I am new with networking in java and i want to achieve a file transfer system that server downloads a file from client (client computer file to server) i searched the internet for a bunch of tutorials but all of them seems to give me a error or dont do anything but i found 10 year old tutorial that worked here is the link:
Click me and i did small change to it that made it more stable but there is a problem that i cannot solve when the file downloads on the server the file is still in use by the server and i noticed that the loop does not quit and doesnt close the file stream when its done now here is the code:
Client:
File fl = new File(splitedstreamcommand[2]);
FileInputStream fin = new FileInputStream(fl);
int i = -1;
while((i = fin.read()) != -1){
output.write(i);
output.flush();
//System.out.print((char) i);
}
fin.close();
The output is a ObjectOutputStream
Server:
File fl = new File("C:\\testfolder\\thetestfiledownloaded.txt");
//FileOutputStream fos = new FileOutputStream("C:\\testfolder\\thetestfiledownloaded.txt");
int i = -1;
if(fl.createNewFile()){
FileOutputStream fout = new FileOutputStream(fl);
while((i=input.read()) != -1){
//System.out.print((char) i);
fout.write(i);
System.out.println("Downloading....");
}
//System.out.println("Still downloading....");
fout.close();
//fin.close();
System.out.println("File downloaded.");
}
The input is a ObjectInputStream and now the loop that is the problem is here in the server the while loop that is reading bytes it stops when its done reading but it doesnt quit the loop and continue executing the code like the File Downloaded string that should print out and the file is still in use. I think this code is broken because its old but this is the only code that is working to me for some reason soo how can i fix this issue? Thanks. Sorry about the bad question format and explanation if you cannot understand tell me and i can try to format it.
Related
this is my directory structure
Inside the server I have the following code for saving a file that gets sent from the client
fileName = reader.readLine();
DataInputStream dis = null;
try {
dis = new DataInputStream(csocket.getInputStream());
FileOutputStream fos = new FileOutputStream(fileName);
buffer = new byte[4096];
int fileSize = 15123;
int read = 0;
int totalRead = 0;
int remaining = fileSize;
while((read = dis.read(buffer, 0, Math.min(buffer.length, remaining))) > 0) {
totalRead += read;
remaining -= read;
fos.write(buffer, 0, read);
}
fos.close();
dis.close();
} catch (IOException e) {
}
break;
I'm wondering how I would go about saving the file within the xml folder? I've tried using getClass().getResource and such but nothing seems to work.
fileName is just a simple string containing the name of the file, not a path or anything.
I get the correct path using this code:
File targetDir = new File(getClass().getResource("xml").getPath());
File targetFile = new File(targetDir, fileName);
targetFile.createNewFile();
System.out.println(targetFile.getAbsolutePath());
dis = new DataInputStream(csocket.getInputStream());
FileOutputStream fos = new FileOutputStream(targetFile.getAbsolutePath(), false);
But it still won't save it there...
The best way is to receive explicitly the target path for storing files, either through a .properties file or a command-line argument. In this way, you make your program flexible to be installed and adapted in different environments.
But if you wish your program to assume the target directory automatically, the best option is to set a relative path before creating the FileOutputStream, as long as you start your program always from the same path:
File targetDir=new File("xml");
File targetFile=new File(targetDir, fileName);
FileOutputStream fos = new FileOutputStream(targetFile);
This will work assuming the program is started from server as current directory.
Update
Other minor suggestions about your program:
Never base the exit condition of the loop on a hard-coded file size, because it is not possible to know it a priori. Instead, check explicitly if the value returned by read is less than 0 => that means End Of File reached.
Consequently, do not bother to calculate the exact amount of data to get through a call to read. Just enter the buffer size, because you are setting a maximum data size.
Never let exceptions catched without a proper treatment: If you know how to make your program recover, enter a proper code into the catch block. Otherwise, you'd better not catch them: Declare them in the throws clause and let them be propagated to the caller.
Always create stream resources through the try-with-resources instruction, to ensure they got closed at the end:
try (FileOutputStream fos = new FileOutputStream(...))
{
// ... use fos...
}
Save unnecessary instructions: If you don't care about if the file already exists on the filesystem or not, don't call createNewFile. But if you care, check the returned value and bifurcate consequently.
I try to create file and it does created but not at ProjectName\src\com\company\xml but in ProjectName\out\production\ProjectName\com\company\xml
my code:
File targetDir = new File(this.getClass().getResource("xml").getPath());
// get the parent of the file
String parentPath = targetDir.getParent( );
String fileName="xml/name.txt";
//do something
File targetFile = new File(parentPath, fileName);
targetFile.createNewFile();
Just pay attention that after compilation you will try to save it into a jar file and it a complicated thing to do.
usually you need to save file into file outside from your jar(separate in the root) like this:
I run a Minecraft server for my friends, and a while back I very shoddily put together an installer which would download mods and install them properly to the correct location.
After about 6 hours of figuring out how to do what I was trying to do, I successfully got a working installer. I tried it again today, and found that it has stopped working. I've been trying to fix it, but to no avail. I cannot find any solution which actually gets the whole file to download, rather, an empty 4KB file is created. I tried on a different computer and the same thing happened. I'm running the latest version of Java.
