Ehcache Example - Namespace - Raster, Medical, Document Help

Ehcache Example

Below is a cache example that uses the popular Java Ehcache system.

First, generate or obtain an Ehcache manager configuration file. This is an example that creates a cache with off heap options and has the alias leadtools:

Content of ehcache.xml

XML
<config 
    xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' 
    xmlns='http://www.ehcache.org/v3' 
    xsi:schemaLocation="http://www.ehcache.org/v3 http://www.ehcache.org/schema/ehcache-core.xsd"> 
 
  <cache alias="leadtools">  
    <key-type>java.lang.String</key-type> 
    <value-type>java.io.Serializable</value-type> 
    <resources> 
      <heap unit="MB">100</heap> 
      <offheap unit="GB">1</offheap> 
    </resources> 
  </cache> 
</config> 

Next, add the following LEADTOOLS cache configuration XML file to the Document service. This XML file references the class implementing ehCache described below, the cache manager file and alias:

Content of lead-ehcache.xml

XML
<?xml version="1.0" encoding="utf-8"?> 
<leadtools_cache> 
  <cache> 
    <type>com.yourapp.EhcacheObjectCache</type> 
    <values> 
      <value key="manager-config-file" value="ehcache.xml" /> 
      <value key="cache-alias" value="leadtools" /> <!-- must be defined in above cache manager config file --> 
    </values> 
  </cache> 
</leadtools_cache> 

Replace the code inside ServiceHelper.CreateCache with initialization of the Ehcache object as shown in the example:

Java
// The path to lead_ehcache_config.xml 
String config = "lead_ehcache_config.xml"; 
try (FileInputStream fis = new FileInputStream(config)) { 
    try (LeadDynamicStream lds = new LeadDynamicStream(fis, true)) { 
        // Create it 
        ObjectCache cache = ObjectCache.createFromConfigurations(lds, null); 
        // Use it 
        ServiceHelper._cache = cache; 
    } 
} 

Finally, this is implementation of EhcacheObjectCache:

Java
package com.yourapp; 
 
import java.io.ByteArrayInputStream; 
import java.io.ByteArrayOutputStream; 
import java.io.File; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.io.Serializable; 
import java.net.MalformedURLException; 
import java.net.URI; 
import java.net.URL; 
import java.util.EnumSet; 
import java.util.HashSet; 
import java.util.Iterator; 
import java.util.Map; 
import java.util.Set; 
 
import org.ehcache.Cache; 
import org.ehcache.CacheManager; 
import org.ehcache.config.builders.CacheManagerBuilder; 
import org.ehcache.xml.XmlConfiguration; 
 
import leadtools.InvalidOperationException; 
import leadtools.RasterException; 
import leadtools.caching.CacheItem; 
import leadtools.caching.CacheItemExpiredEvent; 
import leadtools.caching.CacheItemExpiringEvent; 
import leadtools.caching.CacheItemPolicy; 
import leadtools.caching.CacheSerializationMode; 
import leadtools.caching.CacheStatistics; 
import leadtools.caching.DefaultCacheCapabilities; 
import leadtools.caching.EnumerateCacheEntriesCallback; 
import leadtools.caching.ObjectCache; 
 
/* 
Implementation of leadtools.caching.ObjectCache that wraps an org.ehcache.Cache object 
 
1. Create or load an instance Cache. 
2. Create an instance of EhcacheObjectCache to wrap it 
3. Pass it to LEADTOOLS Documents toolkit that expect a CacheObject. For instance, DocumentFactory.loadFromUrl or DocumentFactory.loadFromCache. Then everything 
should work as expected 
4. To delete a document from the cache, use DocumentFactory.deleteFromCache 
 
This implementation does not support individual expiration policies for each item since this is not supported by Ehcache. Instead, it will use the policies 
already setup in the original Ehcache object passed. 
 
The document toolkit will call the following methods of ObjectCache: 
 
- getDefaultCacheCapabilities to get the kind of support of this cache. We support minimal requirement of get/set only (no regions, external URLs, disk 
access nor auto-serialization). 
 
