AbstractMetadataCache.java

package org.springframework.roo.metadata.internal;

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

import org.apache.commons.lang3.Validate;
import org.springframework.roo.metadata.MetadataCache;
import org.springframework.roo.metadata.MetadataIdentificationUtils;
import org.springframework.roo.metadata.MetadataItem;

/**
 * Basic {@link MetadataCache} that stores elements on a least recently used
 * (LRU) basis.
 * 
 * @author Ben Alex
 * @since 1.0
 */
public abstract class AbstractMetadataCache implements MetadataCache {

  private static final float hashTableLoadFactor = 0.75f;

  private LinkedHashMap<String, MetadataItem> map;
  private int maxCapacity = 100000;

  protected AbstractMetadataCache() {
    init();
  }

  public void evict(final String metadataIdentificationString) {
    Validate.isTrue(
        MetadataIdentificationUtils.isIdentifyingInstance(metadataIdentificationString),
        "Only metadata instances can be cached (not '%s')", metadataIdentificationString);
    map.remove(metadataIdentificationString);
  }

  public void evictAll() {
    init();
  }

  protected int getCacheSize() {
    return map.size();
  }

  protected MetadataItem getFromCache(final String metadataIdentificationString) {
    Validate.isTrue(
        MetadataIdentificationUtils.isIdentifyingInstance(metadataIdentificationString),
        "Only metadata instances can be cached (not '%s')", metadataIdentificationString);
    return map.get(metadataIdentificationString);
  }

  public int getMaxCapacity() {
    return maxCapacity;
  }

  private void init() {
    final int hashTableCapacity = (int) Math.ceil(maxCapacity / hashTableLoadFactor) + 1;
    map = new LinkedHashMap<String, MetadataItem>(hashTableCapacity, hashTableLoadFactor, true) {
      private static final long serialVersionUID = 1;

      @Override
      protected boolean removeEldestEntry(final Map.Entry<String, MetadataItem> eldest) {
        return size() > maxCapacity;
      }
    };
  }

  public void put(final MetadataItem metadataItem) {
    Validate.notNull(metadataItem, "A metadata item is required");
    map.put(metadataItem.getId(), metadataItem);
  }

  public void setMaxCapacity(int maxCapacity) {
    if (maxCapacity < 100) {
      maxCapacity = 100;
    }
    this.maxCapacity = maxCapacity;
    init();
  }
}