package org.apache.ojb.broker.accesslayer.sql;
   
   /* 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.ref.WeakReference;
  
  import org.apache.ojb.broker.OJBRuntimeException;
  import org.apache.ojb.broker.PersistenceBrokerException;
  import org.apache.ojb.broker.metadata.ClassDescriptor;
  import org.apache.ojb.broker.metadata.FieldDescriptor;
  import org.apache.ojb.broker.util.logging.Logger;
  
  /**
   * Model simple Statements based on ClassDescriptor and/or PrimaryKey
   *
   * @author <a href="mailto:jbraeuchi@hotmail.com">Jakob Braeuchi</a>
   * @version $Id: SqlPkStatement.java,v 1.1 2007-08-24 22:17:39 ewestfal Exp $
   */
  public abstract class SqlPkStatement implements SqlStatement
  {
      // arminw: Use weak reference to allow GC of removed metadata instances
      private WeakReference m_classDescriptor;
      private Logger m_logger;
  
      /** Constructor for SqlPkStatement. */
      public SqlPkStatement(ClassDescriptor aCld, Logger aLogger)
      {
          super();
          m_classDescriptor = new WeakReference(aCld);
          m_logger = aLogger;
      }
  
      /** append table name */
      protected void appendTable(ClassDescriptor cld, StringBuffer stmt)
      {
          stmt.append(cld.getFullTableName());
      }
  
      /**
       * Returns the logger.
       *
       * @return Logger
       */
      protected Logger getLogger()
      {
          return m_logger;
      }
  
      /**
       * Returns the classDescriptor.
       *
       * @return ClassDescriptor
       */
      protected ClassDescriptor getClassDescriptor()
      {
          ClassDescriptor cld = (ClassDescriptor) m_classDescriptor.get();
          if(cld == null)
          {
              throw new OJBRuntimeException("Requested ClassDescriptor instance was already GC by JVM");
          }
          return cld;
      }
  
      /**
       * Generate a sql where-clause for the array of fields
       *
       * @param fields array containing all columns used in WHERE clause
       */
      protected void appendWhereClause(FieldDescriptor[] fields, StringBuffer stmt) throws PersistenceBrokerException
      {
          stmt.append(" WHERE ");
  
          for(int i = 0; i < fields.length; i++)
          {
              FieldDescriptor fmd = fields[i];
  
              stmt.append(fmd.getColumnName());
              stmt.append(" = ? ");
              if(i < fields.length - 1)
              {
                  stmt.append(" AND ");
              }
          }
      }
  
      /**
      * Generate a where clause for a prepared Statement.
      * Only primary key and locking fields are used in this where clause
      *
      * @param cld the ClassDescriptor
      * @param useLocking true if locking fields should be included
      * @param stmt the StatementBuffer
      */
     protected void appendWhereClause(ClassDescriptor cld, boolean useLocking, StringBuffer stmt)
     {
         FieldDescriptor[] pkFields = cld.getPkFields();
         FieldDescriptor[] fields;
 
         fields = pkFields;
         if(useLocking)
         {
             FieldDescriptor[] lockingFields = cld.getLockingFields();
             if(lockingFields.length > 0)
             {
                 fields = new FieldDescriptor[pkFields.length + lockingFields.length];
                 System.arraycopy(pkFields, 0, fields, 0, pkFields.length);
                 System.arraycopy(lockingFields, 0, fields, pkFields.length, lockingFields.length);
             }
         }
 
         appendWhereClause(fields, stmt);
     }
 
 }