| /* |
| * 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.kernel.exps; |
| |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.Iterator; |
| import java.util.Map; |
| |
| import org.apache.openjpa.kernel.StoreContext; |
| import org.apache.openjpa.meta.ClassMetaData; |
| |
| /** |
| * An in-memory representation of a {@link Value}. |
| * |
| * @author Abe White |
| * @nojavadoc |
| */ |
| public abstract class Val |
| implements Value { |
| |
| private ClassMetaData _meta = null; |
| |
| /** |
| * Return this value as a projection on the given candidate. |
| */ |
| public final Object evaluate(Object candidate, Object orig, |
| StoreContext ctx, Object[] params) { |
| try { |
| return eval(candidate, candidate, ctx, params); |
| } catch (NullPointerException npe) { |
| return null; |
| } catch (ClassCastException cce) { |
| return null; |
| } |
| } |
| |
| /** |
| * Return this value as an aggregate projection on the given group |
| * of candidates. |
| */ |
| public final Object evaluate(Collection candidates, Object orig, |
| StoreContext ctx, Object[] params) { |
| try { |
| Collection c = eval(candidates, orig, ctx, params); |
| if (c.isEmpty()) |
| return null; |
| return c.iterator().next(); |
| } catch (NullPointerException npe) { |
| return null; |
| } catch (ClassCastException cce) { |
| return null; |
| } |
| } |
| |
| /** |
| * Return this value for the given candidate. |
| */ |
| protected abstract Object eval(Object candidate, Object orig, |
| StoreContext ctx, Object[] params); |
| |
| /** |
| * Return a list of values resulting from evaluating each given |
| * candidate. By default, this implementation invokes |
| * {@link #eval(Object,Object,StoreContext,Map)} for |
| * each instance and packs the return value into a new list. Aggregates |
| * should override. |
| */ |
| protected Collection eval(Collection candidates, Object orig, |
| StoreContext ctx, Object[] params) { |
| Collection ret = new ArrayList(candidates.size()); |
| Object candidate; |
| for (Iterator itr = candidates.iterator(); itr.hasNext();) { |
| candidate = itr.next(); |
| ret.add(evaluate(candidate, (orig == null) ? candidate : orig, |
| ctx, params)); |
| } |
| return ret; |
| } |
| |
| public ClassMetaData getMetaData() { |
| return _meta; |
| } |
| |
| public void setMetaData(ClassMetaData meta) { |
| _meta = meta; |
| } |
| |
| public boolean isVariable() { |
| return false; |
| } |
| |
| public boolean isAggregate() { |
| return false; |
| } |
| |
| public boolean isXPath() { |
| return false; |
| } |
| |
| public void acceptVisit(ExpressionVisitor visitor) { |
| visitor.enter(this); |
| visitor.exit(this); |
| } |
| } |