[Javascript] Newline Character or Break Line in Textarea Field

Hi Friends,

We put a textarea to a form. Submit the form. Edit the form. Everything works fine. Textarea seems to display everything alright. But what if we want to load the form using javascript for editing?

In this case, if the text in textarea has a newline character, Javascript will throw error. Since it will be coming like this.. if text area text is  "This is my msg.\nRavi" then to javascript it will appear like

var msg = "This is my msg.

Ravi";

Which is an error.. Javascript will not do anything further. I could not find any solid solution for this but here is what can be done. I was getting the data from java so..

<%

// In java the data is stored with Html escape for all special characters etc.

msg = msg.replaceAll("\n", "<br />"); 

%>

// In javascript get the msg and replace all <br> with \n
var tmsg = "<%=msg%>";
tmsg = replaceAll(tmsg, "<br />", "\n");
tmsg = unescape(tmsg); // needed to get all special characters

Now put this content anywhere you want. 

$(#textAreaMsg).html(tmsg);

And the replaceAll function is  
function replaceAll(txt, replace, with_this) {   return txt.replace(new RegExp(replace, 'g'),with_this); }

Thats it.:)

[MySQL] Users and Permissions : Grant all on..

To create a user in mysql use -

CREATE USER 'ravi'@'localhost' IDENTIFIED BY 'password';

To grant all permissions use -

GRANT ALL PRIVILEGES ON *.* TO 'ravi'@'localhost' WITH GRANT OPTION;

GRANT ALL ON *.* TO 'ravi'@'localhost' WITH GRANT OPTION; //also works

To grant selected permissions use -

GRANT SELECT,DELETE,UPDATE ON *.* TO 'ravi'@'localhost' WITH GRANT OPTION;

Reference : MySQL Reference

Enjoy :) 

PDF Viewer : View PDF on Websites

Hi Friends,

Did you ever think of any apporach about viewing pdf files on website.. Its not difficult one. Just convert the pdf to image and display. I wondered how google worked and set up Google books, well you will have the answer. Click on this link. If the link is not working no issue. Whats in that is written in next lines.

The link which you just clicked is http://books.google.com/books?id=fcW1xl1BejUC&pg=PA308&img=1&zoom=3&hl=en&sig=ACfU3U0viP5hPVQFiFCyoDc4_zeXPmco-Q&w=685 which is nothing but a dynamic generated url to get the image from google servers. So, even Google is using the images. Answer of standard question "Why" is simple.. Browsers. They cant render parse and render pdf(AFAIK) but they can display images.

The same approach we followed when it came to think about a pdf viewer. There are some very powerful libraries are availabe which can convert any pdf to certain images formats without any error. Unfortunately most of them are not free.. To help open source in this area Apache provided PDFbox and Swinglabs provided PDF renderer. Both are very small and lightweight libraries which enable us to create/edit/convert pdfs.

Below code shows how we can convert pdf to images. But for basics, A pdf is actually a document with pages. And when I say convert to image its not like taking a screenshot but the content of pdf are drawn in a 2d image(At least pdfbox does).To know more about the API docs just download the libraries along with the documentation.

Convert using PDFBox-
    public GetSpecificPage(int pageNum, String pathFile, String pathPage) {
        try {
            PDDocument document = PDDocument.load(pathFile);
            List list = document.getDocumentCatalog().getAllPages();
            int count = document.getNumberOfPages();
            PDPage page = list.get(pageNum);
            int dpi = 75; // Dots per inch
            BufferedImage image = page.convertToImage(BufferedImage.TYPE_INT_RGB, dpi);
            File imageFile = new File("D:/tests/pdfbox/" + pageNum + "-dpi-" + dpi + ".png");
            ImageIO.write(image, "png", imageFile);
        } catch (Exception ex) {
            Logger.getLogger(GetSpecificPage.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
Well even using PDFBox this is not the only approach to extract something out.
            File f = new File("D:/tests/pdfbox/1.pdf");
            FileInputStream fis = null;
            fis = new FileInputStream(f);
            PDFParser parser = new PDFParser(fis);
            parser.parse();
            COSDocument cosDoc = parser.getDocument();
            PDDocument pdDoc = new PDDocument(cosDoc);
            Splitter splitter = new Splitter();
            List pages = splitter.split(pdDoc);
            for (int i = 0; i < pages.size(); i++) {
                PDDocument pageDoc = pages.get(i);
                String fileNameNew = "page_" + i + ".pdf";
                pageDoc.save("D:/tests/pdfs/" + fileNameNew);
                pageDoc.close();
            }
            fis.close();
            cosDoc.close();
            pdDoc.close();
And now with the PDF Renderer- Its bit different.
            File file = new File("D:/tests/pdfbox/1.pdf");
            RandomAccessFile raf = new RandomAccessFile(file, "r");
            FileChannel channel = raf.getChannel();
            ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
            PDFFile pdfFile = new PDFFile(buf);
            int num = pdfFile.getNumPages();
            for (int i = 0; i < 100; i++) {
                PDFPage page = pdfFile.getPage(i);

                //get the width and height for the doc at the default zoom
                int width = (int) page.getBBox().getWidth();
                int height = (int) page.getBBox().getHeight();

                Rectangle rect = new Rectangle(0, 0, width+(width%60), height+(height%60));
                int rotation = page.getRotation();
                Rectangle rect1 = rect;
                if (rotation == 90 || rotation == 270) {
                    rect1 = new Rectangle(0, 0, rect.height, rect.width);
                }

                //generate the image
                BufferedImage img = (BufferedImage) page.getImage(
                        rect.width, rect.height, //width & height
                        rect1, // clip rect
                        null, // null for the ImageObserver
                        true, // fill background with white
                        true // block until drawing is done
                        );

                ImageIO.write(img, "png", new File("D:/tests/pdf1/" + i + ".png"));
            }
Thats it in this. We explored just one small but powerful feature of both Libraries. To learn more just download and use.. Its simple.

Next step is to view the images on browser.. That's an easy task if you dont want to take care of security and performance. I believe a lot of free javascript libraries are available which can display. But if we need security and performance we need to take care of images which we are rendering on browser and caching + some other applicable mechanisms which can help with the performance. Anyways It completely depends on the user's choice on how to view them on Web. :D

Cheers!!!
Ravi Kumar Gupta