Develop Reference

Why can't I read an object from a binary file using ObjectInputStream wrapped with a FIleInputStream?

public class JavaApplication {
public static void main(String[] args) throws IOException{
URL u = new URL("https://www.javatpoint.com/java-string-valueof");
byte[]bytes= u.openStream().readAllBytes();
ObjectOutputStream output= new ObjectOutputStream(
new FileOutputStream("binary.dat"));
output.write(bytes);
output.close();
//Scanning the URL works just not the try and catch block
try{
ObjectInputStream input = new ObjectInputStream(new FileInputStream
("binary.dat"));
byte[]byte1= (byte[])input.readObject();
String any;
for(int i=0; i<byte1.length; i++){
any=String.valueOf(byte1[i]);
System.out.println(any);
}
input.close();
}
catch(Exception e){
System.out.println(e);}
}
}
I used a new byte array to read the object from file, use String.valueOf() to obtain the String value of the byte, then a for-loop to iterate the String. What am I doing wrong?

As the first commenter said, your main problem was not using writeObject. The only other problem is the way you turn the bytes into text. Your code will result in the 'ascii' code of the character being printed instead of the character itself. In fact you can simplify the output code as follows:
import java.io.*;
import java.net.*;
public class JavaApplication {
public static void main(String[] args) throws IOException {
URL u = new URL("https://www.javatpoint.com/java-string-valueof");
byte[] bytes = u.openStream().readAllBytes();
ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream("binary.dat"));
output.writeObject(bytes);
output.close();
try {
ObjectInputStream input = new ObjectInputStream(new FileInputStream("binary.dat"));
byte[] byte1 = (byte[]) input.readObject();
System.out.println(new String(byte1));
input.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}

To solve your problem, I prefer you :
Add implementation of URLConnection for avoidance from Http Status 403 / Forbidden. Reference
use ByteArrayOutputStream to write the byte and save it into file using ObjectOutputStream
if you read with readObject() you must write with writeObject()
public class JavaApplication {
public static void main(String[] args) throws IOException, ClassNotFoundException {
URL u = new URL("https://www.javatpoint.com/java-string-valueof");
URLConnection uc = u.openConnection();
uc.addRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
InputStream is = null;
try {
is = uc.getInputStream();
byte[] byteChunk = new byte[4096]; // Or whatever size you want to read in at a time.
int n;
while ((n = is.read(byteChunk)) > 0) {
baos.write(byteChunk, 0, n);
}
} catch (IOException e) {
System.err.printf("Failed while reading bytes from %s: %s", u.toExternalForm(), e.getMessage());
} finally {
if (is != null) {
is.close();
}
}
byte[] bytes = baos.toByteArray();
ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream("binary.dat"));
output.writeObject(bytes);
output.close();
//Scanning the URL works just not the try and catch block
try {
ObjectInputStream input = new ObjectInputStream(new FileInputStream("binary.dat"));
byte[] byte1 = (byte[]) input.readObject();
String any;
for (int i = 0; i < byte1.length; i++) {
any = String.valueOf(byte1[i]);
System.out.println(any);
}
input.close();
} catch (IOException e) {
System.out.println(e);
}
}
}

Get progress of readBytes in android

I've already seen
Is it possible to check progress of URLconnection.getInputStream()?
https://stackoverflow.com/a/20120451/5437621
I'm using the following code to download a file from internet:
try {
InputStream is = new URL(pdfUrl).openStream();
byte[] pdfData = readBytes(is);
return pdfData;
} catch (IOException e) {
e.printStackTrace();
return null;
}
public byte[] readBytes(InputStream inputStream) throws IOException {
ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
int len = 0;
while ((len = inputStream.read(buffer)) != -1) {
byteBuffer.write(buffer, 0, len);
}
return byteBuffer.toByteArray();
}
Is there any method I can get the progress of the file being downloaded ?
The answers I have seen are using a while loop but I don't understand how to use it in this case.
EDIT:
I'm using this in AsyncTask:
protected byte[] doInBackground(String... url) {
pdfUrl = url[0];
try {
InputStream is = new URL(pdfUrl).openStream();
DownloadBytes downloadData = readBytes(is);
byte[] pdfData = downloadData.getBytes();
progress = downloadData.getProgress();
return pdfData;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
How can I adjust publishProgress() in this method ?

