common/src/main/java/org/apache/abdera2/common/templates/CachingContext.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */
package org.apache.abdera2.common.templates;

import java.util.HashMap;
import java.util.Map;

import org.apache.abdera2.common.templates.AbstractContext;

/**
 * Abstract Context implementation that caches resolved values so that do not have to be resolved again
 */
@SuppressWarnings("unchecked")
public abstract class CachingContext extends AbstractContext {

    private static final long serialVersionUID = 8912954163958644811L;
    
    private Map<String, Object> cache = new HashMap<String, Object>();

    public <T> T resolve(String var) {
        T t = (T)cache.get(var);
        if (t == null) {
            t = (T)resolveActual(var);
            if (t != null)
                cache.put(var, t);
        }
        return t;
    }

    protected abstract <T> T resolveActual(String var);

    public void clear() {
        cache.clear();
    }
}