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Converting docx/ODT to image using Java

I am working on a Spring REST service based web application (UI is based on HTML5, backbone.js). The actual requirement is, an uploaded document (could be any document like excel, word, ppt, pdf etc) requires an preview option using which an user can view the document in the browser (user may or may not have office installed).
My idea is to convert the documents into images and display them to the user. On searching, i found multiple ways to convert a PDF to image but not much ODT to image (Note: I am looking for an open source). JODConverter, docx4j can be used to convert the documents to pdf. Then I can convert these PDFs to images. But is this the right way. Is there any other efficient way to achieve the same. Please suggest and point me to the right direction.
Thanks in advance.
Gopi

Yes, you won't do any better than .docx to .pdf to image. You really need a stable workflow, and this is as good as you'll find for this purpose, unless you're running on a Microsoft server and you have access to the official Microsoft Office stuff.
For previews, docx4j or similar will do just fine. Not everything converts perfectly, but it should be fine for a preview.

PDF Open Office or MS Word

I am new to java, I have to read a PDF, Open Office or MS Word file and make changes in the file and render as PDF document on my web page. Please someone tell me which of these file's API or SDK is easy to use and also tell me best SDK for this. So I can read, Update and render easily. file also contains Table but there is no image.

We use Apache POI to read Microsoft Office files. There are many libraries for PDF in Java. iText is something I have used. Once you pick the tools, do a selective search on Stack Overflow. There are plenty of discussions around these tools.

Depending on the types of updates you are doing, modifying PDF is going to be a problem - it's not intended for editing. You might have to find some way of converting the PDF to something first, then edit. Depending on the types of changes you want to make and the documents you are working from even editing DOC and Writer files is going to be tricky. They are all different formats.
As Jayan mentioned, iText and POI may help you a little. OpenOffice Writer documents can be edited by unzipping then modifying the XML or using the UNO API. Word documents can be editied by using MS Office automation (bad idea), converting to OpenOffice first then editing, or if DOCX, unzipping and processing the XML.
Good luck.

how to convert a HTML web page into a PDF file using Java

i've been searching on the internet on how to convert a HTML page into a PDF file using Java. i found a lot of pointers, and in short, they don't work or are too difficult to implement. i also downloaded a commercial product, pdf4ml; the API is something i'd be happy to work with, except that when i crawled a simple page on wikipedia, i get a out of memory error (setting Xmx to 1024 M). in some approaches, they suggest converting HTML -> XHTML -> FO -> PDF. however, i am getting a lot of exceptions for the XHTML-to-FO XLS file; and reading the documentations, it's not something that i have enough time to understand right now.
here are my questions/concerns.
1. is there another cohesive API out there that will easily convert HTML to PDF (commercial or not)?
2. is there a way i can simply capture a HTML page and store it as a single file. this approach would be similar to using internet explorer's way of saving a web page as a web archive (single file, MHT format)?
any help is appreciated. (btw, i know this question has been asked repeatedly, but in addition to the original spirit of the question, i'm opened to other ways). thanks.

Try wkhtmltopdf, which is using WebKit. Another option (I'm using that currently) is using OpenOffice (remote controlled via macros).

you may use iText open source Java lib for that, and read this
or use YaHPConverter open source Java lib.
or do this whith help of icepdf popular open source lib
or use pd4ml, but it not free, only trial.
or use this, and this is man for it.

My 2 cents using opensource tools:
You can use either Capture screenshots with Selenium or WebDriver to save html page's screenshot in an image file from your Java code. And once you have image file you can convert it to pdf again from your Java code.
EDIT:
It seems you can do all that in 1 step using itext Html to Pdf

I am not sure but you could Try
1) cobra html rendering engine http://lobobrowser.org/cobra.jsp
2) htmleditorkit -- part of jdk
3) JWebPane
Use the rendering kit to parse and render html. The rendered out put is a swing component. Swing component can be used by itext to generate pdf file out put

You can try out Pdfcrowd. It is an easy to use commercial online API with many options and with support for Java.
It can create PDF either from web pages or raw HTML code.

How to show the printable document directly in acrobat with out saving?

I am using PD4ML to print a PDF file and It is working fine. Now the thing is I want show that file directly in acrobat with out save that file. In Local version I am using
Program.launch(getFilePath());
It is working fine but in web version I am unable to get that.
Can you please suggest me, Its very helpful.
Thanks,
Vara Kumar PJD

The web isn't like your desktop, so forget about doing things on the web the way you do them on the desktop without at least some effort.
Know that you don't read PDF files on the web using Acrobat without a browser plugin. Or some other reader like Foxit Reader.
My recommendation: forget about doing it this way. Either server your pdf as a file that can be downloaded, or read this SO post about embedding PDF in HTML.

I don't think this will be possible: "showing file outside browser in an application without user consent" because that is how browser are made for security reason. The best you can do is, as pointed in earlier post is by darioo, to show file in browser or prompt user to download/open.

Multiple file uploader with previews

I'm trying to find something that will let users upload multiple files to a website. The requirements are that it let them easily select multiple files (preferably with something like check boxes) and that it displays a preview of the images they select.
I'd prefer to only use Javascript or Flash if possible, but Java is also an option (this needs to work on platforms where Silverlight isn't available).
So far all I've been able to find are things that use the native file selector (which doesn't show previews on Windows, and makes it unclear that you can select multiple by holding ctrl).
I'm not sure if the preview requirement is even possible, but it's the most important.

This is a firefox solution:
It uses the FileReader javascript object to load, display and upload images.
http://hacks.mozilla.org/2011/01/how-to-develop-a-html5-image-uploader/
It still doesnt show previews in the FileSelection dialog but at least allows you to preview the images before uploading.
And here is a ready made java applet solution:
http://jumploader.com/doc_overview.html

To upload multiple files I use RichFaces rich:fileUpload component.
Concerning the preview, I've got the similar problem and the best I found after couple of days of googling is following.
Alfresco has the same problem and resolved it with :
An open office which runs in server mode (socket) and all the office documents are sent by alfresco to open office in order to convert them in PDF
Those PDF are converted to .swf viewer thanks to SWFTOOLS
This .swf is integrated in the HTML
For images, it uses ImageMagick to create small version of the file I suppose
Personnaly, I will try to implement it this way :
Converting office documents to PDF thanks to open office in socket mode
Transform the first page of the PDF into a PNG thanks to JPedal library
Diplay that PNG to the end user
For images I would perhaps use ImageMagick too ... but for now, I'm using Seam Image.scaleToFit API

I am assuming 2 things here:
1) Some kind of client/enduser will be doing the file upload
2) You get some kind of say on what the client installs on their computer to help make this happen.
If this is the case, my first suggestion would be:
Give them FTP or SFTP client software to upload files. The php page you make can have a link to Filezilla, along with instructions on how to use it. ftp and sftp are THE protocols to use for transferring files. HTTP is just not designed(well) for it, nor are browsers.
Once the user has the (S)FTP client software installed, you can give them URL's to upload files to that are specific to their user account, and you can have a backend script process and load/move files that they upload. It's pretty easy to create a local temporary directory using a server side script, have the client upload files via ftp, then go back to the web browser and click a button that says "Done uploading, please process my stuff".
The browser can even give back confirmations on everything that gets uploaded/processed.