(); i++) {
array[i] = (PointF) v.elementAt(i);
}
return array;
}
}
Here's my console errors:
java.net.MalformedURLException: no protocol: nulldichromatic.dat
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at frp3.FileRead.readDataFile(FileRead.java:27)
at frp3.FileRead.main(FileRead.java:12)
[Lfrp3.PointF;#29be513c
Here's my Project View in Eclipse:
Alright. This is actually more complex then I thought at first pass. Basically, readDataFile expects the dichromatic.dat file to be a resource available on the Internet. Look at the following line from readDataFile:
DataInputStream dis = new DataInputStream(new BufferedInputStream((new URL(filename)).openStream()));
Basically, whatever filename gets passed in, is used as a URL. For your use-case, where your file is hosted on your local filesystem, I recommend a few changes.
First, replace the above DataInputStream declaration line with:
DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream(filename)));
Second, replace getCodeBase with:
private static String getCodeBase() {
return "";
}
I've simply replace null with an empty string. Since "dichromatic.dat" is in the root of your project, it should be sufficient to use an empty string, indicating project root, as the result for getCodeBase(), as the result of that function gets pre-pended to "dichromatic.dat" before being passed to readDataFile as filename.
If you put dichromatic.dat in a different place, just modify that empty string to be the "path" that leads to the file.
Hope this helps.
Forgot to mention -- be sure to update your imports list to include import java.io.FileInputStream -- although Eclipse should handle this gracefully for you.
I searched around for this but I could not find a soultion.
Sorry about my bad description. Im not very good at this.
I have a UI class
Its calling a "lotto" class.
That lotto classes constructor is called a method named readData()
readData is reading from a file using BufferedReader
Im not getting an error message but its just not reading.
It gets stuck at BufferedReader fr = new BufferedReader... and goes to the catch thing.
If its a file not found problem how would i make it track where my file is. Im using eclipse and the program is stored on my usb. I need to hand it in to my teacher so i cant just put a location in. Is there code that tracks where my program is then takes the file from that folder?
Here is the code being used.
import java.io.*;
//contructor
public Lotto()
{
try
{
readData();
nc = new NumberChecker();
}
catch(IOException e)
{
System.out.println("There was a problem");
}
}
private void readData() throws IOException
{
//this method reads winning tickets date and pot from a file
BufferedReader file = new BufferedReader (new FileReader("data.txt"));
for(int i=0;i<5;i++)
{
System.out.println("in "+i);
winningNums[i] = file.readLine();
winningDates[i] = file.readLine();
weeksMoney[i] = Integer.parseInt(file.readLine());
System.out.println("out "+i);
}
file.close();
}
if you get an error in this line of code
BufferedReader file = new BufferedReader (new FileReader("data.txt"));
Then it is probably a FileNotFoundException
Make sure that the data.txt file is in the same folder as your compiled .class file and not the .java source.
It would be best to use a proper root to your file ex. c:\my\path\data.txt
And don't forget the \
Try surrounding the BufferedReader in a try catch and look for a file not found exception as well as IO exception. Also try putting in the fully qualified path name with double backslashes.
BufferedReader file;
try {
file = new BufferedReader (new FileReader("C:\\filepath\\data.txt"));
for(int i=0;i<5;i++)
{
System.out.println("in "+i);
winningNums[i] = file.readLine();
winningDates[i] = file.readLine();
weeksMoney[i] = Integer.parseInt(file.readLine());
System.out.println("out "+i);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
I want to upload a file to my project folder. My code is as follows:
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
File savedFile;
String destination;
List<FileItem> items = null;
try {
items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
} catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
for (FileItem item : items) {
if (item.isFormField()) {
// Process regular form field (input type="text|radio|checkbox|etc", select, etc).
} else {
// Process form file field (input type="file").
String fieldName = item.getFieldName();
String fileName = FilenameUtils.getName(item.getName());
InputStream fileContent = item.getInputStream();
String userName = (String) session.getAttribute("newUser");
destination = getServletConfig().getServletContext().getContextPath() + "\\" + userName + ".jpeg";
savedFile = new File(destination);
//Check if file exists
if(!savedFile.exists())
savedFile.createNewFile();
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(savedFile));
byte[] buffer = new byte[1024];
int len;
//Read from file and write to new file destination
while((len = fileContent.read(buffer)) >= 0) {
bos.write(buffer, 0, len);
}
//Closing the streams
fileContent.close();
bos.close();
}
}
}
When I run the jsp file and browse and select the required image and submit the form, the servlet runs but it throws IOException. The exception is throws by the line where I create a new path using savedFile.createNewFile(). Before I used that code, it threw another FileNotFoundException. I am not sure if the path that I have provided is correct.
Try to use getRealPath() method.
String fileName="/" + userName + ".jpeg";
destination = getServletContext().getRealPath(fileName);
savedFile = new File(destination);