db-ojb-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From t...@apache.org
Subject cvs commit: db-ojb/src/java/org/apache/ojb/broker/metadata/fieldaccess PersistentFieldAutoProxyImpl.java
Date Tue, 08 Jul 2003 06:05:00 GMT
thma        2003/07/07 23:05:00

  Added:       src/java/org/apache/ojb/broker/metadata/fieldaccess
                        PersistentFieldAutoProxyImpl.java
  Log:
  add a fieldaccess strategy that can switch automatically to use different other strategies
if needed
  
  Revision  Changes    Path
  1.1                  db-ojb/src/java/org/apache/ojb/broker/metadata/fieldaccess/PersistentFieldAutoProxyImpl.java
  
  Index: PersistentFieldAutoProxyImpl.java
  ===================================================================
  package org.apache.ojb.broker.metadata.fieldaccess;
  
  /* ====================================================================
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution,
   *    if any, must include the following acknowledgment:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgment may appear in the software itself,
   *    if and wherever such third-party acknowledgments normally appear.
   *
   * 4. The names "Apache" and "Apache Software Foundation" and
   *    "Apache ObjectRelationalBridge" must not be used to endorse or promote products
   *    derived from this software without prior written permission. For
   *    written permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache",
   *    "Apache ObjectRelationalBridge", nor may "Apache" appear in their name, without
   *    prior written permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   */
  
  import java.beans.BeanInfo;
  import java.beans.Introspector;
  import java.lang.reflect.Field;
  import java.util.Map;
  
  import org.apache.commons.collections.FastHashMap;
  import org.apache.ojb.broker.metadata.MetadataException;
  import org.apache.ojb.broker.util.ClassHelper;
  import org.apache.ojb.broker.util.logging.LoggerFactory;
  
  /**
   * PeristentField implementation that attempts to detect the nature of
   * the field it is persisting. 
   * <p>
   * First checks to see if it is a Field, then Property, then DynaBean
   * <p>
   * It will match in that order.
   * 
   * @author <a href="brian@frums.net">Brian McCallister</a>
   * @version 
   */
  public class PersistentFieldAutoProxyImpl implements PersistentField
  {
      private PersistentField wrapped;
  
      private static final Class PERSIST_FIELD = PersistentFieldDefaultImpl.class;
      private static final Class PERSIST_PROPERTY = PersistentFieldPropertyImpl.class;
      private static final Class PERSIST_DYNA = PersistentFieldDynaBeanImpl.class;
  
      /**
       * Contains additional maps with name to PersistentFactory implementation Class
       * instances
       */
      private static Map classToName = new FastHashMap();
  
      /**
       * Being nice to Class.newInstance() seems popular.
       */
      public PersistentFieldAutoProxyImpl()
      {
      }
  
      /**
       * Constructor will examine the Class type to attempt to determine what
       * type of attribute this is (field, property, or DynaProperty and 
       * wrap an instance of the correct PersistentField implementation
       * for that field. 
       * <p>
       * TODO: Improve error reporting. Really need to keep why
       * 		 each one failed and give it lump some to the 
       * 		 user so that the user can figure out why the one
       * 		 which was supposed to work didn't
       */
      public PersistentFieldAutoProxyImpl(Class type, String name)
      {
          if (this.tryLoadFromCache(type, name))
          {
              return;
          }
  
          /* 
           * this switches on a series of exceptions. Sadly, it is the only real way to detect

           * which one works. The cache should manage things so this chain only need be called
           * once per field. --Brian
           */
  
          try
          {
              this.tryFieldImpl(type, name);
              return;
          }
          catch (Exception e)
          { // we don't care yet
          }
  
          try
          {
              this.tryPropertyImpl(type, name);
              return;
          }
          catch (Exception e1)
          { // We still don't care
          }
  
          // Only option left is for it to be a dynabean
          try
          {
              this.tryDynaBeanImpl(type, name);
              return;
          }
          catch (Exception e)
          { // Technically we care, but we are baout to throw an exception anyway
          }
  