EOFExcpetion while deserialization by byte array

I've got a EOFException while decompress and deserialization a byte array.
Stacktrace:
java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2324)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2793)
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:799)
at java.io.ObjectInputStream.(ObjectInputStream.java:299)
at com.chuck.pack.ResourcePacket.load(ResourcePacket.java:44)
// Functions related to load
public static ResourcePacket load(String packetName) {
try {
byte[] bytes = uncompress(fileToByteArray(new File(packetName)));
ByteArrayInputStream in = new ByteArrayInputStream(bytes);
ObjectInputStream objIn = new ObjectInputStream(in); // Error occured here
return (ResourcePacket) objIn.readObject();
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
private static byte[] uncompress(byte[] bytes) {
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
Inflater ifl = new Inflater();
ifl.setInput(bytes);
byte[] buffer = new byte[4*1024];
while(ifl.finished()) {
int size = ifl.inflate(buffer);
out.write(buffer, 0, size);
}
out.close();
return out.toByteArray();
} catch (Exception ex) {
ex.printStackTrace();
System.out.println("Error while load");
}
return null;
}
private static byte[] fileToByteArray(File file) {
byte[] bytes = new byte[(int) file.length()];
try {
FileInputStream fileInputStream = new FileInputStream(file);
fileInputStream.read(bytes);
fileInputStream.close();
} catch (IOException ex) {
ex.printStackTrace();
}
return bytes;
}
// Functions related to save
public void save() {
try {
byte[] bytes = compress(toByteArray());
//byte[] bytes = toByteArray();
FileOutputStream fileOutputStream = new FileOutputStream(packetName);
fileOutputStream.write(bytes);
fileOutputStream.close();
System.out.println("Packet saved (" + resourceFiles.length + " Files)");
} catch (IOException ex) {
ex.printStackTrace();
System.exit(-1);
}
}
private byte[] compress(byte[] bytes) {
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
Deflater dfl = new Deflater();
dfl.setLevel(Deflater.BEST_SPEED);
dfl.setInput(bytes);
dfl.finish();
byte[] tmp = new byte[4*1024];
while(!dfl.finished()) {
int size = dfl.deflate(tmp);
out.write(tmp, 0, size);
}
out.close();
return out.toByteArray();
} catch (IOException ex) {
ex.printStackTrace();
System.out.println("Error while save");
}
System.exit(-1);
return null;
}
private byte[] toByteArray() {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = null;
try {
out = new ObjectOutputStream(bos);
out.writeObject(this);
byte[] bytes = bos.toByteArray();
return bytes;
} catch(IOException ex) {
ex.printStackTrace();
System.out.println("Error while create byte array");
}
System.exit(-1);
return null;
}
Someone an idee to fix this?

In the uncompress(..) method the while loop:
while(ifl.finished()) {
int size = ifl.inflate(buffer);
out.write(buffer, 0, size);
}
should be
while(!ifl.finished()) {
int size = ifl.inflate(buffer);
out.write(buffer, 0, size);
}
Otherwise the result of uncompress(..) is an empty byte array if the method terminates.

Google Cloud Storage createOrReplace file is broken (different size, ...)

I tried to upload a stream (restlet memoryfile) to gcs. But the file has another filesize and is a little different so that the file is marked as "broken".
I tried is local and on google app engine. While debugging to this part the stream looks good in size InputStream inputStream = item.getInputStream();
But the result in the store isn't that size. There are 4 Bits at the beginning: ’[NUL][ENQ]
Where are they from?
List<FileItem> items;
try {
MemoryFileItemFactory factory = new MemoryFileItemFactory();
RestletFileUpload restletFileUpload = new RestletFileUpload(factory);
items = restletFileUpload.parseRequest(req);
//items = restletFileUpload.parseRepresentation(entity);
for (FileItem item : items) {
if (!item.isFormField()) {
MediaType type = MediaType.valueOf(item.getContentType());
GcsFileOptions options = new GcsFileOptions.Builder().mimeType(type.getName()).acl("public-read").build();
GcsOutputChannel outputChannel = gcsService.createOrReplace(fileName, options);
ObjectOutputStream oout = new ObjectOutputStream(Channels.newOutputStream(outputChannel));
InputStream inputStream = item.getInputStream();
copy(inputStream, oout);
//oout.close();
}
}
} catch (FileUploadException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
private void copy(InputStream input, OutputStream output) throws IOException {
try {
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = input.read(buffer);
while (bytesRead != -1) {
output.write(buffer, 0, bytesRead);
bytesRead = input.read(buffer);
}
} finally {
input.close();
output.close();
}
}
private final GcsService gcsService = GcsServiceFactory.createGcsService(new RetryParams.Builder()
.initialRetryDelayMillis(10)
.retryMaxAttempts(10)
.totalRetryPeriodMillis(15000)
.build());

