Develop Reference

Is there a way to combine a outputstream and printwriter in one request?

I have to do a file transfer, in my case a pdf, through socket in java for my homework. Usually I requested text and got text back, but this time I have to send a file through socket. In my investigation I discovered that file transfers are made with Fileinput(output)streams. My problem is that the request to the server has to look something like this:
File file = new File(pathToFile);
Pirntwriter out = new PrintWriter(Socket s.getOutputStream());
Outputstream outFile = s.getOutputStream();
int count
out.write("user file\r\n"
+ file.getName()+"\r\n"
+ file.length()+"\r\n"
+ "body\r\n");
// send file but im not sure how
byte[] buffer = new buffer with size of file.length()
while ((count = in.read(buffer)) > 0){
outFile.write(buffer, 0, count);
}
out.flush
outFile.flush
Unfortunately this doesn't work for me. In this way the server counts the requests as two different outputs. Is there a way to combine both Outputstreams or write the request in one single Outputstream?

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();

Java servlet and IO: Create a file without saving to disk and sending it to the user

I`m hoping can help me out with a file creation/response question.
I know how to create and save a file. I know how to send that file back to the user via a ServletOutputStream.
But what I need is to create a file, without saving it on the disk, and then send that file via the ServletOutputStream.
The code above explains the parts that I have. Any help appreciated. Thanks in Advance.
// This Creates a file
//
String text = "These days run away like horses over the hill";
File file = new File("MyFile.txt");
Writer writer = new BufferedWriter(new FileWriter(file));
writer.write(text);
writer.close();
// Missing link goes here
//
// This sends file to browser
//
InputStream inputStream = null;
inputStream = new FileInputStream("C:\\MyFile.txt");
byte[] buffer = new byte[8192];
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int bytesRead;
while ( (bytesRead = inputStream.read(buffer)) != -1)
baos.write(buffer, 0, bytesRead);
response.setContentType("text/html");
response.addHeader("Content-Disposition", "attachment; filename=Invoice.txt");
byte[] outBuf = baos.toByteArray();
stream = response.getOutputStream();
stream.write(outBuf);

You don't need to save off a file, just use a ByteArray stream, try something like this:
inputStream = new ByteArrayInputStream(text.getBytes());
Or, even simpler, just do:
stream.write(text.getBytes());
As cHao suggests, use text.getBytes("UTF-8") or something similar to specify a charset other than the system default. The list of available charsets is available in the API docs for Charset.

URL Connection (FTP) in Java - Simple Question

I have a simple question. I'm trying to upload a file to my ftp server in Java.
I have a file on my computer, and I want to make a copy of that file and upload it. I tried manually writing each byte of the file to the output stream, but that doesn't work for complicated files, like zip files or pdf files.
File file = some file on my computer;
String name = file.getName();
URL url = new URL("ftp://user:password#domain.com/" + name +";type=i");
URLConnection urlc = url.openConnection();
OutputStream os = urlc.getOutputStream();
//then what do I do?
Just for kicks, here is what I tried to do:
OutputStream os = urlc.getOutputStream();
BufferedReader br = new BufferedReader(new FileReader(file));
String line = br.readLine();
while(line != null && (!line.equals(""))) {
os.write(line.getBytes());
os.write("\n".getBytes());
line = br.readLine();
}
os.close();
For example, when I do this with a pdf and then try and open the pdf that I run with this program, it says an error occurred when trying to open the pdf. I'm guessing because I am writing a "\n" to the file? How do I copy the file without doing this?

Do not use any of the Reader or Writer classes when you're trying to copy the byte-for-byte exact contents of a binary file. Use these only for plain text! Instead, use the InputStream and OutputStream classes; they do not interpret the data at all, while the Reader and Writer classes interpret the data as characters. For example
OutputStream os = urlc.getOutputStream();
FileInputStreamReader fis = new FileInputStream(file);
byte[] buffer = new byte[1000];
int count = 0;
while((count = fis.read(buffer)) > 0) {
os.write(buffer, 0, count);
}
Whether your URLConnection usage is correct here, I don't know; using Apache Commons FTP (as suggested elsewhere) would be an excellent idea. Regardless, this would be the way to read the file.