- addOrGetExisting: To add items to the cache using the following parameters: 
 
item.regionName: Will always be the document ID (leadtools.documents.Document.getDocumentId) 
item.keyName: Unique identified for this item, such as page1_image or document_metadata. 
The implementation uses regionName + "_" + keyName to create a unique identifier in the cache since true grouping is not supported by Ehcache. 
item.Value: The value to store, this could be: 
-  Array of bytes: In case of original document data and annotation data 
-  Strings: In case of raster codecs options, meta data, etc. 
-  RasterImage and ISvgDocument objects: If DocumentCacheOptions.PAGE_IMAGE, PAGE_SVG, PAGE_SVG_BACK_IMAGE or PAGE_THUMBNAIL_IMAGE was used to cache images. If 
this occurs, it is recommended that the implementer calls the static tryDispose method from a CacheEventListender when items are removed, evicted, expired or 
updates. Refer to the example code for more information. 
-  getCacheItem: to get items from the cache. Refer to the parameters above. 
-  remove: to remove an item from the cache while returning the original value. 
-  deleteItem: to delete an item from the cache quickly. 
-  deleteAll: to delete multiple items from the cache quickly. This is called when the document is removed from the cache using 
Document.setAutoDeleteFromCache(true) or DocumentFactory.deleteFromCache. 
*/ 
 
public class EhcacheObjectCache extends ObjectCache { 
 
   // Configuration options for this class 
   public static class Configuration { 
      // For future use 
   } 
 
   // The Ehcache object we are wrapping 
   private Cache<String, Serializable> _cache; 
   public Cache<String, Serializable> cache() { 
      return _cache; 
   } 
 
   // No param constructor required for super.createFromConfigurations(ILeadStream) 
   // where this object is instantiated via reflection 
   public EhcacheObjectCache() { 
      super(); 
   } 
 
   public EhcacheObjectCache(Cache<String, Serializable> cache) { 
      super(); 
      if (cache == null) { 
         throw new IllegalArgumentException("cache must not be null"); 
      } 
      init(cache, null, null, null); 
   } 
 
   public EhcacheObjectCache(Cache<String, Serializable> cache, EhcacheObjectCache.Configuration config) { 
      super(); 
      if (cache == null) { 
         throw new IllegalArgumentException("cache must not be null"); 
      } 
      init(cache, null, null, config); 
   } 
    
   public EhcacheObjectCache(String cacheManagerConfigFile, String cacheAlias) { 
      super(); 
      if (cacheManagerConfigFile == null || cacheAlias == null) { 
         throw new IllegalArgumentException("cacheManagerConfigFile and cacheAlias must not be null"); 
      } 
      init(null, cacheManagerConfigFile, cacheAlias, null); 
   } 
    
   public EhcacheObjectCache(String cacheManagerConfigFile, String cacheAlias, EhcacheObjectCache.Configuration config) { 
      super(); 
      if (cacheManagerConfigFile == null || cacheAlias == null) { 
         throw new IllegalArgumentException("cacheManagerConfigFile and cacheAlias must not be null"); 
      } 
      init(null, cacheManagerConfigFile, cacheAlias, config); 
   } 
 
   public void init(Cache<String, Serializable> cache, String managerConfigFile, String cacheAlias, EhcacheObjectCache.Configuration config) { 
       
      if(cache != null) { 
         this._cache = cache; 
      } 
      else { 
         Cache<String, Serializable> createdCache = cacheFromManagerConfig(managerConfigFile, cacheAlias); 
         if(createdCache != null) { 
            init(createdCache, null, null, config); 
            return; 
         } 
      } 
   } 
 
   // Helper method to resolve region and key pair. The document will refer to each item by a region (the document ID, not unique in the cache) and a key 
   // (the value itself, unique for the document ID). Ehcache does not support that, so simply concatenate both values to generate a unique key 
   private static String resolveKey(String key, String region) { 
      if (region == null || region.length() == 0) { 
         // We do not support this 
         throw new UnsupportedOperationException("Cache region must be provided"); 
      } 
 
      return region + "_" + key; 
   } 
 
   // Not used in this implementation 
   @Override 
   public CacheItemExpiringEvent cacheItemExpiring() { 
      return null; 
   } 
 
   // Not used in this implementation 
   @Override 
   public CacheItemExpiredEvent cacheItemExpired() { 
      return null; 
   } 
 
