1 /*

     2  * Copyright (c) 2007-2008 Nokia Corporation and/or its subsidiary(-ies).

     3  * All rights reserved.

     4  * This component and the accompanying materials are made available

     5  * under the terms of the License "Eclipse Public License v1.0"

     6  * which accompanies this distribution, and is available

     7  * at the URL "http://www.eclipse.org/legal/epl-v10.html".

     8  *

     9  * Initial Contributors:

    10  * Nokia Corporation - initial contribution.

    11  *

    12  * Contributors:

    13  *

    14  * Description:  

    15  *

    16  */

    17 package com.nokia.helium.metadata.fmpp;

    18 

    19 import java.util.List;

    20 

    21 import javax.persistence.EntityManager;

    22 import javax.persistence.Query;

    23 

    24 import org.apache.log4j.Logger;

    25 

    26 import freemarker.template.SimpleNumber;

    27 import freemarker.template.SimpleScalar;

    28 import freemarker.template.TemplateModel;

    29 import freemarker.template.TemplateSequenceModel;

    30 

    31 class ORMSequenceModel implements TemplateSequenceModel {

    32     public static final int PAGE_SIZE = 750;

    33     private static Logger log = Logger.getLogger(ORMSequenceModel.class);

    34     private Query query;

    35     private int currentPage;

    36     private List<Object> data;

    37     private int size;

    38     private EntityManager entityManager;

    39     private String queryString;    

    40 

    41     @SuppressWarnings("unchecked")

    42     public ORMSequenceModel(EntityManager entityManager, String queryString) {

    43         log.debug("ORMSequenceModel: " + queryString);

    44         this.queryString = queryString;

    45         this.entityManager = entityManager;

    46         // Caching the full size

    47         int page = 0;

    48         do {

    49             query = entityManager.createQuery(queryString);

    50             query.setFirstResult(PAGE_SIZE * page);

    51             query.setMaxResults(PAGE_SIZE);

    52             data = query.getResultList();

    53             // incrementing the size and page.

    54             size += data.size();

    55             page++;

    56         } while (data.size() == PAGE_SIZE);

    57 

    58         // First query

    59         currentPage = 0;

    60         query = entityManager.createQuery(queryString);

    61         query.setFirstResult(currentPage);

    62         query.setMaxResults(PAGE_SIZE);

    63         data = query.getResultList();

    64     }

    65     

    66     /**

    67      * {@inheritDoc}

    68      */

    69     public int size() {

    70         return size;

    71     }

    72 

    73     /**

    74      * {@inheritDoc}

    75      */

    76     @SuppressWarnings("unchecked")

    77     public synchronized TemplateModel get(int index) {

    78         // Calculating the requested page

    79         int page = index / PAGE_SIZE;

    80         // Shall we load a new page

    81         if (page != currentPage) {

    82             query = entityManager.createQuery(queryString);

    83             query.setFirstResult(page * PAGE_SIZE);

    84             query.setMaxResults(PAGE_SIZE);

    85             data = query.getResultList();

    86             currentPage = page;

    87             if (data.size() == 0) {

    88                 return null;

    89             }

    90         }

    91         // Are we out of bound.

    92         if (data.size() <= index % PAGE_SIZE) {

    93             return null;

    94         }

    95         // Let's get the object.

    96         Object obj = data.get(index % PAGE_SIZE);

    97         if (obj instanceof String) {

    98             return new SimpleScalar((String)obj);

    99         } else if (obj instanceof Number) {

   100             return new SimpleNumber((Number)obj);

   101         } else if (obj == null) {

   102             return null;

   103         } else {

   104             return new ORMObjectModel(obj);

   105         }

   106     }

   107     

   108 }