Use a BufferedInputStream to read and BufferedOutputStream to write. Take a look at this post: http://www.ajaxapp.com/2009/02/21/a-simple-java-ftp-connection-file-download-and-upload/
InputStream is = new FileInputStream(localfilename);
BufferedInputStream bis = new BufferedInputStream(is);
OutputStream os =m_client.getOutputStream();
BufferedOutputStream bos = new BufferedOutputStream(os);
byte[] buffer = new byte[1024];
int readCount;
while( (readCount = bis.read(buffer)) > 0) {
bos.write(buffer, 0, readCount);
}
bos.close();

FTP usually opens another connection for data transfer.
So I am not convinced that this approach with URLConnection is going
to work.
I highly recommend that you use specialized ftp client. Apache commons
may have one.
Check this out
http://commons.apache.org/net/api/org/apache/commons/net/ftp/FTPClient.html

How to create ZIP file for a list of "virtual files" and output to httpservletresponse

My goal is to put multiple java.io.File objects into a zip file and print to HttpServletResponse for the user to download.
The files were created by the JAXB marshaller. It's a java.io.File object, but it's not actually on the file system (it's only in memory), so I can't create a FileInputStream.
All resources I've seen use the OutputStream to print zip file contents. But, all those resources use FileInputStream (which I can't use).
Anyone know how I can accomplish this?

Have a look at the Apache Commons Compress library, it provides the functionality you need.
Of course "erickson" is right with his comment to your question. You will need the file content and not the java.io.File object. In my example I assume that you have a method
byte[] getTheContentFormSomewhere(int fileNummer) which returns the file content (in memory) for the fileNummer-th file. -- Of course this function is poor design, but it is only for illustration.
It should work a bit like this:
void compress(final OutputStream out) {
ZipOutputStream zipOutputStream = new ZipOutputStream(out);
zipOutputStream.setLevel(ZipOutputStream.STORED);
for(int i = 0; i < 10; i++) {
//of course you need the file content of the i-th file
byte[] oneFileContent = getTheContentFormSomewhere(i);
addOneFileToZipArchive(zipOutputStream, "file"+i+"."txt", oneFileContent);
}
zipOutputStream.close();
}
void addOneFileToZipArchive(final ZipOutputStream zipStream,
String fileName,
byte[] content) {
ZipArchiveEntry zipEntry = new ZipArchiveEntry(fileName);
zipStream.putNextEntry(zipEntry);
zipStream.write(pdfBytes);
zipStream.closeEntry();
}
Snipets of your http controller:
HttpServletResponse response
...
response.setContentType("application/zip");
response.addHeader("Content-Disposition", "attachment; filename=\"compress.zip\"");
response.addHeader("Content-Transfer-Encoding", "binary");
ByteArrayOutputStream outputBuffer = new ByteArrayOutputStream();
compress(outputBuffer);
response.getOutputStream().write(outputBuffer.toByteArray());
response.getOutputStream().flush();
outputBuffer.close();

Turns out I'm an idiot :) The file that was being "created" was saving to invalid path and swallowing the exception, so I thought it was being "created" ok. When I tried to to instantiate a new FileInputStream, however, it complained that file didn't exist (rightly so). I had a brainfart and assumed that the java.io.File object actually contained file information in it somewhere. But as erickson pointed out, that was false.
Thanks Ralph for the code, I used it after I solved the invalid pathing issue.
My code:
ZipOutputStream out = new ZipOutputStream(response.getOutputStream());
byte[] buf = new byte[1024];
File file;
InputStream in;
// Loop through entities
for (TitleProductAccountApproval tpAccountApproval : tpAccountApprovals) {
// Generate the file
file = xmlManager.getXML(
tpAccountApproval.getTitleProduct().getTitleProductId(),
tpAccountApproval.getAccount().getAccountId(),
username);
// Write to zip file
in = new FileInputStream(file);
out.putNextEntry(new ZipEntry(file.getName()));
int len;
while ((len = in.read(buf)) > 0) {
out.write(buf, 0, len);
}
out.closeEntry();
in.close();
}
out.close();