## Package org.apache.poi.hpsf

See:
Description

Class Summary
ClassID: Represents a class ID (16 bytes).
Constants: Defines constants of general use.
CustomProperties: Maintains the instances of `CustomProperty` that belong to a `DocumentSummaryInformation`.
CustomProperty: This class represents custom properties in the document summary information stream.
DocumentSummaryInformation: Convenience class representing a DocumentSummary Information stream in a Microsoft Office document.
MutableProperty: Adds writing capability to the `Property` class.
MutablePropertySet: Adds writing support to the `PropertySet` class.
MutableSection: Adds writing capability to the `Section` class.
Property: A property in a `Section` of a `PropertySet`.
PropertySet: Represents a property set in the Horrible Property Set Format (HPSF).
PropertySetFactory: Factory class to create instances of `SummaryInformation`, `DocumentSummaryInformation` and `PropertySet`.
Section: Represents a section in a `PropertySet`.
SpecialPropertySet: Abstract superclass for the convenience classes `SummaryInformation` and `DocumentSummaryInformation`.
SummaryInformation: Convenience class representing a Summary Information stream in a Microsoft Office document.
Thumbnail: Class to manipulate data in the Clipboard Variant (`VT_CF`) format.
TypeWriter: Class for writing little-endian data and more.
Util: Provides various static utility methods.
Variant: The Variant types as defined by Microsoft's COM.
VariantSupport: Supports reading and writing of variant data.

Exception Summary
HPSFException: This exception is the superclass of all other checked exceptions thrown in this package.
HPSFRuntimeException: This exception is the superclass of all other unchecked exceptions thrown in this package.
IllegalPropertySetDataException: This exception is thrown when there is an illegal value set in a `PropertySet`.
IllegalVariantTypeException: This exception is thrown if HPSF encounters a variant type that is illegal in the current context.
MarkUnsupportedException: This exception is thrown if an `InputStream` does not support the `InputStream.mark(int)` operation.
MissingSectionException: This exception is thrown if one of the `PropertySet`'s convenience methods does not find a required `Section`.
NoFormatIDException: This exception is thrown if a `MutablePropertySet` is to be written but does not have a formatID set (see `MutableSection.setFormatID(ClassID)` or `MutableSection.setFormatID(byte[])`.
NoPropertySetStreamException: This exception is thrown if a format error in a property set stream is detected or when the input data do not constitute a property set stream.
NoSingleSectionException: This exception is thrown if one of the `PropertySet`'s convenience methods that require a single `Section` is called and the `PropertySet` does not contain exactly one `Section`.
ReadingNotSupportedException: This exception is thrown when HPSF tries to read a (yet) unsupported variant type.
UnexpectedPropertySetTypeException: This exception is thrown if a certain type of property set is expected (e.g.
UnsupportedVariantTypeException: This exception is thrown if HPSF encounters a variant type that isn't supported yet.
VariantTypeException: This exception is thrown if HPSF encounters a problem with a variant type.
WritingNotSupportedException: This exception is thrown when trying to write a (yet) unsupported variant type.

## Package org.apache.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 `PropertySet` instance. Its subclasses `SummaryInformation` and `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 `PropertySetFactory.create(java.io.InputStream)` creates a `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 `PropertySet`.

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

Each `Property` has an ID, a type, and a value which can be retrieved with `Property.getID()`, `Property.getType()`, and `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 `Property`, use `Section.getProperty(long)` or `Section.getPropertyIntValue(long)`.

The `SummaryInformation` and `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 `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 `MutablePropertySet`, `MutableSection`, and `MutableProperty`.

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

## History

2003-09-11:

  `PropertySetFactory.create(InputStream)` no longer throws an `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)

Copyright 2012 The Apache Software Foundation or its licensors, as applicable.