   @Override 
   public String getName() { 
      return "Ehcache ObjectCache"; 
   } 
 
   // We only support binary serialization 
 
   @Override 
   public CacheSerializationMode getPolicySerializationMode() { 
      return CacheSerializationMode.BINARY; 
   } 
 
   @Override 
   public void setPolicySerializationMode(CacheSerializationMode value) { 
      // This is never called from the document toolkit 
   } 
 
   @Override 
   public CacheSerializationMode getDataSerializationMode() { 
      return CacheSerializationMode.BINARY; 
   } 
 
   @Override 
   public void setDataSerializationMode(CacheSerializationMode value) { 
      // This is never called from the document toolkit 
   } 
 
   @Override 
   public boolean contains(String key, String regionName) { 
      if (key == null) 
         throw new IllegalArgumentException("Key cannot be null"); 
 
      return _cache.containsKey(resolveKey(key, regionName)); 
   } 
 
   @Override 
   public <T> T get(String key, Class<?> classOfT) { 
      // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public <T> void set(String key, T value, Class<?> classOfT) { 
      // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public void enumerateRegions(EnumerateCacheEntriesCallback callback) { 
   // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public void enumerateKeys(String region, EnumerateCacheEntriesCallback callback) { 
   // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public Map<String, Object> getValues(Iterator<String> keys, String regionName) { 
   // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   private static boolean isAutoSerializable(Class<?> classOfT) { 
      String classOfTName = classOfT.getCanonicalName(); 
      if (classOfTName.equals("java.lang.Long") || 
         classOfTName.equals("java.lang.Integer") || 
         classOfTName.equals("java.lang.Float") || 
         classOfTName.equals("java.lang.Double") || 
         classOfTName.equals("java.lang.Character") || 
         classOfTName.equals("java.lang.String") || 
         classOfTName.equals("byte[]")) 
         return true; 
      else 
         return false; 
   } 
 
   private <T> void putValue(String resolvedKey, T value, Class<?> classOfT) throws IOException { 
      if (!isAutoSerializable(classOfT)) { 
         try (ByteArrayOutputStream bos = new ByteArrayOutputStream()) { 
            try (ObjectOutputStream out = new ObjectOutputStream(bos)) { 
               out.writeObject(value); 
               byte[] data = bos.toByteArray(); 
               _cache.put(resolvedKey, data); 
            } 
         } 
      } else { 
         _cache.put(resolvedKey, (Serializable)value); 
      } 
   } 
 
   @SuppressWarnings("unchecked") 
   private <T> T getValue(String resolvedKey, Class<?> classOfT) throws ClassNotFoundException, IOException { 
      if (!isAutoSerializable(classOfT)) { 
         byte[] data = (byte[])_cache.get(resolvedKey); 
         if (data != null) { 
            try (ByteArrayInputStream bis = new ByteArrayInputStream(data)) { 
               try (ObjectInputStream in = new ObjectInputStream(bis)) { 
                  T value = (T)in.readObject(); 
                  return value; 
               } 
            } 
         } 
      } else { 
         Object value = _cache.get(resolvedKey); 
         if (value != null) { 
            return (T)value; 
         } 
      } 
 
      return null; 
   } 
 
   @Override 
   public <T> CacheItem<T> addOrGetExisting(CacheItem<T> item, Class<?> classOfT, CacheItemPolicy policy) { 
      if (item == null) { 
         throw new IllegalArgumentException("item cannot be null"); 
      } 
       
      // Get the unique key 
      // Get the current item (if exists) 
      // Put the new item 
      // Return the old item 
      // Note: policy is not used 
 
      String resolvedKey = resolveKey(item.getKey(), item.getRegionName()); 
 
      CacheItem<T> oldItem = null; 
      if (_cache.containsKey(resolvedKey)) { 
         try { 
            oldItem = getCacheItem(item.getKey(), classOfT, item.getRegionName()); 
         } catch (Exception ex) { 
            oldItem = null; 
         } 
      } 
       
       
      if(item.getValue() == null) 
         throw new RuntimeException("CacheItem value cannot be null"); 
 
      try { 
         putValue(resolvedKey, item.getValue(), classOfT); 
      } catch (IOException e) { 
         throw RasterException.fromThrowable(e); 
      } 
      return oldItem; 
   } 
 
