用Java顺序编写大型PDF

Question

I am looking for a Java library that let's you write large PDFs sequentially with a minimum amount of memory. Most of the libraries I had a look at has to build up the document in memory first before you can actually write it.

The problem I have to deal with are OutOfMemoryErrors. It would be great if I could flush the writer programmatically whenever needed eg for each page.

Does anyone have any recommendations? I need something with a license along the lines of the LGPL (so not the GPL or the Affero GPL that iText uses).

Answer 1

You can do that with iText . It supports writing to OutputStream s .

Answer 2

The free version of Docmosis has a fairly open license so it might suit you. It uses a template-approach which is different from building from code. Docmosis processes all documents in a stream-based fashion since it's intended for singificant parallel use and for large documents. It also allows you to offload the most CPU intensive part processing to another server. Hope that helps.

Answer 3

I actually, had same issue as you do, a friend help me out, but he did in C# and using an api called GhostScriptSharp, you should check for it.

I can't give you a copy of the code, since its copyrighted, but i'm sure it would help you out, since the tool i think is builded on Java.

Answer 4

jPod can swap indirect objects and supports incremental writing.

This is still not optimal as you need an "increment" on each flush, but better than nothing...

EDIT

Öhhh - this is one of the famous examples of self describing code :-) Your're right, theres not much of a tutorial or that - but the Javadoc is quite good.

• jPod writes incremental by default. See "CosDocument.setWriteModeHint" to set to full mode.
• The example "CreateDoc" and "AppendPage" are simple examples of how to add pages. You may do the same and call "save" every 10 or 100 pages. This should "soften" all references to pages in memory and if not held by some other references of yours, the can be garbage collected.

THere's still the question how you fill the pages? THere are examples dealing with content streams, too (DrawText,..). BUT jPod is not like iText, jasper or whatever. There's only PDF model abstractions. You have no "Layouter" or "Renderer" that creates page content from text, html or something like that. How do you do this?