Most Robust way of reading a file or stream using Java (to prevent DoS attacks)

Question

Currently I have the below code for reading an InputStream. I am storing the whole file into a StringBuilder variable and processing this string af

Answer 1

I faced a similar issue when copying a huge binary file (which generally does not contain newline character). doing a readline() leads to reading the entire binary file into one single string causing OutOfMemory on Heap space.

Here is a simple JDK alternative:

public static void main(String[] args) throws Exception
{
    byte[] array = new byte[1024];
    FileInputStream fis = new FileInputStream(new File(""));
    FileOutputStream fos = new FileOutputStream(new File(""));
    int length = 0;
    while((length = fis.read(array)) != -1)
    {
        fos.write(array, 0, length);
    }
    fis.close();
    fos.close();
}

Things to note:

• The above example copies the file using a buffer of 1K bytes. However, if you are doing this copy over network, you may want to tweak the buffer size.

• If you would like to use FileChannel or libraries like Commons IO, just make sure that the implementation boils down to something like above