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<?xml version="1.0"?>
<faqs title="Frequently Asked Questions">
<part id="general">
<title>General</title>
<faq id="linux">
<question>Does this work on Linux/Unix?</question>
<answer>
<p>Yep, Jackcess is pure Java. It will work on any
Java Virtual Machine (1.4+).</p>
</answer>
</faq>
<faq id="formats">
<question>What Access formats does it support?</question>
<answer>
<p>Jackcess currently supports <i>only</i> Access 2000
databases. Access 2003 is not supported.</p>
</answer>
</faq>
<faq id="passwords">
<question>Are password protected databases supported?</question>
<answer>
<p>Basic password protection is merely software enforced, and Jackcess
does not do any password checking at this point. So, a password
protected database can be used the same as any other.</p>
</answer>
</faq>
<faq id="mdbtools">
<question>
How is this different from
<a href="http://mdbtools.sf.net">mdbtools</a>?
</question>
<answer>
<p>
We want to give a lot of credit to mdbtools. They have
been around much longer than Jackcess, and, along with
<a href="http://poi.apache.org/">POI</a>,
inspired us that a project like this could be done.
mdbtools is written in C. There is a Java port of it,
but if you've ever read or used a Java port of a C
library, you can appreciate the difference between such
a library and one written from scratch in Java.
</p>
<p>
At the time of this writing, mdbtools could only read
Access databases. Jackcess can also write to them.
According to their web site, "Write support is currently being
worked on and the first cut is expected to be included in the
0.6 release." This status hasn't changed since we first
started work on Jackcess.
</p>
<p>
mdbtools supports Access 97 databases, which Jackcess does not.
The Java port of mdbtools also includes an implementation of
a small subset of the JDBC APIs. Jackcess does not currently,
but a pure Java JDBC driver for Access could certainly be written
on top of Jackcess.
</p>
</answer>
</faq>
<faq id="poi">
<question>
This looks like a logical addition to POI. Why not integrate with
that project?
</question>
<answer>
<p>
<a href="http://poi.apache.org/">POI</a> is released under
<a href="http://www.apache.org/foundation/licence-FAQ.html">The Apache License</a>.
Jackcess is released under
<a href="http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt">The GNU Lesser General Public License</a>.
The Apache license allows closed-source and/or commercial forks.
The LGPL does not. If you change or enhance Jackcess, you must contribute
your changes back to the project.
</p>
</answer>
</faq>
<faq id="odbc">
<question>
I'm using the JDBC/ODBC bridge. Why should I try Jackcess?
</question>
<answer>
<p>
<ul>
<li>
Portability - With Jackcess, your app has one less dependency on Windows.
</li>
<li>
Speed - We had an app that used the ODBC bridge to write data to an
Access database. When we switched it over to use Jackcess, it was 5 times faster.
</li>
<li>
Stability - With large amounts of data, we found the ODBC brige to be
pretty unreliable.
</li>
<li>
Simplicity - With Jackcess, there is no ODBC configuration to set up.
</li>
</ul>
</p>
</answer>
</faq>
<faq id="jdk">
<question>What version of the JDK does this require?</question>
<answer>
<p>
Version 1.0 requires JDK 1.4 or higher. The version in SVN trunk
and all future releases will require JDK 1.5 or higher.
</p>
<p>
However, some users have contributed patches to make later versions
compatible with JDK 1.4. Please check the contributions/ directory
in the source repository for any such patches. Note that any code
in this directory is untested and unsupported, so please use at your
own risk and do not file bugs based on that code.
</p>
</answer>
</faq>
<faq id="dependencies">
<question>Why do I get a NoClassDefFoundError?</question>
<answer>
<p>
Probably because you're missing a jar that Jackcess depends on from
your classpath. Take a look at the <a href="dependencies.html">dependencies list</a>. The "compile" and
"runtime" dependencies are necessary for using Jackcess in your
application. One great place to track down these dependencies is in
the <a href="http://repo1.maven.org/maven2/">Ibiblio Maven
Repository</a>.
