| Hard coded database plattforms... [message #376328] |
Wed, 09 July 2008 20:49  |
 Michael Seidel
Messages: 12
Registered: July 2009 |
Junior Member |
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Hi,
Are there any plans to make the database support more configurable,
extensible? I just wanted to try EclipseLink with
the H2-Database (see: www.h2database.com) and had to use the HSQL Dialect
(no sequence support), because H2
is not supported by EclipseLink.
First thought was to write a support for the H2 database on my own.
Unfortunately all the database plattform identifier
are hard coded into internal classes in EclipseLink! I couldn't believe it,
but there is really one method for each supported
database in the abstract class
org.eclipse.persistence.internal.databaseaccess.Platform
Why don't you use any kind of factory and configure it from a file or let
the user name the plattform used within the
persistence.xml. In Hibernate there is a property for the persistence.xml,
which specifies the database dialect to use and
everybody can extend it, if needed. Of course, I can use the following
property
<property name="eclipselink.target-database" value="HSQL" />
but have no chance, if there is no build-in support for a database.
What about a property with the classified name of a Plattform-Implementation
to be used?
<property name="eclipselink.target-plattform"
value="org.eclipse.persistence.platform.database.HSQLPlatform " />
Regards,
Michael
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| Re: Hard coded database plattforms... [message #376343 is a reply to message #376330] |
Sat, 12 July 2008 19:15  |
Michael Seidel
Messages: 12
Registered: July 2009 |
Junior Member |
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This is a multi-part message in MIME format.
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Hi Doug,
thanks for the hint. I extended the HSQLPlatform (see attachment) and tried
it with your Geodata example.
Works fine. ;-)
Michael
"Doug Clarke" <douglas.clarke@oracle.com> schrieb im Newsbeitrag
news:851a1b27a0adf12154655151e107903c$1@www.eclipse.org...
> Michael,
>
> In earlier versions of TopLink we always made the developer provide the
> fully qualified platform name. We added the TargetDatabase enum with short
> values to simplify things. If you do write your own platform you can still
> specify it by providing the fully qualified class name in the value of the
> property:
>
> <property name="eclipselink.target-database"
> value="mypackage.MyH2Platform" />
>
> If you wish to contribute your H2 platform to the project please attach it
> to a bug and we'll do our best to get it in the next release.
>
> Doug
>
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Content-Type: application/octet-stream;
name="H2Platform.java"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
filename="H2Platform.java"
package org.eclipse.persistence.platform.database;
import java.io.IOException;
import java.io.Writer;
import java.util.Hashtable;
import org.eclipse.persistence.expressions.ExpressionOperator;
import =
org.eclipse.persistence.internal.databaseaccess.FieldTypeDef inition;
import org.eclipse.persistence.queries.ValueReadQuery;
import org.eclipse.persistence.sequencing.NativeSequence;
import org.eclipse.persistence.sequencing.Sequence;
public class H2Platform extends HSQLPlatform {
private static final long serialVersionUID =3D =
-2935483687958482934L;
public H2Platform() {
super();
setPingSQL("CALL 42");
setSupportsAutoCommit(true);
setUsesBatchWriting(true);
}
@Override
public final boolean isHSQL() {
return false;
}
@Override
@SuppressWarnings("unchecked")
protected Hashtable buildFieldTypes() {
Hashtable fieldTypeMapping =3D super.buildFieldTypes();
fieldTypeMapping.put(java.sql.Date.class, new =
FieldTypeDefinition("DATE", false));
fieldTypeMapping.put(java.sql.Time.class, new =
FieldTypeDefinition("TIME", false));
fieldTypeMapping.put(java.sql.Timestamp.class, new =
FieldTypeDefinition("TIMESTAMP", false));
return fieldTypeMapping;
}
@Override
public ValueReadQuery buildSelectQueryForSequenceObject(String =
seqName, Integer size) {
return new ValueReadQuery(new StringBuilder(20 + seqName.length())
.append("CALL NEXT VALUE FOR ").append(seqName).toString());
}
@Override
public Writer buildSequenceObjectAlterIncrementWriter(Writer writer, =
String fullSeqName, int increment) throws IOException {
return writer.append("ALTER SEQUENCE ").append(fullSeqName)
.append(" INCREMENT BY ").append(Integer.toString(increment));
}
@Override
public Writer buildSequenceObjectCreationWriter(Writer writer, =
String fullSeqName, int increment, int start) throws IOException {
return writer.append("CREATE SEQUENCE IF NOT EXISTS =
").append(fullSeqName)
.append(" START WITH ").append(Integer.toString(start)).append(" =
INCREMENT BY ")
.append(Integer.toString(increment));
}
@Override
protected Sequence createPlatformDefaultSequence() {
return new NativeSequence();
}
@Override
public boolean isAlterSequenceObjectSupported() {
return true;
}
@Override
public boolean supportsForeignKeyConstraints() {
return true;
}
@Override
public boolean supportsLocalTempTables() {
return true;
}
@Override
public boolean supportsGlobalTempTables() {
return true;
}
@Override
public boolean supportsNativeSequenceNumbers() {
return true;
}
@Override
public boolean supportsStoredFunctions() {
return true;
}
@Override
public ValueReadQuery getTimestampQuery() {
return new ValueReadQuery("SELECT CURRENT_TIMESTAMP()");
}
@Override
protected void initializePlatformOperators() {
super.initializePlatformOperators();
addOperator(ExpressionOperator.simpleMath(ExpressionOperator .Concat, =
"||"));
}
}
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