如何将Blob object转换成Java中的PDF文件？

Question

I have the following situation into a Java application.

From the database a retrieve this Blob object that is the representation of a PDF file on the DB:

Blob blobPdf = cedolinoPdf.getAllegatoBlob();

Now I have to convert it into a PDF file. How can I do this task?

Tnx

Answer 1

If the Blob is the binary representation of a PDF, all you need to do is get the bytes. If you wanted to write the PDF to a file, you could do...

Blob blobPdf = ...;
File outputFile = new File("/tmp/blah/whatever.pdf");
FileOutputStream fout = new FileOutputStream(outputFile);
IOUtils.copy(blobPdf.getBinaryStream(), fout);

This should write your PDF to a file called "/tmp/blah/whatever.pdf"

Answer 2

You can use the getBinaryStream() from the ResultSet, then you can create a file from InputStream returned by the getBinaryStream().

Your code may look something like this

 Connection connection = null; Statement statement = null; ResultSet rs = null; try { Class.forName("net.sourceforge.jtds.jdbc.Driver").newInstance(); connection = DriverManager.getConnection(connectionURL, "sa", "sa"); statement = connection.createStatement(); rs = statement.executeQuery("SELECT fileName,blobFile FROM tblBlobFiles"); if (rs.next()) { String filename = rs.getString(1); Blob blob = rs.getBlob(2); InputStream is = blob.getBinaryStream(); FileOutputStream fos = new FileOutputStream("C:\\\\DownloadedFiles"+ "\\\\" + filename); int b = 0; while ((b = is.read()) != -1) { fos.write(b); } } } catch (IOException e) { e.getMessage (); e.printStackTrace(); System.out.println(e); } catch (SQLException e) { e.getMessage (); e.printStackTrace(); System.out.println(e); } 

If you need all the blobs, do a iteration on the resultset

Answer 3

you can use Java NIO

InputStream fileBolb = rs.getBinaryStream("columnName");
ReadableByteChannel rbc = Channels.newChannel(fileBolb );
FileOutputStream fos = new FileOutputStream(filePath + fname);
fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
fos.close();
rbc.close();

Answer 4

Converting Blob into PDF is not that much straight forward task. I had used itext.5.5.9.jar to achieve same, here is my code:

public static void blobToPDF(String[] args) throws IOException {

    Blob blobPdf = ....;

    com.itextpdf.kernel.pdf.PdfReader newreader = null;

    try (InputStream targetStream = blobPdf.getBinaryStream()) {

        newreader = new com.itextpdf.kernel.pdf.PdfReader(targetStream);

        System.out.println("Reading PDF using com.itextpdf.kernel.pdf.PdfReader...");
        System.out.println("PDF read success with kernel package ");
        System.out.println("PDF length = " + newreader.getFileLength());

    } catch (InvalidPdfException | FileNotFoundException | SQLException ipe) {
        ipe.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {

        if (newreader != null)
            newreader.close();
    }
}