Hello!
I am working on a project where various application data is initially read in
from XML files. This data may later be updated through a remote connection. Via
another remote connection, the data is made available to another computer that
does further processing. Basically we have several sources that need to be
managed. Therefore it is desirable to have a database storing and managing all
this data. We decided to try the object-oriented database db4o (www.db4o.com).
XML processing (as validation is a must!) is currently done with XMLBeans. It
is very handy as we don't have to manually create the 66 classes for all of our
3 Schemas.
I searched the db4o forum and already found out that someone has had problems
with XMLBeans. I also ran into a few, but managed to do some workarounds for
them. Still there remains a fundamental problem that just makes the use of
XMLBeans terribly inefficient in combination with db4o.
I am talking about a (probably xmlbeans-induced) database file size increase of
about 30 times compared to a simple example. I'd like to know if anyone can
give me some advice on what best to do.
Consider the following code, where i rebuilt the db4o Pilot example with
XMLBeans (class PilotType, let's call them PilotBeans):
public static void main(String[] args) {
Db4o.configure().exceptionsOnNotStorable(true);
String databaseFilename = new
String("Z:\\SVN\\tests\\db4o\\TestSimplePilot.db4o");
String databaseFilenameXB = new
String("Z:\\SVN\\tests\\db4o\\TestXmlBeanPilot.db4o");
ObjectContainer _db=Db4o.openFile(databaseFilename);
try {
clearDatabase(_db);
System.out.print("Storing simple Objects...\n");
for(int i=0; i<1000; ++i) {
_db.set(new Pilot("Michael Schumacher",100));
_db.set(new Pilot("Rubens Barrichello",99));
}
retrieveComplexNQ(_db);
}
finally {
_db.close();
}
ObjectContainer _dbt=Db4o.openFile(databaseFilenameXB);
try {
clearDatabaseXB(_dbt);
System.out.print("Storing XmlBean Objects...\n");
for(int i=0; i<1000; ++i) {
PilotType michi = PilotType.Factory.newInstance();
PilotType rubi = PilotType.Factory.newInstance();
michi.setFirstName("Michael");
michi.setLastName("Schumacher");
michi.setPoints(new BigInteger("100"));
rubi.setFirstName("Rubens");
rubi.setLastName("Barrichello");
rubi.setPoints(new BigInteger("99"));
_dbt.set(michi);
_dbt.set(rubi);
}
retrieveComplexNQxB(_dbt);
}
finally {
_dbt.close();
}
}
The Schema for the PilotBeans looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<schema targetNamespace="testPeter" xmlns="http://www.w3.org/2001/XMLSchema";
elementFormDefault="qualified" attributeFormDefault="unqualified">
<import namespace="http://www.w3.org/XML/1998/namespace";
schemaLocation="../ext_schema/xml.xsd"/>
<complexType name="PilotType">
<attribute name="firstName" type="string" use="required"/>
<attribute name="lastName" type="string" use="required"/>
<attribute name="points" type="integer" use="required" />
</complexType>
</schema>
The Pilot class is even simpler, as it doesn't distinguish between first and
last name. But that should'nt have a big impact. The code for the PilotBeans is
created with scomp from XmlBeans 2.2.0.
In both ways I end up with a database containing 2000 objects of Pilots or
PilotBeans. But the database containing the PilotBeans stores several other
objects that come with XmlBeans (probably the Schematype?) creating a massive
overhead. The file sizes are:
TestSimplePilot.db4o 176 KB
TestXmlBeanPilot.db4o 5700 KB
This increase is unreasonable big. In the case for our actual project some 100
XML files with total size of only 1.5 MB created a 3 GB (!) db4o database
file!!!
Does maybe anyone know a solution for this? I can only think of either dropping
XmlBeans and using another parser / my own classes to represent and store the
XML data in db4o. Or have a try with native XML databases. Has anyone had
experiences with XmlBeans and databases?
Thanks for any replies,
cheers,
Peter
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