Remove the finally close statements from the copy-function and close the GcsOutputChannel instead. Further you don't need to do this: ObjectOutputStream oout = new ObjectOutputStream(Channels.newOutputStream(outputChannel));
Maybe that adds the extra-bits
Something like that:
GcsOutputChannel outputChannel = gcsService.createOrReplace(fileName, options);
InputStream inputStream = item.getInputStream();
try {
copy(inputStream, Channels.newOutputStream(outputChannel));
} finally {
outputChannel.close();
inputStream.close();
}
private void copy(InputStream input, OutputStream output) throws IOException {
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = input.read(buffer);
while (bytesRead != -1) {
output.write(buffer, 0, bytesRead);
bytesRead = input.read(buffer);
}
}

GZIP compression to a byte array

I am trying to write a class that can compress data. The below code fails (no exception is thrown, but the target .gz file is empty.)
Besides: I don't want to generate the .gz file directly like it is done in all examples. I only want to get the compressed
data, so that I can e.g. encrypt it before writting the data to a file.
If I write directly to a file everything works fine:
import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;
public class Zipper
{
public static void main(String[] args)
{
byte[] dataToCompress = "This is the test data."
.getBytes(StandardCharsets.ISO_8859_1);
GZIPOutputStream zipStream = null;
FileOutputStream fileStream = null;
try
{
fileStream = new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
zipStream = new GZIPOutputStream(fileStream);
zipStream.write(dataToCompress);
fileStream.write(compressedData);
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
try{ zipStream.close(); }
catch(Exception e){ }
try{ fileStream.close(); }
catch(Exception e){ }
}
}
}
But, if I want to 'bypass' it to the byte array stream it does not produce a single byte - compressedData is always empty.
import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;
public class Zipper
{
public static void main(String[] args)
{
byte[] dataToCompress = "This is the test data."
.getBytes(StandardCharsets.ISO_8859_1);
byte[] compressedData = null;
GZIPOutputStream zipStream = null;
ByteArrayOutputStream byteStream = null;
FileOutputStream fileStream = null;
try
{
byteStream = new ByteArrayOutputStream(dataToCompress.length);
zipStream = new GZIPOutputStream(byteStream);
zipStream.write(dataToCompress);
compressedData = byteStream.toByteArray();
fileStream = new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
fileStream.write(compressedData);
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
try{ zipStream.close(); }
catch(Exception e){ }
try{ byteStream.close(); }
catch(Exception e){ }
try{ fileStream.close(); }
catch(Exception e){ }
}
}
}

The problem is that you are not closing the GZIPOutputStream. Until you close it the output will be incomplete.
You just need to close it before reading the byte array. You need to reorder the finally blocks to achieve this.
import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;
public class Zipper
{
public static void main(String[] args)
{
byte[] dataToCompress = "This is the test data."
.getBytes(StandardCharsets.ISO_8859_1);
try
{
ByteArrayOutputStream byteStream =
new ByteArrayOutputStream(dataToCompress.length);
try
{
GZIPOutputStream zipStream =
new GZIPOutputStream(byteStream);
try
{
zipStream.write(dataToCompress);
}
finally
{
zipStream.close();
}
}
finally
{
byteStream.close();
}
byte[] compressedData = byteStream.toByteArray();
FileOutputStream fileStream =
new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
try
{
fileStream.write(compressedData);
}
finally
{
try{ fileStream.close(); }
catch(Exception e){ /* We should probably delete the file now? */ }
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
I do not recommend inititalizing the stream variables to null, because it means your finally block can also throw a NullPointerException.
Also note that you can declare main to throw IOException (then you would not need the outermost try statement.)
There is little point in swallowing exceptions from zipStream.close();, because if it throws an exception you will not have a valid .gz file (so you should not proceed to write it.)
Also I would not swallow exceptions from byteStream.close(); but for a different reason - they should never be thrown (i.e. there is a bug in your JRE and you would want to know about that.)

I've improved JITHINRAJ's code - used try-with-resources:
private static byte[] gzipCompress(byte[] uncompressedData) {
byte[] result = new byte[]{};
try (ByteArrayOutputStream bos = new ByteArrayOutputStream(uncompressedData.length);
GZIPOutputStream gzipOS = new GZIPOutputStream(bos)) {
gzipOS.write(uncompressedData);
// You need to close it before using bos
gzipOS.close();
result = bos.toByteArray();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
private static byte[] gzipUncompress(byte[] compressedData) {
byte[] result = new byte[]{};
try (ByteArrayInputStream bis = new ByteArrayInputStream(compressedData);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
GZIPInputStream gzipIS = new GZIPInputStream(bis)) {
byte[] buffer = new byte[1024];
int len;
while ((len = gzipIS.read(buffer)) != -1) {
bos.write(buffer, 0, len);
}
result = bos.toByteArray();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}

