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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN" "document-v20.dtd">
<document>
<header>
<title>Apache POI™ - POIFS - Documents embedded in other documents</title>
<subtitle>Overview</subtitle>
<authors>
<person name="Nick Burch" email="nick@apache.org"/>
<person name="Yegor Kozlov" email="yegor@apache.org"/>
</authors>
</header>
<body>
<section><title>Overview</title>
<p>It is possible for one OLE 2 based document to have other
OLE 2 documents embedded in it. For example, an Excel file
may have a Word document and a PowerPoint slideshow
embedded as part of it.</p>
<p>Normally, these other documents are stored in subdirectories
of the OLE 2 (POIFS) filesystem. The exact location of the
embedded documents will vary depending on the type of the
master document, and the exact directory names will differ
each time. To figure out exactly which directory to look
in, you will either need to process the appropriate OLE 2
linking entry in the master document, or simple iterate
over all the directories in the filesystem.</p>
<p>As a general rule, you will find the same OLE 2 entries
in the subdirectories, as you would've found at the root
of the filesystem were a document to not be embedded.</p>
<section><title>Files embedded in Excel</title>
<p>Excel normally stores embedded files in subdirectories
of the filesystem root. Typically these subdirectories
are named starting with MBD, with 8 hex characters following.</p>
</section>
<section><title>Files embedded in Word</title>
<p>Word normally stores embedded files in subdirectories
of the ObjectPool directory, itself a subdirectory of the
filesystem root. Typically these subdirectories and named
starting with an underscore, followed by 10 numbers.</p>
</section>
<section><title>Files embedded in PowerPoint</title>
<p>PowerPoint does not normally store embedded files
in the OLE2 layer. Instead, they are held within records
of the main PowerPoint file.
<br/>See the <a href="./../slideshow/how-to-shapes.html#OLE">HSLF Tutorial</a>
for how to retrieve embedded OLE objects from a presentation</p>
</section>
</section>
<section><title>Listing POIFS contents</title>
<p>POIFS provides a simple tool for listing the contents of
OLE2 files. This can allow you to see what your POIFS file
contents, and hence if it has any embedded documents in it,
and where.</p>
<p>The tool to use is <em>org.apache.poi.poifs.dev.POIFSLister</em>.
This tool may be run from the command line, and takes a filename
as its parameter. It will print out all the directories and
files contained within the POIFS file.</p>
</section>
<section><title>Opening embedded files</title>
<p>All of the POIDocument classes (HSSFWorkbook, HSLFSlideShow,
HWPFDocument and HDGFDiagram) can either be opened from
a POIFSFileSystem, or from a specific directory within a
POIFSFileSystem. So, to open embedded files, simply locate the
appropriate DirectoryNode that represents the subdirectory
of interest, and pass this + the overall POIFSFileSystem to
the constructor.</p>
<p>I you want to extract the textual contents of the embedded file,
then open the appropriate POIDocument, and then pass this to
the extractor class, instead of simply passing the POIFSFilesystem
to the extractor.</p>
</section>
</body>
</document>
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