/* 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.persistence.deploy;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Default cache: keep everything in memory, unless a limit is set.
 * 
 * @author Joram Barrez
 */
public class DefaultDeploymentCache<T> implements DeploymentCache<T> {
  
  private static final Logger logger = LoggerFactory.getLogger(DefaultDeploymentCache.class);
  
  protected Map<String, T> cache;
  
  /** Cache with no limit */
  public DefaultDeploymentCache() {
    this.cache = new HashMap<String, T>();
  }
  
  /** Cache which has a hard limit: no more elements will be cached than the limit. */
  public DefaultDeploymentCache(final int limit) {
    this.cache = new LinkedHashMap<String, T>(limit + 1, 0.75f, true) { // +1 is needed, because the entry is inserted first, before it is removed
                                                                       // 0.75 is the default (see javadocs)
                                                                       // true will keep the 'access-order', which is needed to have a real LRU cache
      private static final long serialVersionUID = 1L;

      protected boolean removeEldestEntry(java.util.Map.Entry<String, T> eldest) {
        boolean removeEldest = size() > limit;
        if (removeEldest) {
          logger.trace("Cache limit is reached, {} will be evicted",  eldest.getKey());
        }
        return removeEldest;
      }
      
    };
  }
  
  public T get(String id) {
    return cache.get(id);
  }
  
  public void add(String id, T obj) {
    cache.put(id, obj);
  }
  
  public void remove(String id) {
    cache.remove(id);
  }
  
  public void clear() {
    cache.clear();
  }
  
  // For testing purposes only
  public int size() {
    return cache.size();
  }
  
}

/* 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.persistence.deploy;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Default cache: keep everything in memory, unless a limit is set.
 * 
 * @author Joram Barrez
 */
public class DefaultDeploymentCache<T> implements DeploymentCache<T> {
  
  private static final Logger logger = LoggerFactory.getLogger(DefaultDeploymentCache.class);
  
  protected Map<String, T> cache;
  
  /** Cache with no limit */
  public DefaultDeploymentCache() {
    this.cache = new HashMap<String, T>();
  }
  
  /** Cache which has a hard limit: no more elements will be cached than the limit. */
  public DefaultDeploymentCache(final int limit) {
    this.cache = Collections.synchronizedMap(new LinkedHashMap<String, T>(limit + 1, 0.75f, true) { // +1 is needed, because the entry is inserted first, before it is removed
                                                                       // 0.75 is the default (see javadocs)
                                                                       // true will keep the 'access-order', which is needed to have a real LRU cache
      private static final long serialVersionUID = 1L;

      protected boolean removeEldestEntry(java.util.Map.Entry<String, T> eldest) {
        boolean removeEldest = size() > limit;
        if (removeEldest) {
          logger.trace("Cache limit is reached, {} will be evicted",  eldest.getKey());
        }
        return removeEldest;
      }
      
    });
  }
  
  public T get(String id) {
    return cache.get(id);
  }
  
  public void add(String id, T obj) {
    cache.put(id, obj);
  }
  
  public void remove(String id) {
    cache.remove(id);
  }
  
  public void clear() {
    cache.clear();
  }
  
  // For testing purposes only
  public int size() {
    return cache.size();
  }
  
}

Fix race condition in DefaultDeploymentCache (see http://forums.activiti.org/content/race-hazard-defaultdeploymentcache)