//$Id: DerbyDialect.java 15159 2008-09-08 19:50:44Z [email protected] $
package org.hibernate.dialect;
import org.hibernate.Hibernate;
import org.hibernate.QueryException;
import org.hibernate.HibernateException;
import org.hibernate.engine.Mapping;
import org.hibernate.engine.SessionFactoryImplementor;
import org.hibernate.type.Type;
import org.hibernate.dialect.function.SQLFunction;
import org.hibernate.dialect.function.SQLFunctionTemplate;
import org.hibernate.dialect.function.DerbyConcatFunction;
import org.hibernate.id.TableHiLoGenerator;
import org.hibernate.sql.CaseFragment;
import org.hibernate.sql.DerbyCaseFragment;
import java.util.List;
import java.util.ArrayList;
/** *
* Hibernate Dialect for Cloudscape 10 - aka Derby. This implements both an
* override for the identity column generator as well as for the case statement
* issue documented at:
* http://www.jroller.com/comments/kenlars99/Weblog/cloudscape_soon_to_be_derby
*
* @author Simon Johnston
*/
public class DerbyDialect extends DB2Dialect {
public DerbyDialect() {
super();
registerFunction( "concat", new DerbyConcatFunction() );
registerFunction( "trim", new DerbyTrimFunctionEmulation() );
}
/**
* This is different in Cloudscape to DB2.
*/
public String getIdentityColumnString() {
return "not null generated always as identity"; //$NON-NLS-1
}
/**
* Return the case statement modified for Cloudscape.
*/
public CaseFragment createCaseFragment() {
return new DerbyCaseFragment();
}
public boolean dropConstraints() {
return true;
}
public Class getNativeIdentifierGeneratorClass() {
return TableHiLoGenerator.class;
}
public boolean supportsSequences() {
return false;
}
public boolean supportsLimit() {
return false;
}
public boolean supportsLimitOffset() {
return false;
}
public String getQuerySequencesString() {
return null ;
}
/**
* A specialized function template to emulate the ANSI trim function on Derby DB
* since it does not support the full trim specification. However, we cannot even
* fully emulate it because there is not standard 'replace' function either. :(
*/
public static class DerbyTrimFunctionEmulation implements SQLFunction {
private static final SQLFunction LEADING_SPACE_TRIM = new SQLFunctionTemplate( Hibernate.STRING, "ltrim( ?1 )");
private static final SQLFunction TRAILING_SPACE_TRIM = new SQLFunctionTemplate( Hibernate.STRING, "rtrim( ?1 )");
private static final SQLFunction BOTH_SPACE_TRIM = new SQLFunctionTemplate( Hibernate.STRING, "ltrim( rtrim( ?1 ) )");
private static final SQLFunction BOTH_SPACE_TRIM_FROM = new SQLFunctionTemplate( Hibernate.STRING, "ltrim( rtrim( ?2 ) )");
public Type getReturnType(Type columnType, Mapping mapping) throws QueryException {
return Hibernate.STRING;
}
public boolean hasArguments() {
return true;
}
public boolean hasParenthesesIfNoArguments() {
return false;
}
public String render(List args, SessionFactoryImplementor factory) throws QueryException {
// according to both the ANSI-SQL and EJB3 specs, trim can either take
// exactly one parameter or a variable number of parameters between 1 and 4.
// from the SQL spec:
//
// <trim function> ::=
// TRIM <left paren> <trim operands> <right paren>
//
// <trim operands> ::=
// [ [ <trim specification> ] [ <trim character> ] FROM ] <trim source>
//
// <trim specification> ::=
// LEADING
// | TRAILING
// | BOTH
//
// If only <trim specification> is omitted, BOTH is assumed;
// if <trim character> is omitted, space is assumed
if ( args.size() == 1 ) {
// we have the form: trim(trimSource)
// so we trim leading and trailing spaces
return BOTH_SPACE_TRIM.render( args, factory );
}
else if ( "from".equalsIgnoreCase( ( String ) args.get( 0 ) ) ) {
// we have the form: trim(from trimSource).
// This is functionally equivalent to trim(trimSource)
return BOTH_SPACE_TRIM_FROM.render( args, factory );
}
else {
// otherwise, a trim-specification and/or a trim-character
// have been specified; we need to decide which options
// are present and "do the right thing"
boolean leading = true; // should leading trim-characters be trimmed?
boolean trailing = true; // should trailing trim-characters be trimmed?
String trimCharacter; // the trim-character
String trimSource; // the trim-source
// potentialTrimCharacterArgIndex = 1 assumes that a
// trim-specification has been specified. we handle the
// exception to that explicitly
int potentialTrimCharacterArgIndex = 1;
String firstArg = ( String ) args.get( 0 );
if ( "leading".equalsIgnoreCase( firstArg ) ) {
trailing = false;
}
else if ( "trailing".equalsIgnoreCase( firstArg ) ) {
leading = false;
}
else if ( "both".equalsIgnoreCase( firstArg ) ) {
}
else {
potentialTrimCharacterArgIndex = 0;
}
String potentialTrimCharacter = ( String ) args.get( potentialTrimCharacterArgIndex );
if ( "from".equalsIgnoreCase( potentialTrimCharacter ) ) {
trimCharacter = "' '";
trimSource = ( String ) args.get( potentialTrimCharacterArgIndex + 1 );
}
else if ( potentialTrimCharacterArgIndex + 1 >= args.size() ) {
trimCharacter = "' '";
trimSource = potentialTrimCharacter;
}
else {
trimCharacter = potentialTrimCharacter;
if ( "from".equalsIgnoreCase( ( String ) args.get( potentialTrimCharacterArgIndex + 1 ) ) ) {
trimSource = ( String ) args.get( potentialTrimCharacterArgIndex + 2 );
}
else {
trimSource = ( String ) args.get( potentialTrimCharacterArgIndex + 1 );
}
}
List argsToUse = new ArrayList();
argsToUse.add( trimSource );
argsToUse.add( trimCharacter );
if ( trimCharacter.equals( "' '" ) ) {
if ( leading && trailing ) {
return BOTH_SPACE_TRIM.render( argsToUse, factory );
}
else if ( leading ) {
return LEADING_SPACE_TRIM.render( argsToUse, factory );
}
else {
return TRAILING_SPACE_TRIM.render( argsToUse, factory );
}
}
else {
throw new HibernateException( "cannot specify trim character when using Derby as Derby does not support the ANSI trim function, not does it support a replace function to properly emmulate it" );
}
}
}
}
// Overridden informational metadata ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
public boolean supportsLobValueChangePropogation() {
return false;
}
}
|