Sending big file using FileInputStream/ObjectOutputStream

问题

I need help on my homework, any help will be much appreciated. I can send small files without a problem. But when i try to send let’s say a 1GB file byte array sends OutOfMemoryError so i need a better solution to send file from server to client. How can i improve this code and send big files, please help me.

Server Code:

    FileInputStream fis = new FileInputStream(file);
    byte[] fileByte = new byte[fis.available()]; //This causes the problem.
    bytesRead = fis.read(fileByte);
    oos = new ObjectOutputStream(sock.getOutputStream());
    oos.writeObject(fileByte);

Client Code:

    ois = new ObjectInputStream(sock.getInputStream());
    byte[] file = (byte[]) ois.readObject();
    fos = new FileOutputStream(file);
    fos.write(file);

回答1:

Just split the array to smaller chunks so that you don't need to allocate any big array.

For example you could split the array into 16Kb chunks, eg new byte[16384] and send them one by one. On the receiving side you would have to wait until a chunk can be fully read and then store them somewhere and start with next chunk.

But if you are not able to allocate a whole array of the size you need on server side you won't be able to store all the data that you are going to receive anyway.

You could also compress the data before sending it to save bandwidth (and time), take a look at ZipOutputStream and ZipInputStream.

回答2:

Don't read the whole file into memory, use a small buffer and write while you are reading the file:

BufferedOutputStream bos = new BufferedOutputStream(sock.getOutputStream())

File file = new File("asd");
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
byte[] buffer = new byte[1024*1024*10];
int n = -1;
while((n = bis.read(buffer))!=-1) {
  bos.write(buffer,0,n):
}

Use Buffered* to optimize the writing and reading from Streams

回答3:

Here's how I solved it:

Client Code:

 bis=new BufferedInputStream(sock.getInputStream());
 fos = new FileOutputStream(file);
 int n;
 byte[] buffer = new byte[8192];
 while ((n = bis.read(buffer)) > 0){
 fos.write(buffer, 0, n);}

Server Code:

 bos= new BufferedOutputStream(sock.getOutputStream());
 FileInputStream fis = new FileInputStream(file);
 BufferedInputStream bis = new BufferedInputStream(fis);
 int n=-1;
 byte[] buffer = new byte[8192];
 while((n = bis.read(buffer))>-1) 
 bos.write(buffer,0,n);

回答4:

Depending on whether or not you have to write the code yourself, there are existing libraries which solve this problem, e.g. rmiio. If you are not using RMI, just plain java serialization, you can use the DirectRemoteInputStream, which is kind of like a Serializable InputStream. (this library also has support for things like auto-magically compressing the data).

Actually, if you are only sending file data, you would be better off ditching the Object streams and use DataInput/DataOutput streams. first write an integer indicating the file length, then copy the bytes directly to the stream. on the receiving side, read the integer file length, then read exactly that many bytes.

when you copy the data between streams, use a small, fixed size byte[] to move chunks of data between the input and output streams in a loop. there are numerous examples of how to do this correctly available online (e.g. @ErikFWinter's answer).

来源：https://stackoverflow.com/questions/10819516/sending-big-file-using-fileinputstream-objectoutputstream

标签

java

bytearray

inputstream

outputstream