Snippet to create a file from the contents of a blob in Java

blob, java, jdbc

Solution

You'd want to get the blob as an inputstream and dump its contents to the outputstream. So 'misery' should be something like:

Blob blob = rs.getBlob(column);
InputStream in = blob.getBinaryStream();
OutputStream out = new FileOutputStream(someFile);
byte[] buff = new byte[4096];  // how much of the blob to read/write at a time
int len = 0;

while ((len = in.read(buff)) != -1) {
    out.write(buff, 0, len);
}

If you find yourself doing a lot of IO work like this, you might look into using Apache Commons IO to take care of the details. Then everything after setting up the streams would just be:

IOUtils.copy(in, out);

Problem

I have some files stored in a database blob column in Oracle 9. I would like to have those files stored in the file system. This should be pretty easy, but I don't find the right snipped. How can I do this in java? ``` PreparedStatement ptmst = ... ResutlSet rs = pstmt.executeQuery(); rs.getBlob(); // mistery FileOutputStream out = new FileOutputStream(); out.write(); // etc et c ``` I know it should be something like that... what I don't know is what is commented as mistery Thanks EDIT I finally got this derived from David's question. This is my lazy implementation: ``` PreparedStatement pstmt = connection.prepareStatement("select BINARY from MYTABLE"); ResultSet rs = pstmt.executeQuery(); while( rs.next() ) { Blob blob = rs.getBlob("BINARY"); System.out.println("Read "+ blob.length() + " bytes "); byte [] array = blob.getBytes( 1, ( int ) blob.length() ); File file = File.createTempFile("something-", ".binary", new File(".")); FileOutputStream out = new FileOutputStream( file ); out.write( array ); out.close(); } ```

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