how-to.xml.orig

Office格式转换代码

                    structures.  Its relatively simple to use, but requires a basic
                    understanding of the parts of an Excel file (or willingness to
                    learn).  The advantage provided is that you can read an XLS with a
                    relatively small memory footprint.
                    </p>
                    <p>To use this API you construct an instance of
                    org.apache.poi.hssf.eventmodel.HSSFRequest. Register a class you
                    create that supports the
                    org.apache.poi.hssf.eventmodel.HSSFListener interface using the
                    HSSFRequest.addListener(yourlistener, recordsid).  The recordsid
                    should be a static reference number (such as BOFRecord.sid) contained
                    in the classes in org.apache.poi.hssf.record.  The trick is you
                    have to know what these records are.  Alternatively you can call
                    HSSFRequest.addListenerForAllRecords(mylistener).  In order to learn
                    about these records you can either read all of the javadoc in the
                    org.apache.poi.hssf.record package or you can just hack up a
                    copy of org.apache.poi.hssf.dev.EFHSSF and adapt it to your
                    needs.  TODO: better documentation on records.</p>
                    <p>Once you've registered your listeners in the HSSFRequest object
                    you can construct an instance of
                    org.apache.poi.poifs.filesystem.FileSystem (see POIFS howto) and
                    pass it your XLS file inputstream.  You can either pass this, along
                    with the request you constructed, to an instance of HSSFEventFactory
                    via the HSSFEventFactory.processWorkbookEvents(request, Filesystem)
                    method, or you can get an instance of DocumentInputStream from
                    Filesystem.createDocumentInputStream(&quot;Workbook&quot;) and pass
                    it to HSSFEventFactory.processEvents(request, inputStream).  Once you
                    make this call, the listeners that you constructed receive calls to
                    their processRecord(Record) methods with each Record they are
                    registered to listen for until the file has been completely read.
                    </p>
                    <p>A code excerpt from org.apache.poi.hssf.dev.EFHSSF (which is
                    in CVS or the source distribution) is reprinted below with excessive
                    comments:</p>
<source><![CDATA[
/**
 * This example shows how to use the event API for reading a file.
 */
public class EventExample
        implements HSSFListener
{
    private SSTRecord sstrec;

    /**
     * This method listens for incoming records and handles them as required.
     * @param record    The record that was found while reading.
     */
    public void processRecord(Record record)
    {
        switch (record.getSid())
        {
            // the BOFRecord can represent either the beginning of a sheet or the workbook
            case BOFRecord.sid:
                BOFRecord bof = (BOFRecord) record;
                if (bof.getType() == bof.TYPE_WORKBOOK)
                {
                    System.out.println("Encountered workbook");
                    // assigned to the class level member
                } else if (bof.getType() == bof.TYPE_WORKSHEET)
                {
                    System.out.println("Encountered sheet reference");
                }
                break;
            case BoundSheetRecord.sid:
                BoundSheetRecord bsr = (BoundSheetRecord) record;
                System.out.println("New sheet named: " + bsr.getSheetname());
                break;
            case RowRecord.sid:
                RowRecord rowrec = (RowRecord) record;
                System.out.println("Row found, first column at "
                        + rowrec.getFirstCol() + " last column at " + rowrec.getLastCol());
                break;
            case NumberRecord.sid:
                NumberRecord numrec = (NumberRecord) record;
                System.out.println("Cell found with value " + numrec.getValue()
                        + " at row " + numrec.getRow() + " and column " + numrec.getColumn());
                break;
                // SSTRecords store a array of unique strings used in Excel.
            case SSTRecord.sid:
                sstrec = (SSTRecord) record;
                for (int k = 0; k < sstrec.getNumUniqueStrings(); k++)
                {
                    System.out.println("String table value " + k + " = " + sstrec.getString(k));
                }
                break;
            case LabelSSTRecord.sid:
                LabelSSTRecord lrec = (LabelSSTRecord) record;
                System.out.println("String cell found with value "
                        + sstrec.getString(lrec.getSSTIndex()));
                break;
        }
    }

    /**
     * Read an excel file and spit out what we find.
     *
     * @param args      Expect one argument that is the file to read.
     * @throws IOException  When there is an error processing the file.
     */
    public static void main(String[] args) throws IOException
    {
        // create a new file input stream with the input file specified
        // at the command line
        FileInputStream fin = new FileInputStream(args[0]);
        // create a new org.apache.poi.poifs.filesystem.Filesystem
        POIFSFileSystem poifs = new POIFSFileSystem(fin);
        // get the Workbook (excel part) stream in a InputStream
        InputStream din = poifs.createDocumentInputStream("Workbook");
        // construct out HSSFRequest object
        HSSFRequest req = new HSSFRequest();
        // lazy listen for ALL records with the listener shown above
        req.addListenerForAllRecords(new EventExample());
        // create our event factory
        HSSFEventFactory factory = new HSSFEventFactory();
        // process our events based on the document input stream
        factory.processEvents(req, din);
        // once all the events are processed close our file input stream
        fin.close();
        // and our document input stream (don't want to leak these!)
        din.close();
        System.out.println("done.");
    }
}
]]></source>
     </section>
                <section><title>Low Level APIs</title>

