| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.openjpa.persistence.criteria; |
| |
| import java.util.List; |
| |
| import javax.persistence.criteria.Expression; |
| import javax.persistence.criteria.Selection; |
| |
| import org.apache.openjpa.persistence.util.ReservedWords; |
| |
| /** |
| * An item selected in the projection clause of Criteria query. |
| * Base implementation for all concrete expressions. |
| * |
| * @param <X> the type this term evaluates to |
| * |
| * @author Pinaki Poddar |
| * |
| * @since 2.0.0 |
| */ |
| abstract class SelectionImpl<X> implements Selection<X>, CriteriaExpression { |
| private final Class<X> _cls; |
| private String _alias; |
| private Boolean _autoAliased; |
| |
| /** |
| * Construct with the immutable type represented by this selection term. |
| */ |
| public SelectionImpl(Class<X> cls) { |
| _cls = cls; |
| } |
| |
| /** |
| * Gets the immutable type represented by this selection term. |
| */ |
| @Override |
| public Class<X> getJavaType() { |
| return _cls; |
| } |
| |
| /** |
| * Gets the alias set of this selection term. |
| */ |
| @Override |
| public String getAlias() { |
| return _alias; |
| } |
| |
| /** |
| * Sets the alias on this selection term. |
| * Alias can only be set once. |
| */ |
| @Override |
| public Selection<X> alias(String alias) { |
| assertValidName(alias); |
| if (isAliased()) |
| throw new IllegalStateException(this + " has been aliased to [" + _alias |
| + ". Can not alias again to " + alias); |
| _alias = alias; |
| _autoAliased = false; |
| return this; |
| } |
| |
| /** |
| * Sets the alias of this expression internally. Only valid if the expression is not aliased explicitly |
| * by calling {@linkplain #alias(String)}. |
| */ |
| void setAutoAlias(String alias) { |
| if (isAliased()) |
| throw new IllegalStateException(this + " has been aliased. Can not set alias internally"); |
| _alias = alias; |
| _autoAliased = true; |
| } |
| |
| /** |
| * Affirms if the alias of this expression is assigned automatically. |
| */ |
| boolean isAutoAliased() { |
| return _autoAliased == null ? true : _autoAliased.booleanValue(); |
| } |
| |
| /** |
| * Affirms if this expression has been assigned an alias by {@linkplain #alias(String)} method. |
| * An alias can be assigned also by internal implementation. |
| * @see #isAutoAliased() |
| */ |
| boolean isAliased() { |
| return Boolean.FALSE.equals(_autoAliased); |
| } |
| |
| /** |
| * Throws IllegalStateException because a selection term, by default, consists of single value. |
| */ |
| @Override |
| public List<Selection<?>> getCompoundSelectionItems() { |
| throw new IllegalStateException(this + " is not a compound selection"); |
| } |
| |
| /** |
| * Returns false because a selection term, by default, consists of single value. |
| */ |
| @Override |
| public boolean isCompoundSelection() { |
| return false; |
| } |
| |
| void assertValidName(String name) { |
| if (name == null || name.trim().length() == 0) |
| throw new IllegalArgumentException("empty name is invalid"); |
| if (ReservedWords.isKeyword(name)) |
| throw new IllegalArgumentException("reserved word " + name + " is not valid"); |
| Character ch = ReservedWords.hasSpecialCharacter(name); |
| if (ch != null) |
| throw new IllegalArgumentException(name + " contains reserved symbol " + ch); |
| } |
| |
| // ------------------------------------------------------------------------------------ |
| // Contract for CriteriaExpression implemented mostly as a no-op for easier derivation. |
| // ------------------------------------------------------------------------------------ |
| |
| @Override |
| public StringBuilder asValue(AliasContext q) { |
| throw new IllegalStateException(this.getClass().getSimpleName() + " can not be rendered as value"); |
| } |
| |
| @Override |
| public StringBuilder asVariable(AliasContext q) { |
| throw new IllegalStateException(this.getClass().getSimpleName() + " can not be rendered as variable"); |
| } |
| |
| @Override |
| public StringBuilder asProjection(AliasContext q) { |
| String as = (isAutoAliased() ? "" : " AS " + getAlias()); |
| return asValue(q).append(as); |
| } |
| |
| @Override |
| public void acceptVisit(CriteriaExpressionVisitor visitor) { |
| Expressions.acceptVisit(visitor, this, (Expression<?>[])null); |
| } |
| } |