</li>
<li>
- The <link href="#sec4">fourth section</link> will tell you how to write
- property set streams - once it is written. Writing is still quite
- rudimentary in HPSF and you have to understand the <link
- href="#sec3">third section</link> before you should think about writing
- properties. Stick to the Javadoc API documentation to find out more about
- writing property sets!
+ The <link href="#sec4">fourth section</link> tells you how to write
+ property set streams. Writing is still rudimentary in HPSF. You have to
+ understand the <link href="#sec3">third section</link> before you should
+ think about writing properties. Check the Javadoc API documentation to
+ find out about the details!
</li>
</ol>
<li>Each section has a format ID. The format ID of the first section in a
property set determines the property set's type. For example, the first
- (and only) section of the SummaryInformation property set has a format
+ (and only) section of the summary information property set has a format
ID of <code>F29F85E0-4FF9-1068-AB-91-08-00-2B-27-B3-D9</code>. You can
get the format ID with <code>Section.getFormatID()</code>.</li>
<note>This section describes how to write properties.</note>
- <section><title>Overview</title>
+ <section><title>Overview of Writing Properties</title>
<p>Writing properties is possible at a low level only at the moment. You
have to deal with property IDs and variant types to write
- properties. There are no convenient classes or convenient methods for
+ properties. There are no convenience classes or convenience methods for
dealing with summary information and document summary information streams
- yet. If you have not already done so, you should read <link
- href="#sec3">section 3</link> to understand the following.</p>
+ yet. Therefore you should have read <link href="#sec3">section 3</link>
+ to understand what follows in this section.</p>
<p>HPSF's writing capabilities come with the classes
- <code>MutablePropertySet</code>, <code>MutableSection</code>, and
- <code>MutableProperty</code> and some helper classes. The "mutable"
- classes extend their superclasses <code>PropertySet</code>,
+ <code>MutablePropertySet</code>, <code>MutableSection</code>,
+ <code>MutableProperty</code>, and some helper classes. The "mutable"
+ classes extend their respective superclasses <code>PropertySet</code>,
<code>Section</code>, and <code>Property</code> and provide "set" and
"write" methods.</p>
<li>Create a <code>MutablePropertySet</code> instance.</li>
<li>Get hold of a <code>MutableSection</code>. You can either retrieve
- the one that is always present in a new <code>MutablePropertySet</code>
- or create a new <code>MutableSection</code> and add it to the
- <code>MutablePropertySet</code>.
+ the one that is always present in a new <code>MutablePropertySet</code>,
+ or you have to create a new <code>MutableSection</code> and add it to
+ the <code>MutablePropertySet</code>.
</li>
<li>Set any <code>Section</code> fields as you like.</li>
<li>Create as many <code>MutableProperty</code> objects as you need. Set
each property's ID, type, and value. Add the
- <code>MutableProperties</code> to the <code>MutableSection</code>.
+ <code>MutableProperty</code> objects to the
+ <code>MutableSection</code>.
</li>
<li>Create further <code>MutableSection</code>s if you need them.</li>
</section>
<section><title>Low-level Writing Functions In Details</title>
- <fixme author="Rainer Klute">This section is still to be written.</fixme>
+ <p>Writing properties is introduced by an artificial but simple example: a
+ program creating a new document (aka POI file system) which contains only
+ a single document: a summary information property set stream. The latter
+ will hold the document's title only. This is artificial in that it does
+ not contain any Word, Excel or other kind of useful application document
+ data. A document containing just a property set is without any practical
+ use. However, is makes the example very simple, and you will get quickly
+ used to writing properties.</p>
+
+ <p>Here's the source code of the sample application. You can also find it
+ in the "examples" section of the POI source code
+ distribution. Explanations are following below.</p>
+
+ <source>package org.apache.poi.hpsf.examples;
+
+import java.io.*;
+
+import org.apache.poi.hpsf.*;
+import org.apache.poi.hpsf.wellknown.*;
+import org.apache.poi.poifs.filesystem.*;
+
+public class WriteTitle
+{
+
+ public static void main(final String[] args)
+ throws WritingNotSupportedException, IOException
+ {
+ /* Check whether we have exactly one command-line argument. */
+ if (args.length != 1)
+ {
+ System.err.println("Usage: " + WriteTitle.class.getName() +
+ "destinationPOIFS");
+ System.exit(1);
+ }
+
+ final String fileName = args[0];
+ final POIFSFileSystem poiFs = new POIFSFileSystem();
+
+ /* Create a mutable property set. Initially it contains a single section
+ * with no properties. */
+ final MutablePropertySet mps = new MutablePropertySet();
+
+ /* Retrieve the section the property set already contains. */
+ final MutableSection ms = (MutableSection) mps.getSections().get(0);
+
+ /* Turn the property set into a summary information property. This is
+ * done by setting the format ID of its first section to
+ * SectionIDMap.SUMMARY_INFORMATION_ID. */
+ ms.setFormatID(SectionIDMap.SUMMARY_INFORMATION_ID);
+
+ /* Create an empty property. */
+ final MutableProperty p = new MutableProperty();
+
+ /* Fill the property with appropriate settings so that it specifies the
+ * document's title. */
+ p.setID(PropertyIDMap.PID_TITLE);
+ p.setType(Variant.VT_LPWSTR);
+ p.setValue("Sample title");
+
+ /* For writing the property set into a POI file system it has to be
