/*
* Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
*
* Licensed 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.activiti.engine.impl.juel;
/**
* Tree store class.
* A tree store holds a {@link org.activiti.engine.impl.juel.TreeBuilder} and a
* {@link org.activiti.engine.impl.juel.TreeCache}, provided at construction time.
* The <code>get(String)</code> method is then used to serve expression trees.
*
* @author Christoph Beck
*/
public class TreeStore {
private final TreeCache cache;
private final TreeBuilder builder;
/**
* Constructor.
* @param builder the tree builder
* @param cache the tree cache (may be <code>null</code>)
*/
public TreeStore(TreeBuilder builder, TreeCache cache) {
super();
this.builder = builder;
this.cache = cache;
}
public TreeBuilder getBuilder() {
return builder;
}
/**
* Get a {@link Tree}.
* If a tree for the given expression is present in the cache, it is
* taken from there; otherwise, the expression string is parsed and
* the resulting tree is added to the cache.
* @param expression expression string
* @return expression tree
*/
public Tree get(String expression) throws TreeBuilderException {
if (cache == null) {
return builder.build(expression);
}
Tree tree = cache.get(expression);
if (tree == null) {
cache.put(expression, tree = builder.build(expression));
}
return tree;
}
}