Examples of org.eclipse.persistence.expressions.Expression

Package org.eclipse.persistence.expressions

Examples of org.eclipse.persistence.expressions.Expression

org.eclipse.persistence.expressions.Expression
Purpose: Define an object-level representation of a database query where clause.

Description: An expression is a tree-like structure that defines the selection criteria for a query against objects in the database. The expression has the advantage over SQL by being at the object-level, i.e. the object model attributes and relationships can be used to be query on instead of the database field names. Because it is an object, not a string the expression has the advantage that is can be easily manipulated through code to easily build complex selection criterias.

Responsibilities:
- Store the selection criteria in a tree-like structure.
- Support public manipulation protocols for all comparison and function operators.
- Use opperator overloading to support all primitive types as well as objects.

            if ((queryClass != null) && (queryClass != getReferenceClass())) {
                return getSession().getDescriptor(queryClass);
            }
            return rootDescriptor;
        }
        Expression baseExpression = ((QueryKeyExpression)expression).getBaseExpression();
        ClassDescriptor baseDescriptor = getLeafDescriptorFor(baseExpression, rootDescriptor);
        
        if (expression.isMapEntryExpression()){
            // get the expression that owns the mapping for the table entry
            Expression owningExpression = ((QueryKeyExpression)baseExpression).getBaseExpression();
            ClassDescriptor owningDescriptor = getLeafDescriptorFor(owningExpression, rootDescriptor);
            
            // Get the mapping that owns the table
            CollectionMapping mapping = (CollectionMapping)owningDescriptor.getObjectBuilder().getMappingForAttributeName(baseExpression.getName());

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            localFields.addElement(getDescriptor().getInheritancePolicy().getClassIndicatorField());
        }


        //Add attribute fields
        for(Iterator it = getPartialAttributeExpressions().iterator();it.hasNext();){
            Expression expression = (Expression)it.next();
            if (expression.isQueryKeyExpression()) {
                ((QueryKeyExpression)expression).getBuilder().setSession(session.getRootSession(null));
                ((QueryKeyExpression)expression).getBuilder().setQueryClass(getDescriptor().getJavaClass());
                DatabaseMapping mapping = ((QueryKeyExpression)expression).getMapping();
                if (!((QueryKeyExpression)expression).getBaseExpression().isExpressionBuilder()) {
                    if(foreignFields==null){
                        foreignFields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance();
                    }
                    if(!isCustomSQL){
                        foreignFields.add(expression);
                    }else{
                        foreignFields.addAll(expression.getFields());
                    }
                }else{
                    if (mapping == null) {
                        throw QueryException.specifiedPartialAttributeDoesNotExist(this, expression.getName(), descriptor.getJavaClass().getName());
                    }
                    if(mapping.isForeignReferenceMapping() ){
                        if(foreignFields==null){
                            foreignFields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance();
                        }
                        if(!isCustomSQL){
                            foreignFields.add(expression);
                        }else{
                            foreignFields.addAll(expression.getFields());
                        }
                    }else{
                        localFields.addAll(expression.getFields());
                    }
                }
            } else {
                throw QueryException.expressionDoesNotSupportPartialAttributeReading(expression);
            }

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        }


        // Validate and prepare partial attribute expressions.
        if (hasPartialAttributeExpressions()) {
            for (int index = 0; index < getPartialAttributeExpressions().size(); index++) {
                Expression expression = getPartialAttributeExpressions().get(index);


                // Search if any of the expression traverse a 1-m.
                while (expression.isQueryKeyExpression() && (!expression.isExpressionBuilder())) {
                    if (((QueryKeyExpression)expression).shouldQueryToManyRelationship()) {
                      getJoinedAttributeManager().setIsToManyJoinQuery(true);
                    }
                    expression = ((QueryKeyExpression)expression).getBaseExpression();
                }

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     * Apply this node to the passed query
     */
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext generationContext) {
        if (theQuery instanceof ReportQuery) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            Expression expression = generateExpression(generationContext);
            reportQuery.addItem("NullIf(" + getLeft().getAsString() + "," + getRight().getAsString() + ")", expression);
        }
    }

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    /**
     * INTERNAL
     * Generate the a new EclipseLink NullIf expression for this node.
     */
    public Expression generateExpression(GenerationContext context) {
        Expression whereClause = getLeft().generateExpression(context).nullIf(getRight().generateExpression(context));
        return whereClause;
    }

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     * Apply this node to the passed query
     */
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext generationContext) {
        if (theQuery instanceof ReportQuery) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            Expression expression = generateExpression(generationContext);
            reportQuery.addItem(left.resolveAttribute() + " MapEntry", expression);
        }
    }

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    /**
     * INTERNAL
     * Generate the a new EclipseLink TableEntryExpression for this node.
     */
    public Expression generateExpression(GenerationContext context) {
        Expression owningExpression = getLeft().generateExpression(context);
        MapEntryExpression whereClause = new MapEntryExpression(owningExpression);
        whereClause.returnMapEntry();
        return whereClause;
    }

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     */
    public Expression generateExpression(GenerationContext context) {
        if (alias == null){
            alias = getAsString();
        }
        Expression aggregateExpr = context.expressionFor(alias);
        if (aggregateExpr == null) {
            Expression arg = getLeft().generateExpression(context);
            if (usesDistinct()) {
                arg = arg.distinct();
            }
            aggregateExpr = addAggregateExression(arg);
            context.addExpression(aggregateExpr, alias);
        }
        return aggregateExpr;

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     * Apply this node to the passed query
     */
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext generationContext) {
        if (theQuery instanceof ReportQuery) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            Expression expression = generateExpression(generationContext);
            reportQuery.addAttribute(left.resolveAttribute() + " Type", expression, Class.class);
        }
    }

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    /**
     * INTERNAL
     * Generate the a new EclipseLink TableEntryExpression for this node.
     */
    public Expression generateExpression(GenerationContext context) {
        Expression owningExpression = getLeft().generateExpression(context);
        
        return owningExpression.type();
    }

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Related Classes of org.eclipse.persistence.expressions.Expression

org.eclipse.persistence.descriptors.DescriptorQueryManager

org.eclipse.persistence.descriptors.SingleTableMultitenantPolicy

org.eclipse.persistence.eis.mappings.EISOneToManyMapping

org.eclipse.persistence.eis.mappings.EISOneToOneMapping

org.eclipse.persistence.expressions.spatial.SpatialExpressionFactory

org.eclipse.persistence.internal.descriptors.CascadeLockingPolicy

org.eclipse.persistence.internal.expressions.ClassTypeExpression

org.eclipse.persistence.internal.expressions.MapEntryExpression

org.eclipse.persistence.internal.expressions.OuterJoinExpressionHolder

org.eclipse.persistence.internal.expressions.SQLUpdateStatement

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