   @Override 
   public <T> CacheItem<T> getCacheItem(String key, Class<?> classOfT, String regionName) { 
      // Get the unique key 
      // Get the item 
 
      String resolvedKey = resolveKey(key, regionName); 
      T value; 
      try { 
         value = getValue(resolvedKey, classOfT); 
      } catch (ClassNotFoundException | IOException e) { 
         throw RasterException.fromThrowable(e); 
      } 
      if (value != null) { 
         return new CacheItem<T>(key, value, regionName); 
      } 
 
      return null; 
   } 
 
   @Override 
   public <T> T remove(String key, Class<?> classOfT, String regionName) { 
      // Get the unique key 
      // Get the old value 
      // Remove the item 
      // Return the old value 
 
      T value = null; 
      String resolvedKey = resolveKey(key, regionName); 
      if (_cache.containsKey(resolvedKey)) { 
         try { 
            value = getValue(resolvedKey, classOfT); 
         } catch (ClassNotFoundException | IOException e) { 
            throw RasterException.fromThrowable(e); 
         } 
         _cache.remove(resolvedKey); 
      } 
 
      return value; 
   } 
 
   @Override 
   public void deleteItem(String key, String regionName) { 
      // Get the unique key 
      // Remove the item 
 
      String resolvedKey = resolveKey(key, regionName); 
      if (_cache.containsKey(resolvedKey)) { 
         _cache.remove(resolvedKey); 
      } 
   } 
 
   @Override 
   public long getCount(String regionName) { 
      // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public EnumSet<DefaultCacheCapabilities> getDefaultCacheCapabilities() { 
      EnumSet<DefaultCacheCapabilities> caps = EnumSet.of(DefaultCacheCapabilities.NONE); 
      caps.add(DefaultCacheCapabilities.SERIALIZATION); 
      return caps; 
   } 
 
   @Override 
   public URI getItemVirtualDirectoryUrl(String key, String regionName) { 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public CacheStatistics getStatistics(String keyName, String regionName) { 
      // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public CacheStatistics getStatistics() { 
      // This is never called from the document toolkit 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public void deleteRegion(String regionName) { 
      throw new UnsupportedOperationException("Method not supported. Use deleteAll"); 
      // One cache per document implementation. Try to delete _cache from the manage if not needed 
   } 
 
   @Override 
   public URI getItemExternalResource(String key, String regionName, boolean readWrite) { 
      /// This is never called from the document toolkit since we do not support DefaultCacheCapabilities.EXTERNAL_RESOURCES 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public void removeItemExternalResource(String key, String regionName) { 
      /// This is never called from the document toolkit since we do not support DefaultCacheCapabilities.EXTERNAL_RESOURCES 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public URI beginAddExternalResource(String key, String regionName, boolean readWrite) { 
      /// This is never called from the document toolkit since we do not support DefaultCacheCapabilities.EXTERNAL_RESOURCES 
      throw new UnsupportedOperationException(); 
   } 
 
   @Override 
   public <T> void endAddExternalResource(boolean commit, String key, T value, Class<?> classOfT, CacheItemPolicy policy, String regionName) { 
      /// This is never called from the document toolkit since we do not support DefaultCacheCapabilities.EXTERNAL_RESOURCES 
      throw new UnsupportedOperationException(); 
   } 
    
   @Override 
   public void updatePolicy(String key, CacheItemPolicy policy, String regionName) { 
      // Method not supported. Policies are set on the Cache object passed to the constructor. 
      // This will be called from the document toolkit. But we can safely ignore it and rely on the 
      // expiration policies always set up in the Ehcache object from outside. 
   } 
 
   @Override 
   public <T> boolean updateCacheItem(CacheItem<T> item, Class<?> classOfT) { 
      // Get the unique key 
      // If item found, update it 
      // return status 
 
      String resolvedKey = resolveKey(item.getKey(), item.getRegionName()); 
      if (_cache.containsKey(resolvedKey)) { 
         try { 
            putValue(resolvedKey, item.getValue(), classOfT); 
         } catch (IOException e) { 
            throw RasterException.fromThrowable(e); 
         } 
         return true; 
      } else { 
         return false; 
      } 
   } 
 
   @Override 
   public void deleteAll(String regionName, Set<String> keys) { 
      if (keys == null) { 
         return; 
      } 
 
      // Remove all the keys 
      // Note that the document toolkit will call this method with keys for items that may not exist 
      // in the cache, Ehcache does not have a problem with that so just call removeAll instead 
      // of trying to iterate through the keys to check if they exist first. 
 