+ * handed over to the POIFS.createDocument() method as an input stream
+ * which produces the bytes making out the property set stream. */
+ final InputStream is = mps.toInputStream();
+
+ /* Create the summary information property set in the POI file
+ * system. It is given the default name most (if not all) summary
+ * information property sets have. */
+ poiFs.createDocument(is, SummaryInformation.DEFAULT_STREAM_NAME);
+
+ /* Write the whole POI file system to a disk file. */
+ poiFs.writeFilesystem(new FileOutputStream(fileName));
+ }
+
+}</source>
+
+ <p>The application expects the name of the POI file system to be created
+ on the command line. It checks that there is exactly a single argument
+ and stores it in the <code>fileName</code> variable:</p>
+
+ <source>if (args.length != 1)
+{
+ System.err.println("Usage: " + WriteTitle.class.getName() +
+ "destinationPOIFS");
+ System.exit(1);
+}
+final String fileName = args[0];</source>
+
+ <p>Let's create a property set now. We cannot use the
+ <code>PropertySet</code> class, because it is read-only: It does not have
+ a constructor creating an empty property set, and it does not have any
+ methods to modify its contents. Instead use the class
+ <code>MutablePropertySet</code>. It is a subclass of
+ <code>PropertySet</code>, and its no-args constructor established an
+ empty property set which we will fill later.</p>
+
+ <source>final MutablePropertySet mps = new MutablePropertySet();</source>
+
+ <p>By the way, the <code>MutablePropertySet</code> class has another
+ constructor taking a <code>PropertySet</code> as parameter. It creates a
+ mutable copy of its parameter.</p>
+
+ <p>The <code>MutablePropertySet</code> created by the no-args constructor
+ is not really empty: It contains a single section without any
+ properties. We can either retrieve that section and fill it with
+ properties, or we can replace it by another section. Of course we can
+ also add further sections to the property set. The sample application
+ decides to retrieve the section being already there:</p>
+
+ <source>final MutableSection ms = (MutableSection) mps.getSections().get(0);</source>
+
+ <p>The <code>getSections()</code> method returns the property set's
+ sections as a list, i.e. an instance of
+ <code>java.util.List</code>. Calling <code>get(0)</code> returns the
+ list's first (or zeroth if you prefer) element. It is a
+ <code>MutableSection</code>: a subclass of <code>Section</code> you can
+ modify.</p>
+
+ <p>Presently the <code>MutableSection</code> is still empty: It contains
+ no properties and does not have a format ID. As you have read in <link
+ href="#sec3">above</link> the format ID of the first section in a
+ property set determines the property set's type. If our property set
+ should become a summary information property set we have to set the
+ format ID of its first (and only) section to
+ <code>F29F85E0-4FF9-1068-AB-91-08-00-2B-27-B3-D9</code>. However, you
+ won't have to remember that ID if you want to write your own
+ summary information property sets: HPSF has it defined as the well-known
+ constant <code>Section.getFormatID()</code>. The sample application
+ writes it to the section with the <code>setFormatID(byte[])</code>
+ method.</p>
+
+ <source>ms.setFormatID(SectionIDMap.SUMMARY_INFORMATION_ID);</source>
+
+ <p>Now it is time to create a property. As you might expect there is a
+ subclass of <code>Property</code> called
+ <code>MutableProperty</code>.</p>
+
+ <source>final MutableProperty p = new MutableProperty();</source>
+
+ <p>A <code>MutableProperty</code> object must have an ID, a type, and a
+ value (see <link href="#sec3">above</link> for details). The class
+ provides methods to set these attributes:</p>
+
+ <source>p.setID(PropertyIDMap.PID_TITLE);
+p.setType(Variant.VT_LPWSTR);
+p.setValue("Sample title");</source>
+
+ <p>Now the sample property set is complete: We have a
+ <code>MutablePropertySet</code> containing a <code>MutableSection</code>
+ containing a <code>MutableProperty</code>. Of course we could have added
+ more sections and properties but we wanted to keep things simple.</p>
+
+ <p>The property set has to be written to a POI file system. The following
+ statement creates it.</p>
+
+ <source>final POIFSFileSystem poiFs = new POIFSFileSystem();</source>
+
+ <p>In order to write the property set to a POI file system it must be
+ converted into a sequence of bytes. The <code>MutablePropertySet</code>
+ class has a method <code>toInputStream()</code>. This method returns an
+ <code>InputStream</code> containing the bytes making out the property set
+ stream.</p>
+
+ <source>final InputStream is = mps.toInputStream();</source>
+
+ <p>If you'd read from this input stream you'd receive all these
+ bytes. However, it is very likely that you never do that. Instead you'll
+ pass the input stream to the <code>createDocument()</code> method of a
+ <code>POIFSFileSystem</code> instance, like the one we created a few
+ lines ago. Besides an <code>InputStream</code> the
+ <code>createDocument()</code> method takes another parameter: the name of
+ the document to be created. For a summary information property set stream
+ the default name is available as
+ <code>SummaryInformation.DEFAULT_STREAM_NAME</code>:</p>
+
+ <source>poiFs.createDocument(is, SummaryInformation.DEFAULT_STREAM_NAME);</source>
+
+ <p>The last step is to write the POI file system to a disk file:</p>
+
+ <source>poiFs.writeFilesystem(new FileOutputStream(fileName));</source>
</section>
</section>
+
+
<section><title>Further Reading</title>
<p>There are still some aspects of HSPF left which are not covered by this
HOW-TO. You should dig into the Javadoc API documentation to learn
projects / poi.git / commitdiff