</p>
</answer>
</faq>
<faq id="speed">
<question>Why is jackcess so slow for large updates?</question>
<answer>
<p>
While there is much room for improvement in update speed, one factor
is whether or not all writes are automatically forced to disk. By
default, "autoSync" is enabled, which keeps the database file in a
more consistent state, but can be very slow for large updates.
Disabling "autoSync" can dramatically increase update speed, but
exceptions during update can leave the file in an unusable state.
So, modifying this option essentially trades off speed for
recoverability.
</p>
</answer>
</faq>
<faq id="international">
<question>Why am I getting an IOException with the message "unmapped
string index value"?</question>
<answer>
<p>
Update: As of the 1.1.21 release, the <u>text index handling
supports the entire Basic Multilingual Plane 0</u> (i.e. any unicode
character 0x0000-0xFFFF). Consequently table names can (as of this
release) contain any character in this character set. Therefore,
the rest of this answer should no longer be an issue, but keeping it
here for reference.
</p>
<p>
Jackcess cannot currently update a text column index with values
which contain non-ascii characters. This situation often arises
when tables are created with names which contain international
characters. Access stores the table names in another table which
has an index on the table name column. The index encoding is not
simple to reverse engineer, so it is not likely that Jackcess will
support this anytime soon.
</p>
<p>
Update: As of the 1.1.13 release, the text index handling supports
the entire ISO-8859-1 character set. Consequently table names can
(as of this release) contain any character in this character set.
</p>
<p>
Some suggestions (for older releases):
</p>
<ul>
<li>Use only ascii (or ISO-8859-1 as of 1.1.13) characters in table
names if at all possible</li>
<li>If tables with international characters are required, create the
tables using Access, then update the tables using jackcess.</li>
<li>For indexes on user created tables, populate the table without
indexes in jackcess, then add the index using Access.</li>
</ul>
</answer>
</faq>
<faq id="bigindex">
<question>Why am I getting an UnsupportedOperationException (or
IOException) when updating an indexed table?</question>
<answer>
Previously index update support only handled tables with small numbers
of rows. When the index size limit was reached an
UnsupportedOperationException (or possibly an IOException) was thrown.
As of the 1.1.14 release, experimental, optional large index support
has been added. This support is disabled by default but can be
enabled via a few different means. Please see the <a href="apidocs/com/healthmarketscience/jackcess/Database.html">Database javadocs</a>
for details on enabling large index support.
</answer>
</faq>
<faq id="query">
<question>Can Jackcess execute SQL queries?</question>
<answer>
As of the 1.1.19 release, Jackcess has the ability to <i>read</i> the
Queries saved in an Access database (i.e. interpret the data stored in
the system Queries table). However, Jackcess does not have the
ability to <i>execute</i> these Queries. There have been a few
attempts to use Jackcess to build JDBC drivers for Access databases,
but none of the projects seem to have progressed very far before
becoming inactive.
</answer>
</faq>
<faq id="hms">
<question>Who is Health Market Science?</question>
<answer>
<p>
HMS is a small company located in suburban Philadelphia.
Using proprietary matching and consolidation software,
HMS scientifically manufactures the most comprehensive
and accurate healthcare data sets in the market today.
<a href="http://www.healthmarketscience.com/company/careers.html">We're hiring!</a>
HMS is always looking for talented individuals.
</p>
</answer>
</faq>
<faq id="bugs">
<question>It doesn't work!</question>
<answer>
<p>
Ok, that wasn't a question, but we'll try to respond anyway. :)
Jackcess is young, and not that robust yet. As you might imagine,
it's kind of hard to test, simply by its nature. There are
bugs that we are aware of, and certainly many more that we are not.
If you find what looks like a bug, please
<a href="http://sf.net/tracker/?group_id=134943&atid=731445">report it.</a>
Even better, fix it, and
<a href="http://sf.net/tracker/?group_id=134943&atid=731447">submit a patch.</a>
</p>
</answer>
</faq>
</part>
</faqs>
|
