CODEWITHSUNDEEP
javaswingfile
Harsha
Harsha

Reputation: 3578

Convert byte array into a file without writing the file to a disk

I have saved icon size images in a mysql database in bytes, now, what I need to do is retrieve those file bytes from the database and show those images in a swing application, I have a method which gets the bytes from the database and convert it back to a file but I have to write that file in to the disk

this is my method,

public void downloadFile(int FamerId) throws Exception {
  String sql = "SELECT * FROM images WHERE famer_id=?";
  Connection con = JDBCConnectionPool.getInstance().checkOut();
  PreparedStatement ps = con.prepareStatement(sql);        
  ps.setInt(1, FamerId);
  ResultSet resultSet = ps.executeQuery();

  int count = 0;

  while (resultSet.next()) {
    ByteArrayInputStream bais;
    ObjectInputStream inputStream;

    bais = new ByteArrayInputStream(resultSet.getBytes("image"));
    inputStream = new ObjectInputStream(bais);
    SaveFile sf = (SaveFile) inputStream.readObject();
    FileOutputStream out = new FileOutputStream("fileLocation/" + resultSet.getString("image_name"));
    byte[] bytes = sf.getArray();

    int c = 0;
    while (c < bytes.length) {
      out.write(bytes[c]);
      c++;
    }

    out.close();
    inputStream.close();
    bais.close();            
    JDBCConnectionPool.getInstance().checkOut();
  }
}

but this method doesn't give what I need, please assist me.

Upvotes: 1

Views: 5443

Answers (2)

mprabhat
mprabhat

Reputation: 20323

The answer to your question is its platform dependent. From the docs

A file output stream is an output stream for writing data to a File or to a FileDescriptor. Whether or not a file is available or may be created depends upon the underlying platform. Some platforms, in particular, allow a file to be opened for writing by only one FileOutputStream (or other file-writing object) at a time. In such situations the constructors in this class will fail if the file involved is already open.

FileOutputStream is meant for writing streams of raw bytes such as image data. For writing streams of characters, consider using FileWriter.

So if you want to write to a file then file may or may not be created.

If you don't want to create the file and you are just interested in byte[] (content of the file) you can then use solution provided by @Perception or can just pass the inputStream that you have already created.

Upvotes: 0

Perception
Perception

Reputation: 80598

You can read images directly from byte streams with the ImageIO class. Assuming of course that you have previously written the image data in a compatible format. Which is hard to say given the fact that in your code you use an intermediary object input stream when reading your byte data. Here's an example of how you can create an image directly from the database without using intermediary files:

bais = new ByteArrayInputStream(resultSet.getBytes("image"));
final BufferedImage image = ImageIO.read(bais);
// pass the image to your Swing layer to be rendered.

And an example of how you would have written the data to the database, in order to be able to use this code:

final ByteArrayOutputStream baos = new ByteArrayOutputStream(64000);
ImageIO.write(image, "PNG", baos);
final byte[] data = baos.toByteArray();
// write data to database

Upvotes: 3

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