If you are still looking an answer you can use the below code to get the compressed byte[] using deflater and decompress it using inflater.
public static void main(String[] args) {
//Some string for testing
String sr = new String("fsdfesfsfdddddddsfdsfssdfdsfdsfdsfdsfdsdfggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggghghghghggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggfsdfesfsfdddddddsfdsfssdfdsfdsfdsfdsfdsdfggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggghghghghggggggggggggggggggggggggggggggggggggggggg");
byte[] data = sr.getBytes();
System.out.println("src size "+data.length);
try {
compress(data);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static byte[] compress(byte[] data) throws IOException {
Deflater deflater = new Deflater();
deflater.setInput(data);
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);
deflater.finish();
byte[] buffer = new byte[1024];
while (!deflater.finished()) {
int count = deflater.deflate(buffer);
outputStream.write(buffer, 0, count);
}
outputStream.close();
byte[] output = outputStream.toByteArray();
System.out.println("Original: " + data.length );
System.out.println("Compressed: " + output.length );
return output;
}

To compress
private static byte[] compress(byte[] uncompressedData) {
ByteArrayOutputStream bos = null;
GZIPOutputStream gzipOS = null;
try {
bos = new ByteArrayOutputStream(uncompressedData.length);
gzipOS = new GZIPOutputStream(bos);
gzipOS.write(uncompressedData);
gzipOS.close();
return bos.toByteArray();
} catch (IOException e) {
e.printStackTrace();
}
finally {
try {
assert gzipOS != null;
gzipOS.close();
bos.close();
}
catch (Exception ignored) {
}
}
return new byte[]{};
}
To uncompress
private byte[] uncompress(byte[] compressedData) {
ByteArrayInputStream bis = null;
ByteArrayOutputStream bos = null;
GZIPInputStream gzipIS = null;
try {
bis = new ByteArrayInputStream(compressedData);
bos = new ByteArrayOutputStream();
gzipIS = new GZIPInputStream(bis);
byte[] buffer = new byte[1024];
int len;
while((len = gzipIS.read(buffer)) != -1){
bos.write(buffer, 0, len);
}
return bos.toByteArray();
} catch (IOException e) {
e.printStackTrace();
}
finally {
try {
assert gzipIS != null;
gzipIS.close();
bos.close();
bis.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
return new byte[]{};
}

You can use the below function, it is tested and working fine.
In general, your code has serious problem of ignoring the exceptions! returning null or simply not printing anything in the catch block will make it very difficult to debug
You do not have to write the zip output to a file if you want to process it further (e.g. encrypt it), you can easily modify the code to write the output to in-memory stream
public static String zip(File inFile, File zipFile) throws IOException {
FileInputStream fis = new FileInputStream(inFile);
FileOutputStream fos = new FileOutputStream(zipFile);
ZipOutputStream zout = new ZipOutputStream(fos);
try {
zout.putNextEntry(new ZipEntry(inFile.getName()));
byte[] buffer = new byte[BUFFER_SIZE];
int len;
while ((len = fis.read(buffer)) > 0) {
zout.write(buffer, 0, len);
}
zout.closeEntry();
} catch (Exception ex) {
ex.printStackTrace();
return null;
} finally {
try{zout.close();}catch(Exception ex){ex.printStackTrace();}
try{fis.close();}catch(Exception ex){ex.printStackTrace();}
}
return zipFile.getAbsolutePath();
}

Most of the examples have wrong exception handling.
public static byte[] gzipBytes(byte[] payload) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try (GZIPOutputStream gzip = new GZIPOutputStream(baos)) {
gzip.write(payload);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
// note: toByteArray should be called after try-with-resources, not inside
return baos.toByteArray();
}
public static byte[] gunzipBytes(byte[] gzPayload) {
ByteArrayInputStream bais = new ByteArrayInputStream(gzPayload);
try (GZIPInputStream gzip = new GZIPInputStream(bais)) {
// java 9+ required for this method
return gzip.readAllBytes();
} catch (IOException e) {
throw new UncheckedIOException("Error while unpacking gzip content", e);
}
}

Try with this code..
try {
String inputFileName = "test.txt"; //may use your file_Path
String zipFileName = "compressed.zip";
//Create input and output streams
FileInputStream inStream = new FileInputStream(inputFileName);
ZipOutputStream outStream = new ZipOutputStream(new FileOutputStream(zipFileName));
// Add a zip entry to the output stream
outStream.putNextEntry(new ZipEntry(inputFileName));
byte[] buffer = new byte[1024];
int bytesRead;
//Each chunk of data read from the input stream
//is written to the output stream
while ((bytesRead = inStream.read(buffer)) > 0) {
outStream.write(buffer, 0, bytesRead);
}
//Close zip entry and file streams
outStream.closeEntry();
outStream.close();
inStream.close();
} catch (IOException ex) {
ex.printStackTrace();
}
Also may be helpful this one..
http://www.java-samples.com/java/zip_files_in_a_folder_using_java.htm