          // We couldn't match anything, throw Exception
          String message =
              "No field, property, or DynaProperty can be found to match " + type.getName()
+ "." + name + "()";
          LoggerFactory.getDefaultLogger().warn(message);
          throw new MetadataException(message);
      }
  
      private void tryDynaBeanImpl(Class type, String name) throws Exception
      {
          Class[] types = { Class.class, String.class };
          Object[] args = { type, name };
  
          wrapped = (PersistentField) ClassHelper.newInstance(PERSIST_DYNA, types, args);
  
      }
  
      private void tryPropertyImpl(Class type, String name) throws Exception
      {
          BeanInfo info = Introspector.getBeanInfo(type);
          Class[] types = { Class.class, String.class };
          Object[] args = { type, name };
  
          wrapped = (PersistentField) ClassHelper.newInstance(PERSIST_PROPERTY, types, args);
      }
  
      /**
       * If it finds an implementation in the cache it will load it into the
       * wrapped field and return true.
       */
      private boolean tryLoadFromCache(Class type, String name)
      {
          if (classToName.containsKey(name))
          {
              Map nameToImpl = (Map) classToName.get(name);
              if (nameToImpl.containsKey(name))
              {
                  Class[] types = { Class.class, String.class };
                  Object[] args = { type, name };
                  Class clazz = (Class) nameToImpl.get(type);
                  try
                  {
                      wrapped = (PersistentField) ClassHelper.newInstance(clazz, types, args);
                  }
                  catch (Exception e2)
                  {
                      LoggerFactory.getLogger(this.getClass()).warn(
                          "Unable to use cached PersistentField: " + clazz.getName(),
                          e2);
                      throw new MetadataException("Unable to use cached PersistentField: ",
e2);
                  }
                  return true;
              }
          }
          return false;
      }
  
      private void tryFieldImpl(Class type, String name) throws Exception
      {
          Field field = this.getFieldRecursive(type, name);
          Class[] types = { Class.class, String.class };
          Object[] args = { type, name };
  
          wrapped = (PersistentField) ClassHelper.newInstance(PERSIST_FIELD, types, args);
  
      }
  
      /**
       * REFACTOR: This is cut and paste code from PersistentFieldDefaultImpl, 
       *
       * @throws NoSuchFieldException if no Field was found into the class hierarchy
       */
      protected Field getFieldRecursive(Class c, String name) throws NoSuchFieldException
      {
          try
          {
              Field f = c.getDeclaredField(name);
              return f;
          }
          catch (NoSuchFieldException e)
          {
              // if field  could not be found in the inheritance hierarchy, signal error
              if (c == Object.class)
              {
                  throw e;
              }
              // if field could not be found in class c try in superclass
              else
              {
                  return getFieldRecursive(c.getSuperclass(), name);
              }
          }
      }
  
      private static synchronized void addToCache(Class type, String name, Class pfClass)
      {
          Map nameToImpl = null;
          if (classToName.containsKey(type))
          {
              nameToImpl = (Map) classToName.get(type);
          }
          else
          {
              nameToImpl = new FastHashMap();
          }
          nameToImpl.put(name, pfClass);
      }
  
      /* These are all the implementation methods delagating to the wrapped impl*/
  
      public Class getDeclaringClass()
      {
          return wrapped.getDeclaringClass();
      }
  
      public void set(Object obj, Object value) throws MetadataException
      {
          wrapped.set(obj, value);
      }
  
      public Object get(Object anObject) throws MetadataException
      {
          return wrapped.get(anObject);
      }
  
      public boolean usesAccessorsAndMutators()
      {
          return wrapped.usesAccessorsAndMutators();
      }
  
      public String getName()
      {
          return wrapped.getName();
      }
  
      public Class getType()
      {
          return wrapped.getType();
      }
  
  }
  
  
  

---------------------------------------------------------------------
To unsubscribe, e-mail: ojb-dev-unsubscribe@db.apache.org
For additional commands, e-mail: ojb-dev-help@db.apache.org


Mime
View raw message