Develop Reference

Java OutStreamWriter to ByteArrayInputStream

I am writing a csv file in a very old java application so i can not use all the new Java 8 streams.
Writer writer = new OutputStreamWriter(new FileOutputStream("file.csv"));
writer.append("data,");
writer.append("data,");
...
Then I need to transform the writer object into a ByteArrayInputStream.
How can i do it ?
Thanks in advance.
Best regards.

This depends on what you are trying to do.
If you are writing a bunch of data to the file and THEN reading the file you will want to use a FileInputStream in place of your ByteArrayInputStream.
If you want to write a bunch of data to a byte array then you should take a look at using a ByteArrayOutputStream. If you then need to read the byte array as a ByteArrayInputStream you can pass the ByteArrayOutputStream into the input stream like what is shown below. Keep in mind this only works for writing and THEN reading. You can not use this like a buffer.
//Create output stream
ByteArrayOutputStream out = new ByteArrayOutputStream();
//Create Writer
Writer writer = new OutputStreamWriter(out);
//Write stuff
...
//Close writer
writer.close();
//Create input stream using the byte array from out as input.
ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());

Short answer: you can't.
A ByteArrayInputStream is just not assignable from a OutputStreamWriter.
Since you're probably after write, you can just read the file back to a byte[] and then construct a ByteArrayInputStream with it:
File file = new File("S:\\Test.java");
FileInputStream fis = new FileInputStream(file);
byte[] content = new byte[(int) file.length()];
fis.read(content,0,content.length);
ByteArrayInputStream bais = new ByteArrayInputStream(content);

BouncyCastle openPGP encrypt byte[] array as csv file

I have gotten my code to be able to load in a public key, and encrypt a byte[] array with a public key someone else has provided. However, when i decrypt the file, it doesn't have a .csv extension. I can open it in Excel and it looks like a csv once I open it, but the file just doesn't have any extension associated to it, so I have to weirdly open it in Excel.
I've also attached my code below and I just couldn't figure out where to modify it so that when I decrypt it using Kleopatra, it shows with a .csv extension. I tried to change my output stream to a .csv from a .gpg file, but then it throws an error saying that it could not determine whether this is a OpenPGP signature. I think I have to do something with the lData.open() method, but the only options I can put there are PGPLiteralData.TEXT, BINARY, and UTF8. Maybe this has to do with adding a signature to the file?
Btw, for the code below, the public key is already loaded into a variable called pubkey.
byte[] bytesArray = getAccessChannels(customerAlias);
OutputStream out = new FileOutputStream("/path/to/file/eData.gpg");
Security.addProvider(new BouncyCastleProvider());
ByteArrayOutputStream bOut = new ByteArrayOutputStream();
PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedDataGenerator.ZIP);
OutputStream cos = comData.open(bOut); // open it with the final destination
PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();
OutputStream pOut = lData.open(cos, PGPLiteralData.TEXT, "Report.csv", bytesArray.length, new Date());
pOut.write(bytesArray);
lData.close();
comData.close();
PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(new BcPGPDataEncryptorBuilder(SymmetricKeyAlgorithmTags.AES_256).setSecureRandom(new SecureRandom()));
cPk.addMethod(new BcPublicKeyKeyEncryptionMethodGenerator(pubKey));
byte[] bytes = bOut.toByteArray();
OutputStream cOut = cPk.open(out, bytes.length);
cOut.write(bytes); // obtain the actual bytes from the compressed stream
cOut.close();

Nevermind, I just needed to change the file extension to eData.csv.gpg...this took me a whole 2 days

Writing a File object to a file in java

For a class, I have to send a file of any type from my client to a server. I have to handle each packet individually and use UDP. I have managed to transfer the file from the client to the server, and I now have a file object which I cannot figure out how to save to a user specified directory.
f = new File(path + '\\' + filename);//path and filename are user specified.
FileOutputStream foutput = new FileOutputStream(f);
ObjectOutputStream output = new ObjectOutputStream(foutput);
output.writeObject(result);//result is a File
output.flush();
output.close();
Any time I run this code, it writes a new file with the appropriate name, but the text file I am testing ends up just containing gibberish. Is there any way to convert the File object to a file in the appropriate directory?
EDIT: As it turns out, I was misunderstanding what, exactly, a file is. I have not been transferring the data, but rather the path. How do I transfer an actual file?

ObjectOutputStream is a class that outputs a specific format of data to a text file. Only ObjectInputStream's readObject() can decoding that text file.
If you open the text file , it is just gibberish ,as you have seen.
you want this:
FileOutputStream fos = new FileOutputStream(path + '\\' + filename);
FileInputStream fis = new FileInputStream(result);
byte[] buf = new byte[1024];
int hasRead = 0;
while((hasRead = fis.read(buf)) > 0){
fos.write(buf, 0, hasRead);
}
fis.close();
fos.close();

If I understand your question, how about using a FileWriter?
File result = new File("result.txt");
result.createNewFile();
FileWriter writer = new FileWriter(result);
writer.write("Hello user3821496\n"); //just an example how you can write a String to it
writer.flush();
writer.close();

Is there an alternative to FileOutputStream type , which does not create a file?

To process some images in my android application I currently use code like this:
FileOutputStream fileOuputStream = new FileOutputStream(imgpath);
[..DO SOME STUFF..]
Bitmap data = BitmapFactory.decodeByteArray(bFile, 0, bFile.length, options);
data.compress(Bitmap.CompressFormat.JPEG, 90, fileOuputStream);
[..DO SOME STUFF..]
File file = new File(imgpath);
FileInputStream imageInFile = new FileInputStream(file);
byte imageData[] = new byte[(int) file.length()];
imageInFile.read(imageData);
[..DO SOME STUFF..]
file.delete();
//NOTE: The code is all in the same method
the problem is that passing my image from one part of the code to another using this method creates a temporary file.
I was looking for a way to read / write the file data using a memory variable, something like "generic stream" in which store data in order to replace use of "FileInputStream " and "FileOutputStream " and do not write temporary file.

If you are able to use an InputStream or OutputStream you can use ByteArrayInputStream or ByteArrayOutputStream for in memory handling of the data.
If you have two thread you can also use PipedInputStream and PipedOutputStream together to communicate between the threads.

You could write your data to a ByteArrayOutputStream and use the byte array of that stream:
ByteArrayOutputStream out = new ByteArrayOutputStream();
data.compress(Bitmap.CompressFormat.JPEG, 90, out);
// now take the bytes out of your Stream
byte[] imgData = out.toByteArray();

Connection from server to client, file transfer

By using instance of PrintStream and println function, I can send raw string to the client(s). But, I want to send whole .html file to the client in order to see the web page. For this reason, What should be my approach ? I have tried to read a file and give the whatever is read on the println function. But, attempts is failed.

Maby something like this will help:
// sendfile
File myFile = new File ("source.html");
byte [] mybytearray = new byte [(int)myFile.length()];
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
OutputStream os = sock.getOutputStream();
System.out.println("Sending...");
os.write(mybytearray,0,mybytearray.length);
os.flush();
sock.close();