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Package org.zkoss.poi.hpsf

See: Description

Package org.zkoss.poi.hpsf Description

Processes streams in the Horrible Property Set Format (HPSF) in POI filesystems. Microsoft Office documents, i.e. POI filesystems, usually contain meta data like author, title, last saving time etc. These items are called properties and stored in property set streams along with the document itself. These streams are commonly named \005SummaryInformation and \005DocumentSummaryInformation. However, a POI filesystem may contain further property sets of other names or types.

In order to extract the properties from a POI filesystem, a property set stream's contents must be parsed into a org.apache.poi.hpsf.PropertySet instance. Its subclasses org.apache.poi.hpsf.SummaryInformation and org.apache.poi.hpsf.DocumentSummaryInformation deal with the well-known property set streams \005SummaryInformation and \005DocumentSummaryInformation. (However, the streams' names are irrelevant. What counts is the property set's first section's format ID - see below.)

The factory method org.apache.poi.hpsf.PropertySetFactory#create creates a org.apache.poi.hpsf.PropertySet instance. This method always returns the most specific property set: If it identifies the stream data as a Summary Information or as a Document Summary Information it returns an instance of the corresponding class, else the general org.apache.poi.hpsf.PropertySet.

A org.apache.poi.hpsf.PropertySet contains a list of org.apache.poi.hpsf.Sections which can be retrieved with org.apache.poi.hpsf.PropertySet#getSections. Each org.apache.poi.hpsf.Section contains a org.apache.poi.hpsf.Property array which can be retrieved with org.apache.poi.hpsf.Section#getProperties. Since the vast majority of org.apache.poi.hpsf.PropertySets contains only a single org.apache.poi.hpsf.Section, the convenience method org.apache.poi.hpsf.PropertySet#getProperties returns the properties of a org.apache.poi.hpsf.PropertySet's org.apache.poi.hpsf.Section (throwing a org.apache.poi.hpsf.NoSingleSectionException if the org.apache.poi.hpsf.PropertySet contains more (or less) than exactly one org.apache.poi.hpsf.Section).

Each org.apache.poi.hpsf.Property has an ID, a type, and a value which can be retrieved with org.apache.poi.hpsf.Property#getID, org.apache.poi.hpsf.Property#getType, and org.apache.poi.hpsf.Property#getValue, respectively. The value's class depends on the property's type. The current implementation does not yet support all property types and restricts the values' classes to String, Integer and Date. A value of a yet unknown type is returned as a byte array containing the value's origin bytes from the property set stream.

To retrieve the value of a specific org.apache.poi.hpsf.Property, use org.apache.poi.hpsf.Section#getProperty or org.apache.poi.hpsf.Section#getPropertyIntValue.

The org.apache.poi.hpsf.SummaryInformation and org.apache.poi.hpsf.DocumentSummaryInformation classes provide convenience methods for retrieving well-known properties. For example, an application that wants to retrieve a document's title string just calls org.apache.poi.hpsf.SummaryInformation#getTitle instead of going through the hassle of first finding out what the title's property ID is and then using this ID to get the property's value.

Writing properties can be done with the classes org.apache.poi.hpsf.MutablePropertySet, org.apache.poi.hpsf.MutableSection, and org.apache.poi.hpsf.MutableProperty.

Public documentation from Microsoft can be found in the appropriate section of the MSDN Library.

History

2003-09-11:

org.apache.poi.hpsf.PropertySetFactory#create(InputStream) no longer throws an org.apache.poi.hpsf.UnexpectedPropertySetTypeException.

To Do

The following is still left to be implemented. Sponsering could foster these issues considerably.

  • Convenience methods for setting summary information and document summary information properties

  • Better codepage support

  • Support for more property (variant) types

Author:
Rainer Klute (klute@rainer-klute.de)

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