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// This Source Code is in the Public Domain per: http://litesoft.org/License.txt package org.litesoft.orsup.base; import java.util.*; import org.litesoft.core.simpletypes.nonpublic.*; import org.litesoft.orsup.selection.*; /** * This class supports sorting of Persistent Objects in memory similar to the SQL's "ORDER BY" clause. * <p/> * Since the ordering of "null" values in SQL is unspecified, it has been decided * for "ASCending" to place them first, and * for "DESCending" to place them last. */ public class POOrderBy { public static class Result { public static final Result NULL = new Result( null ); private final Comparator<PersistentObject<?>> mComparator; public Result( Comparator<PersistentObject<?>> pComparator ) { mComparator = pComparator; } public Comparator<PersistentObject<?>> getComparator() { return mComparator; } } public static Result getComparator( MetaDataForPO pMD, OrderBy pOrderByClause ) { if ( (pOrderByClause == null) ) { return Result.NULL; } if ( isAcceptable( pMD, pOrderByClause ) ) { return new Result( createComparator( pMD, pOrderByClause ) ); } return null; } private static boolean isAcceptable( MetaDataForPO pMD, OrderBy pOrderByClause ) { AttributeAccessorSCD scd = pMD.getAccessorSCDoptional( pOrderByClause.getColumnDefinition().getName() ); if ( (scd != null) && scd.isPersisted() && SupplimentedSCD.Form.Local.equals( scd.getForm() ) && scd.isColumnTypeComparable() ) { OrderBy zSubOrderBy = pOrderByClause.getSubOrderBy(); return (zSubOrderBy == null) || isAcceptable( pMD, zSubOrderBy ); } return false; } private static MyComparator createComparator( MetaDataForPO pMD, OrderBy pOrderByClause ) { if ( pOrderByClause == null ) { return null; } AttributeAccessorSCD scd = pMD.getAccessorSCDrequired( pOrderByClause.getColumnDefinition().getName() ); return new MyComparator( pMD.getPOregistrationName(), scd, pOrderByClause.isDescending(), createComparator( pMD, pOrderByClause.getSubOrderBy() ) ); } private static class MyComparator implements Comparator<PersistentObject<?>> { private String mPORegisteredName; private AttributeAccessorSCD mSCD; private boolean mDecending; private MyComparator mSubComparator; public MyComparator( String pPORegisteredName, AttributeAccessorSCD pSCD, boolean pDecending, MyComparator pSubComparator ) { mPORegisteredName = pPORegisteredName; mSCD = pSCD; mDecending = pDecending; mSubComparator = pSubComparator; } private void chkType( PersistentObject<?> pPO ) { if ( !mPORegisteredName.equals( pPO.getRegisteredName() ) ) { throw new ClassCastException( "PO type: '" + pPO.getRegisteredName() + // "' != '" + mPORegisteredName + "'" ); } } @SuppressWarnings({"unchecked"}) private Comparable getValueOnPO( PersistentObject<?> pPO ) { return (Comparable) mSCD.getValueOnPO( pPO ); } @Override public int compare( PersistentObject<?> pPO1, PersistentObject<?> pPO2 ) { if ( pPO1.equals( pPO2 ) ) { return 0; } chkType( pPO1 ); chkType( pPO2 ); return LLcompare( pPO1, pPO2 ); } private int LLcompare( PersistentObject<?> pPO1, PersistentObject<?> pPO2 ) { int i = CompareSupport.compare( getValueOnPO( pPO1 ), getValueOnPO( pPO2 ) ); if ( i != 0 ) { return mDecending ? -i : i; } return (mSubComparator == null) ? 0 : mSubComparator.LLcompare( pPO1, pPO2 ); } } } |