How to avoid overwriting files while writing multiple files from BLOB data in DB in JAVA

Question

I am retrieving data from DB BLOB(csv) data into CSV files . While writing the data into files each and every time the files are getting over write . Below the code I used for writing the files . If I close the writer inside the for loop then , only one file gets writes others are not getting loaded. If I closed outside the loop then same file gets overwrites every time .

//code:

while (rs.next()) {
                String filename = rs.getString("file_name");
                String path = ( calPath + filename );
                File file = new File(path);
                FileOutputStream output = new FileOutputStream(file ,true);
                Blob blob = rs.getBlob("file_data");
                byte[] bytes1 = blob.getBytes(1l, (int) blob.length());
                for (int i = 0; i < bytes1.length; i++) {
                     output.write(bytes1);
                                                                   //output.close();
                }

                output.close();

            }

            //connection.close();

Answer 1

Due to your inner for Loop it writing file again and again. so remove your inner for loop it will work.

 while (rs.next()) {
            String filename = rs.getString("file_name");
            String path = ( calPath + filename );
            File file = new File(path);
            FileOutputStream output = new FileOutputStream(file ,true);
            Blob blob = rs.getBlob("file_data");
            byte[] bytes1 = blob.getBytes(1l, (int) blob.length());
           // for (int i = 0; i < bytes1.length; i++) {
                 output.write(bytes1);
                                                               //output.close();
           // }

            output.close();

        }

Answer 2

i think you should check file first. you can write if file not exist

    File file = new File(path);

    if(!file.exists() && !file.isDirectory()) { 
        // do your writing?
    }

EDIT: also you can compare sizes if you want more specific comparison