      // Of course, convert to our key format first 
      Set<String> resolvedKeys = new HashSet<String>(); 
      for (String key: keys) { 
         resolvedKeys.add(resolveKey(key, regionName)); 
      } 
 
      _cache.removeAll(resolvedKeys); 
   } 
    
   private Cache<String, Serializable> cacheFromManagerConfig(String managerConfigFile, String cacheAlias) { 
       
      if (managerConfigFile != null) { 
         URL url = Thread.currentThread().getContextClassLoader().getResource(managerConfigFile); 
         if(url == null) { 
            //Loading resource failed. Try absolute path. 
            File configFile = new File(managerConfigFile); 
            if(configFile.exists()) { 
               try { 
                  url = configFile.toURI().toURL(); 
               } 
               catch(MalformedURLException ex) { 
                  throw new InvalidOperationException("CacheManager config file could not be found"); 
               } 
            } 
         } 
         this.setManagerConfigFile(managerConfigFile); 
         XmlConfiguration xmlConfig = new XmlConfiguration(url); 
         _cacheManager = CacheManagerBuilder.newCacheManager(xmlConfig); 
         _cacheManager.init(); 
         if(cacheAlias != null) { 
            Cache<String, Serializable> cache = _cacheManager.getCache(cacheAlias, String.class, Serializable.class); 
            this.setCacheAlias(cacheAlias); 
            return cache; 
         } 
         else { 
            throw new InvalidOperationException("Ehcache cache alias must not be null"); 
         } 
          
      } 
      else { 
         throw new InvalidOperationException("Ehcache CacheManager config file must not be null"); 
      } 
   } 
    
   @Override 
   protected void loadConfigurationValues(Map<String, String> values) { 
      super.loadConfigurationValues(values); 
 
      String configFile = values.get("manager-config-file"); 
      String cacheAlias = values.get("cache-alias"); 
       
      if(configFile == null || cacheAlias == null) { 
         throw new InvalidOperationException("Ehcache CacheManager config file and Ehcache cache alias must not be null"); 
      } 
       
      EhcacheObjectCache.Configuration cfg = new EhcacheObjectCache.Configuration(); 
       
      Cache<String, Serializable> cache = cacheFromManagerConfig(configFile, cacheAlias); 
      init(cache, null, null, cfg); 
       
   } 
    
   @Override 
   protected void saveConfigurationValues(Map<String, String> values) 
   { 
      super.saveConfigurationValues(values); 
       
      if(this.getManagerConfigFile() != null) { 
         values.put("manager-config-file", this.getManagerConfigFile()); 
      } 
       
      if(this.getCacheAlias() != null) { 
         values.put("cache-alias", this.getCacheAlias()); 
      } 
   } 
    
   private String _configFile; 
   // Can be null if this object is initiated with a Cache reference instead of  
   // a CacheManager configuration file 
   public String getManagerConfigFile() { 
      return _configFile; 
   } 
    
   void setManagerConfigFile(String configFile) { 
      this._configFile = configFile; 
   } 
    
   private CacheManager _cacheManager; 
   // Can be null if this object is initiated with a Cache reference instead of  
   // a CacheManager configuration file 
   public CacheManager getManager() { 
      return _cacheManager; 
   } 
    
   void setManager(CacheManager manager) { 
      this._cacheManager = manager; 
   } 
    
   private String _cacheAlias; 
   // Can be null if this object is initiated with a Cache reference instead of  
   // a CacheManager configuration file 
   public String getCacheAlias() { 
      return this._cacheAlias; 
   } 
    
   void setCacheAlias(String cacheAlias) { 
      this._cacheAlias = cacheAlias; 
   } 
} 

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