first commit

hrmsEjb/net/sf/jasperreports/engine/util/JRSingletonCache.java

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+package net.sf.jasperreports.engine.util;
+
+import java.util.Map;
+import net.sf.jasperreports.engine.JRException;
+import org.apache.commons.collections.ReferenceMap;
+
+public class JRSingletonCache {
+  private static final Object CONTEXT_KEY_NULL = new Object();
+  
+  private final ReferenceMap cache;
+  
+  private final Class itf;
+  
+  public JRSingletonCache(Class itf) {
+    this.cache = new ReferenceMap(2, 1);
+    this.itf = itf;
+  }
+  
+  public synchronized Object getCachedInstance(String className) throws JRException {
+    Map contextCache = getContextInstanceCache();
+    Object instance = contextCache.get(className);
+    if (instance == null) {
+      instance = createInstance(className);
+      contextCache.put(className, instance);
+    } 
+    return instance;
+  }
+  
+  protected Object createInstance(String className) throws JRException {
+    try {
+      Class clazz = JRClassLoader.loadClassForName(className);
+      if (this.itf != null && !this.itf.isAssignableFrom(clazz))
+        throw new JRException("Class \"" + className + "\" should be compatible with \"" + this.itf.getName() + "\""); 
+      return clazz.newInstance();
+    } catch (ClassNotFoundException e) {
+      throw new JRException("Class " + className + " not found.", e);
+    } catch (InstantiationException e) {
+      throw new JRException("Error instantiating class " + className + ".", e);
+    } catch (IllegalAccessException e) {
+      throw new JRException("Error instantiating class " + className + ".", e);
+    } 
+  }
+  
+  protected Map getContextInstanceCache() {
+    ReferenceMap referenceMap;
+    Object contextKey = getContextKey();
+    Map contextCache = (Map)this.cache.get(contextKey);
+    if (contextCache == null) {
+      referenceMap = new ReferenceMap();
+      this.cache.put(contextKey, referenceMap);
+    } 
+    return (Map)referenceMap;
+  }
+  
+  protected Object getContextKey() {
+    Object key = Thread.currentThread().getContextClassLoader();
+    if (key == null)
+      key = CONTEXT_KEY_NULL; 
+    return key;
+  }
+}