CacheKey.java |
/* * JBoss, the OpenSource J2EE webOS * * Distributable under LGPL license. * See terms of license at gnu.org. */ package org.jboss.ejb; import java.io.Externalizable; import java.io.ObjectOutput; import java.io.ObjectInput; import java.io.IOException; import java.lang.reflect.Method; import java.rmi.MarshalledObject; import org.jboss.logging.Logger; /** * CacheKey is an encapsulation of both the PrimaryKey and a * cache specific key. * * <p>This implementation is a safe implementation in the sense that it * doesn't rely on the user supplied hashcode and equals. It is also * fast since the hashCode operation is pre-calculated. * * @see org.jboss.ejb.plugins.NoPassivationInstanceCache.java * @see org.jboss.ejb.plugins.EntityInstanceCache * @see org.jboss.ejb.plugins.EntityProxy * * @author <a href="mailto:marc.fleury@telkel.com">Marc Fleury</a> * @author <a href="bill@burkecentral.com">Bill Burke</a> * @author <a href="Scott.Stark@jboss.org">Scott Stark</a> * @version $Revision: 1.23 $ */ public class CacheKey implements Externalizable { // Constants ----------------------------------------------------- static final long serialVersionUID = -7108821554259950778L; // Attributes ---------------------------------------------------- /** * The database primaryKey. * * This primaryKey is used by: * * org.jboss.ejb.plugins.EntityInstanceCache.setKey() - to set the EntityEnterpriseContext id * org.jboss.ejb.plugins.jrmp.interfaces.EntityProxy.invoke(): * - implementing Entity.toString() --> cacheKey.getId().toString() * - implementing Entity.hashCode() --> cacheKey.getId().hashCode() * - etc... * org.jboss.ejb.plugins.local.BaseLocalProxyFactory.EntityProxy.getId() */ protected Object id; public Object getId() { return id; } /** The Marshalled Object representing the key */ protected MarshalledObject mo; /** The Marshalled Object's hashcode */ protected int hashCode; // Static -------------------------------------------------------- // Public -------------------------------------------------------- public CacheKey() { // For externalization only } public CacheKey(Object id) { // why does this throw an error and not an IllegalArgumentException ? if (id == null) throw new Error("id may not be null"); this.id = id; try { /* See if the key directly implements equals and hashCode. The *getDeclaredMethod method only returns method declared in the argument *class, not its superclasses. */ try { Class[] equalsArgs = {Object.class}; Method equals = id.getClass().getDeclaredMethod("equals", equalsArgs); Class[] hashCodeArgs = {}; Method hash = id.getClass().getDeclaredMethod("hashCode", hashCodeArgs); // Both equals and hashCode are defined, use the id methods hashCode = id.hashCode(); } catch(NoSuchMethodException ex) { // Rely on the MarshalledObject for equals and hashCode mo = new MarshalledObject(id); // Precompute the hashCode (speed) hashCode = mo.hashCode(); } } catch (Exception e) { Logger log = Logger.getLogger(getClass()); log.error("failed to initialize, id="+id, e); } } // Z implementation ---------------------------------------------- // Package protected --------------------------------------------- // Protected ----------------------------------------------------- // Private ------------------------------------------------------- public void writeExternal(ObjectOutput out) throws IOException { out.writeObject(id); out.writeObject(mo); out.writeInt(hashCode); } public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException { id = in.readObject(); mo = (MarshalledObject) in.readObject(); hashCode = in.readInt(); } // HashCode and Equals over write -------------------------------- /** * these should be overwritten by extending Cache key * since they define what the cache does in the first place */ public int hashCode() { // we default to the pK id return hashCode; } /** This method uses the id implementation of equals if the mo is *null since this indicates that the id class did implement equals. *If mo is not null, then the MarshalledObject equals is used to *compare keys based on their serialized form. Relying on the *serialized form does not always work. */ public boolean equals(Object object) { boolean equals = false; if (object instanceof CacheKey) { CacheKey ckey = (CacheKey) object; Object key = ckey.id; // If mo is null, the id class implements equals if( mo == null ) equals = id.equals(key); else equals = mo.equals(ckey.mo); } return equals; } public String toString() { return id.toString(); } // Inner classes ------------------------------------------------- }
CacheKey.java |