How to Convert a BufferedInputStream Blob from a Database into a Visible Image?

Convert BufferedInputStream into Image

The challenge arises when attempting to transform a Blob retrieved from a database into a visible image. In this specific case, the Blob is stored as a BufferedInputStream, and converting it directly into an image via ImageIO.read returns null.

Addressing the Issue

1. Validate the InputStream: Verify that the Blob#getBytes method returns the correct length. Ensure the file contents are not truncated.
2. Extract Binary Data Correctly: Utilize Blob#getBinaryStream instead of Blob#getBytes to retrieve the binary data, accounting for the specific characteristics of the database (e.g., H2).
3. Bypass BufferedInputStream: Bypass the BufferedInputStream by creating a ByteArrayOutputStream and writing the binary data to it. Then create a ByteArrayInputStream from the ByteArrayOutputStream for use with ImageIO.read.

Suggested Code Modifications:

public BufferedImage getPhoto(Connection con) throws IOException, SQLException {
    Blob blob = getPhoto(con);
    BufferedImage image = null;
    byte[] data;
    
    try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
         InputStream is = blob.getBinaryStream()) {
        
        int nRead;
        byte[] buffer = new byte[4096];
        while ((nRead = is.read(buffer, 0, buffer.length)) != -1) {
            baos.write(buffer, 0, nRead);
        }
        
        data = baos.toByteArray();
        image = ImageIO.read(new ByteArrayInputStream(data));
    } catch (SQLException | IOException e2) {
        e2.printStackTrace();
    }
    
    return image;
}

By implementing these modifications, the Blob is retrieved correctly, converted into a ByteArrayInputStream, and read as an image using ImageIO.read.

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