<p>The low level API is not much to look at. It consists of lots of
&quot;Records&quot; in the org.apache.poi.hssf.record.* package,
and set of helper classes in org.apache.poi.hssf.model.*. The
record classes are consistent with the low level binary structures
inside a BIFF8 file (which is embedded in a POIFS file system). You
probably need the book: &quot;Microsoft Excel 97 Developer's Kit&quot;
from Microsoft Press in order to understand how these fit together
(out of print but easily obtainable from Amazon's used books). In
order to gain a good understanding of how to use the low level APIs
should view the source in org.apache.poi.hssf.usermodel.* and
the classes in org.apache.poi.hssf.model.*. You should read the
documentation for the POIFS libraries as well.</p>
     </section>
                <section><title>HSSF Class/Test Application</title>

<p>The HSSF application is nothing more than a test for the high
level API (and indirectly the low level support). The main body of
its code is repeated above. To run it:
</p>
<ul>
    <li>download the poi-alpha build and untar it (tar xvzf
    tarball.tar.gz)
    </li>
    <li>set up your classpath as follows:
    <code>export HSSFDIR={wherever you put HSSF's jar files}
export LOG4JDIR={wherever you put LOG4J's jar files}
export CLASSPATH=$CLASSPATH:$HSSFDIR/hssf.jar:$HSSFDIR/poi-poifs.jar:$HSSFDIR/poi-util.jar:$LOG4JDIR/jog4j.jar</code>
    </li><li>type:
    <code>java org.apache.poi.hssf.dev.HSSF ~/myxls.xls write</code></li>
</ul>
<p></p>
<p>This should generate a test sheet in your home directory called <code>&quot;myxls.xls&quot;</code>.  </p>
<ul>
    <li>Type:
    <code>java org.apache.poi.hssf.dev.HSSF ~/input.xls output.xls</code>
    <br/>
    <br/>
This is the read/write/modify test.  It reads in the spreadsheet, modifies a cell, and writes it back out.
Failing this test is not necessarily a bad thing.  If HSSF tries to modify a non-existant sheet then this will
most likely fail.  No big deal.  </li>
</ul>
     </section>
    <section><title>Logging facility</title>
        <p>Poi can dynamically select it's logging implementation. Poi trys to
        create a logger using the System property named "org.apache.poi.util.POILogger".
        Out of the box this can be set to one of three values:
        </p>
        <ul>
           <li>org.apache.poi.util.CommonsLogger</li>
           <li>org.apache.poi.util.NullLogger</li>
           <li>org.apache.poi.util.SystemOutLogger</li>
        </ul>
        <p>
        If the property is not defined or points to an invalid classthen the NullLogger is used.
        </p>
        <p>
        Refer to the commons logging package level javadoc for more information concerning how to
        <link href="http://jakarta.apache.org/commons/logging/api/index.html">configure commons logging.</link>
        </p>
     </section>
    <section><title>HSSF Developer's Tools</title>

<p>HSSF has a number of tools useful for developers to debug/develop
stuff using HSSF (and more generally XLS files). We've already
discussed the app for testing HSSF read/write/modify capabilities;
now we'll talk a bit about BiffViewer. Early on in the development of
HSSF, it was decided that knowing what was in a record, what was
wrong with it, etc. was virtually impossible with the available
tools. So we developed BiffViewer. You can find it at
org.apache.poi.hssf.dev.BiffViewer. It performs two basic
functions and a derivative.
</p>
<p>The first is &quot;biffview&quot;. To do this you run it (assumes
you have everything setup in your classpath and that you know what
you're doing enough to be thinking about this) with an xls file as a
parameter. It will give you a listing of all understood records with
their data and a list of not-yet-understood records with no data
(because it doesn't know how to interpret them). This listing is
useful for several things. First, you can look at the values and SEE
what is wrong in quasi-English. Second, you can send the output to a
file and compare it.
</p>
<p>The second function is &quot;big freakin dump&quot;, just pass a
file and a second argument matching &quot;bfd&quot; exactly. This
will just make a big hexdump of the file.
</p>
<p>Lastly, there is &quot;mixed&quot; mode which does the same as
regular biffview, only it includes hex dumps of certain records
intertwined. To use that just pass a file with a second argument
matching &quot;on&quot; exactly.</p>
<p>In the next release cycle we'll also have something called a
FormulaViewer. The class is already there, but its not very useful
yet. When it does something, we'll document it.</p>

     </section>
                <section><title>What's Next?</title>

<p>This release contains code that supports &quot;internationalization&quot;
or more accurately non-US/UK languages; however, it has not been
tested with the new API changes (please help us with this). We've
shifted focus a bit for this release in recognition of the
international support we've gotten. We're going to focus on western
European languages for our first beta. We're more than happy to
accept help in supporting non-Western European languages if someone
who knows what they're doing in this area is willing to pitch in!
(There is next to no documentation on what is necessary to support
such a move and its really hard to support a language when you don't even
know the alphabet).</p>
<p>This release of HSSF does not yet support Formulas. I've been
focusing on the requests I've gotten in. That being said, if we get
more user feedback on what is most useful first we'll aim for that.
As a general principal, HSSF's goal is to support HSSF-Serializer
(meaning an emphasis on write). We would like to hear from you! How
are you using HSSF/POIFS? How would you like to use it? What features
are most important first?
</p>
     </section>

</section>

</section>
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