package org.apache.ojb.broker.accesslayer;

 /* Copyright 2002-2005 The Apache Software Foundation

  *

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 import java.lang.reflect.Constructor;

 import java.sql.SQLException;

 import java.util.Enumeration;

 import java.util.NoSuchElementException;

 import org.apache.ojb.broker.Identity;

 import org.apache.ojb.broker.PersistenceBroker;

 import org.apache.ojb.broker.PersistenceBrokerException;

 import org.apache.ojb.broker.PersistenceBrokerSQLException;

 import org.apache.ojb.broker.metadata.ClassDescriptor;

 import org.apache.ojb.broker.metadata.FieldDescriptor;

 import org.apache.ojb.broker.query.Query;

 import org.apache.ojb.broker.util.ConstructorHelper;

 import org.apache.ojb.broker.util.logging.LoggerFactory;

 /**

  * this class can be used to create enumerations of PrimaryKey objects.

  * This is interesting for EJB finder methods

  * in BMP entity beans which must return such enumerations.

  * @author Thomas Mahler

  * @version $Id: PkEnumeration.java,v 1.1 2007-08-24 22:17:30 ewestfal Exp $

  */

 public class PkEnumeration implements Enumeration

 {

         static final long serialVersionUID = -834955711995869884L;

     protected boolean hasCalledCheck = false;

     protected boolean hasNext = false;

     protected PersistenceBroker broker;

     /**

      * The underlying jdbc resultset produced by select statement

      */

     protected ResultSetAndStatement resultSetAndStatment;

     /**

      * descriptor for the class of which items are to be found

      */

     protected ClassDescriptor classDescriptor;

     /**

      * the Constructor that is needed to build the PrimaryKey Objects

      */

     protected Constructor constructor;

     /**

      * PkEnumeration constructor.

      * @param query the SELECT statement gerating the underlying resultset

      * @param cld classDescriptor of the target entity class (say Article)

      * @param primaryKeyClass the entity classes PrimaryKey class (say ArticleKey).

      * this key-class MUST have a constructor with one argument of type org.apache.ojb.broker.Identity !

      */

     public PkEnumeration(Query query, ClassDescriptor cld, Class primaryKeyClass, PersistenceBroker broker)

     {

         this.resultSetAndStatment = broker.serviceJdbcAccess().executeQuery(query, cld);

         this.classDescriptor = cld;

         this.broker = broker;

         // get a contructor object that can be used to build instances of class primaryKeyClass

         try

         {

             Class[] argArray = {Identity.class};

             this.constructor = primaryKeyClass.getConstructor(argArray);

         }

         catch (NoSuchMethodException e)

         {

             LoggerFactory.getDefaultLogger().error(primaryKeyClass.getName()

                     + " must implement a Constructor with one argument of type org.apache.ojb.broker.Identity");

             throw new PersistenceBrokerException(e);

         }

         catch (SecurityException e)

         {

             LoggerFactory.getDefaultLogger().error(e);

             throw new PersistenceBrokerException(e);

         }

     }

     /**

      * returns an Identity object representing the current resultset row

      */

     private Identity getIdentityFromResultSet()

     {

         try

         {

             // 1. get an empty instance of the target class

             Constructor con = classDescriptor.getZeroArgumentConstructor();

             Object obj = ConstructorHelper.instantiate(con);

             // 2. fill only primary key values from Resultset

             Object colValue;

             FieldDescriptor fld;

             FieldDescriptor[] pkfields = classDescriptor.getPkFields();

             for (int i = 0; i < pkfields.length; i++)

             {

                 fld = pkfields[i];

                 colValue = fld.getJdbcType().getObjectFromColumn(resultSetAndStatment.m_rs, fld.getColumnName());

                 fld.getPersistentField().set(obj, colValue);

             }

             // 3. return the representing identity object

             return broker.serviceIdentity().buildIdentity(classDescriptor, obj);

         }

         catch (SQLException e)

         {

             throw new PersistenceBrokerSQLException("Error reading object from column", e);

         }

         catch (Exception e)

         {

             throw new PersistenceBrokerException("Error reading Identity from result set", e);

         }

     }

     /**

      * Tests if this enumeration contains more elements.

      * @return  <code>true</code> if and only if this enumeration object

      * contains at least one more element to provide;

      * <code>false</code> otherwise.

      */

     public boolean hasMoreElements()

     {

         try

         {

             if (!hasCalledCheck)

             {

                 hasCalledCheck = true;

                 hasNext = resultSetAndStatment.m_rs.next();

             }

         }

         catch (SQLException e)

         {

             LoggerFactory.getDefaultLogger().error(e);

             //releaseDbResources();

             hasNext = false;

         }

         finally

         {

             if(!hasNext)

             {

                 releaseDbResources();

             }

         }

         return hasNext;

     }

     private void releaseDbResources()

     {

         resultSetAndStatment.close();

         resultSetAndStatment = null;

     }

     /**

      * Returns the next element of this enumeration if this enumeration

      * object has at least one more element to provide.

      * @return     the next element of this enumeration.

      * @exception  NoSuchElementException  if no more elements exist.

      */

     public Object nextElement()

     {

         try

         {

             if (!hasCalledCheck)

             {    

                 hasMoreElements();

             }    

             hasCalledCheck = false;

             if (hasNext)

             {

                 Identity oid = getIdentityFromResultSet();

                 Identity[] args = {oid};

                 return this.constructor.newInstance(args);

             }

             else

                 throw new NoSuchElementException();

         }

         catch (Exception ex)

         {

             LoggerFactory.getDefaultLogger().error(ex);

             throw new NoSuchElementException();

         }

     }

         /**

          * protection just in case someone leaks.

          */

         protected void finalize()

         {

                 if(resultSetAndStatment != null)

         {

             LoggerFactory.getDefaultLogger().error("["+PkEnumeration.class.getName()+"] Found unclosed resources while finalize");

             releaseDbResources();

         }

         }

 }