Package freemarker.cache

Class MruCacheStorage

java.lang.Object
freemarker.cache.MruCacheStorage
All Implemented Interfaces:
CacheStorage, CacheStorageWithGetSize
public class MruCacheStorage extends Object implements CacheStorageWithGetSize
A cache storage that implements a two-level Most Recently Used cache. In the first level, items are strongly referenced up to the specified maximum. When the maximum is exceeded, the least recently used item is moved into the second level cache, where they are softly referenced, up to another specified maximum. When the second level maximum is also exceeded, the least recently used item is discarded altogether. This cache storage is a generalization of both StrongCacheStorage and SoftCacheStorage - the effect of both of them can be achieved by setting one maximum to zero and the other to the largest positive integer. On the other hand, if you wish to use this storage in a strong-only mode, or in a soft-only mode, you might consider using StrongCacheStorage or SoftCacheStorage instead, as they can be used by TemplateCache concurrently without any synchronization on a 5.0 or later JRE.

This class is NOT thread-safe. If it's accessed from multiple threads concurrently, proper synchronization must be provided by the callers. Note that TemplateCache, the natural user of this class provides the necessary synchronizations when it uses the class. Also you might consider whether you need this sort of a mixed storage at all in your solution, as in most cases SoftCacheStorage can also be sufficient. SoftCacheStorage will use Java soft references, and they already use access timestamps internally to bias the garbage collector against clearing recently used references, so you can get reasonably good (and memory-sensitive) most-recently-used caching through SoftCacheStorage as well.

See Also:
Configuration.setCacheStorage(CacheStorage)

  • Constructor Details

    • MruCacheStorage

      public MruCacheStorage​(int strongSizeLimit, int softSizeLimit)
      Creates a new MRU cache storage with specified maximum cache sizes. Each cache size can vary between 0 and Integer.MAX_VALUE.
      Parameters:
      strongSizeLimit - the maximum number of strongly referenced templates; when exceeded, the entry used the least recently will be moved into the soft cache.
      softSizeLimit - the maximum number of softly referenced templates; when exceeded, the entry used the least recently will be discarded.

  • Method Details

    • get

      public Object get​(Object key)
      Specified by:
      get in interface CacheStorage

    • put

      public void put​(Object key, Object value)
      Specified by:
      put in interface CacheStorage

    • remove

      public void remove​(Object key)
      Specified by:
      remove in interface CacheStorage

    • clear

      public void clear()
      Specified by:
      clear in interface CacheStorage

    • getStrongSizeLimit

      public int getStrongSizeLimit()
      Returns the configured upper limit of the number of strong cache entries.
      Since:
      2.3.21

    • getSoftSizeLimit

      public int getSoftSizeLimit()
      Returns the configured upper limit of the number of soft cache entries.
      Since:
      2.3.21

    • getStrongSize

      public int getStrongSize()
      Returns the current number of strong cache entries.
      Since:
      2.3.21
      See Also:
      getStrongSizeLimit()

    • getSoftSize

      public int getSoftSize()
      Returns a close approximation of the current number of soft cache entries.
      Since:
      2.3.21
      See Also:
      getSoftSizeLimit()

    • getSize

      public int getSize()
      Returns a close approximation of the current number of cache entries.
      Specified by:
      getSize in interface CacheStorageWithGetSize
      Since:
      2.3.21
      See Also:
      getStrongSize(), getSoftSize()