This is the method I'm using to download the file. I have tried solutions using a ReadableByteChannel, but that yielded similar results, with a 1KB empty file.
public void download(String filename, URL url) {
try {
String fileName = filename;
URL link = url;
InputStream in = new BufferedInputStream(link.openStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
StringBuffer stringBuffer = new StringBuffer();
while (-1 != (n = in.read(buf))) {
out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();
FileOutputStream fos = new FileOutputStream(fileName);
fos.write(response);
fos.close();
System.out.println("Download complete!");
} catch (Exception e) {
System.out.println("Download failed, something went wrong!");
}
}
Is there something wrong with the method above? I can't really wrap my head around how downloading the file works, else I'd troubleshoot it myself. Any methods I can find on Google are going about it in pretty much the same way.
Printing stack trace:
at Install.download(Install.java:93)
at Install.downloadFile(Install.java:41)
at Install.main(Install.java:106)
at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
EDIT: Problem solved, used a different file hosting site to host the file. Now I just need to figure out how I can update the file without changing the URL.
I am trying to Compare last modified date of two excel files and replace the old file with new file.
In Scenario : When there is no file in the first place, so the code copies the file to that location and later reads it.
Issue is : It throws a FileNotFound exception when the excel file is not present on the server,even after writing the file to the
server(via code),but the file is not seen on the server. It works on
my machine(windows),but fails when deployed on server.
Again, it works like charm when the file is present on the server,while the old is being replaced by the new file.
Can you please help and explain on why its failing in the above scenario,and only on server ?
if(row.getValue("fileType").toString().equals("xlsx")&&checkindatefolder.after(localdate))
{
messagelist.add("we are going to get the replace file in the server");
InputStream inp=folder.getFile();
ZipInputStream izs = new ZipInputStream(inp);
ZipEntry e = null;
while ((e = izs.getNextEntry()) != null) {
System.out.println("e.isDirectory(): "+e.isDirectory());
if (!e.isDirectory()) {
filename=e.getName();
System.out.println("filename: "+filename);
FileOutputStream os=new FileOutputStream("path"+e.getName());
byte[] buffer = new byte[4096];
int read=0;
System.out.println("writing to file");
while ((read=izs.read(buffer))> 0) {
System.out.println("1111");
os.write(buffer,0,read);
}
System.out.println("writing to file complete");
inp.close();
os.flush();
os.close();
}
}
Do all parts of the path exist?
So in your example:
/u01/app/webapps/out/pj/Create.xlsx
Do all subdirectories exist?
/u01/app/webapps/out/pj
If not, than trying to write there might fail with a FileNotFoundException.
You should create the directories with Files.creatDirectories(Path) first.
Hi I am trying to write some code in my program so I can grab a file from the internet but it seems that is not working. Can someone give me some advice please ? Here is my code. In this case I try to download an mp3 file from the last.fm website, my code runs perfectly fine but when I open my downloads directory the file is not there. Any idea ?
public class download {
public static void main(String[] args) throws IOException {
String fileName = "Death Grips - Get Got.mp3";
URL link = new URL("http://www.last.fm/music/+free-music-downloads");
InputStream in = new BufferedInputStream(link.openStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
while (-1!=(n=in.read(buf)))
{
out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();
FileOutputStream fos = new FileOutputStream(fileName);
fos.write(response);
fos.close();
System.out.println("Finished");
}
}
Every executing program has a current working directory. Often times, it is the directory where the executable lives (if it was launched in a "normal" way).
Since you didn't specify a path (in fileName), the file will be saved with that name in the current working directory.
If you want the file to be saved in your downloads directory, specify the full path. E.g.
String fileName = "C:\\Users\\YOUR_USERNAME\\Downloads\\Death Grips - Get Got.mp3";
Note how I've escaped the backslashes. Also note that there are methods for joining paths in Java. There is a way to get the current working directory in Java.
I've looked around for some script or some tutorial for downloading file using Java, and then moving them to a different directory. I've seen a lot of questions similar to mine answered, but they all vary. Is there a definite way to do this? I currently learning Java and don't have enough experience make functioning script for this. Could anyone help?
I personally think this is the best way to download a file from the web.
When you download the file, it is stored in current running program, not on the hard drive, unless you specify it to.
URL url;
URLConnection con;
DataInputStream dis;
FileOutputStream fos;
byte[] fileData;
try {
url = new URL("http://website.com/file.pdf"); //File Location goes here
con = url.openConnection(); // open the url connection.
dis = new DataInputStream(con.getInputStream());
fileData = new byte[con.getContentLength()];
for (int q = 0; q < fileData.length; q++) {
fileData[q] = dis.readByte();
}
dis.close(); // close the data input stream
fos = new FileOutputStream(new File("/Users/kfang/Documents/Download/file.pdf")); //FILE Save Location goes here
fos.write(fileData); // write out the file we want to save.
fos.close(); // close the output stream writer
}
catch(Exception m) {
System.out.println(m);
}