Optimizations for the models processing content items.

ccm-cms-default-theme/src/main/resources/themes/librecms/templates/index-page.html.ftl

@@ -4,21 +4,33 @@
     <div class="container">
         <div class="bg-light mb-4 rounded-3">
             <div class="container-fluid py-5">
-                <h1 class="display-5 fw-bold">
+                <#if CmsPagesCategorizedItemModel.itemAvailable>
-                    LibreCMS 
+                    <h1 class="display-5 fw-bold">
-                </h1>
+                        ${CmsPagesCategorizedItemModel.title}
-                <p>
+                    </h1>
-                    No index item has been defined.
+                    <p>
-                </p>
+                        ${CmsPagesCategorizedItemModel.description}
-                <a class="btn btn-primary btn-lg"
+                    </p>
-                   href="https://www.libreccm.org"
+                    <a class="btn btn-primary btn-lg"
-                   type="button">
+                       href="#">
-                    Find out more
+                        Find out more
-                </a>
+                    </a>
+                <#else>
+                    <h1 class="display-5 fw-bold">
+                        LibreCMS 
+                    </h1>
+                    <p>
+                        No index item has been defined.
+                    </p>
+                    <a class="btn btn-primary btn-lg"
+                       href="https://www.libreccm.org">
+                        Find out more
+                    </a>
+                </#if>
             </div>
         </div>
 
-        <#if CmsPagesCategorizedItemModel.contentItem??>
+        <#if CmsPagesCategorizedItemModel.itemAvailable>
             Category has an index item
         <#else>
             Category has no index item
@@ -34,6 +46,39 @@
             <dt>view</dt>
             <dd>${view!""}</dd>
         </dl>
+
+        <h2>From <code>ArticleModel</code></h2>
+        <dl>
+            <dt>Title</dt>
+            <dd>${CmsPagesArticleModel.title}</dd>
+            <dt>Description</dt>
+            <dd>${CmsPagesArticleModel.description}</dd>
+            <dt>Text</dt>
+            <dd>${CmsPagesArticleModel.text}</dd>
+        </dl>
+
+        <h2>Item List</h2>
+        <p>Item List size: ${CmsPagesItemListModel.listSize}</p>
+        <ul>
+            <#list CmsPagesItemListModel.items as item>
+                <li>
+                    <dl>
+                        <dt>UUID</dt>
+                        <dd>${item.uuid}</dd>
+                        <dt>displayName</dt>
+                        <dd>${item.displayName}</dd>
+                        <dt>Name</dt>
+                        <dd>${item.name}</dd>
+                        <dt>Title</dt>
+                        <dd>${item.title}</dd>
+                        <dt>description</dt>
+                        <dd>${item.description}</dd>
+                        <dt>Type</dt>
+                        <dd>${item.type}</dd>
+                    </dl>
+                </li>
+            </#list>
+        </ul>
     </div>
     
 </@main.librecms>

ccm-cms/src/main/java/org/librecms/pages/models/ArticleModel.java

@@ -28,8 +28,6 @@ import javax.enterprise.context.RequestScoped;
 import javax.inject.Inject;
 import javax.inject.Named;
 import javax.transaction.Transactional;
-import javax.ws.rs.WebApplicationException;
-import javax.ws.rs.core.Response;
 
 /**
  * Model for getting the special properties of an {@link Article}. For general
@@ -39,7 +37,7 @@ import javax.ws.rs.core.Response;
  */
 @RequestScoped
 @Named("CmsPagesArticleModel")
-public class ArticleModel {
+public class ArticleModel implements ProcessesContentItem {
 
     @Inject
     private ContentItemModel contentItemModel;
@@ -47,41 +45,46 @@ public class ArticleModel {
     @Inject
     private GlobalizationHelper globalizationHelper;
     
+    private boolean initialized;
+    
     private String title;
     
     private String description;
     
     private String text;
 
+    public ArticleModel() {
+        initialized = false;
+    }
+    
     @Transactional(Transactional.TxType.REQUIRED)
     public String getTitle() {
-        if (title == null) {
+        contentItemModel.init();
-            init();
+        
-        }
         return title;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getDescription() {
-        if (description == null) {
+        contentItemModel.init();
-            init();
+
-        }
         return description;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getText() {
-        if (text == null) {
+        contentItemModel.init();
-            init();
+
-        }
         return text;
     }
     
     @Transactional(Transactional.TxType.REQUIRED)
-    protected void init() {
+    @Override
-        final ContentItem contentItem = contentItemModel
+    public void init(final ContentItem contentItem) {
-            .retrieveContentItem()
+        if (initialized) {
-            .orElse(null);
+            return;
+        }
+        
         if (contentItem instanceof Article) {
             final Article article = (Article) contentItem;
             
@@ -97,15 +100,8 @@ public class ArticleModel {
                 .ofNullable(article.getText())
                 .map(globalizationHelper::getValueFromLocalizedString)
                 .orElse("");
-        } else {
+        } 
-            throw new WebApplicationException(
+        initialized = true;
-                "Current content item is not an article.",
-                Response
-                    .status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity("Current content item is not an article.")
-                    .build()
-            );
-        }
     }
-
+    
 }

ccm-cms/src/main/java/org/librecms/pages/models/ContentItemModel.java

@@ -18,24 +18,24 @@
  */
 package org.librecms.pages.models;
 
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
-import org.libreccm.categorization.CategoryManager;
 import org.libreccm.categorization.CategoryRepository;
+import org.libreccm.core.CcmObject;
 import org.libreccm.l10n.GlobalizationHelper;
 import org.librecms.contentsection.ContentItem;
 import org.librecms.contentsection.ContentItemVersion;
+import org.librecms.pages.PagesController;
 import org.librecms.pages.PagesRouter;
 import org.librecms.pages.PagesService;
 
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
+import java.util.Iterator;
 import java.util.Optional;
 
 import javax.enterprise.context.RequestScoped;
+import javax.enterprise.inject.Instance;
 import javax.inject.Inject;
 import javax.inject.Named;
-import javax.persistence.EntityManager;
 import javax.transaction.Transactional;
 
 /**
@@ -50,162 +50,348 @@ import javax.transaction.Transactional;
 @Named("CmsPagesCategorizedItemModel")
 public class ContentItemModel {
 
-    private static final Logger LOGGER = LogManager.getLogger(
+    /**
-        ContentItemModel.class
+     * Category repository used to retrieve the current category.
-    );
+     */
-
-    @Inject
-    private CategoryManager categoryManager;
-
     @Inject
     private CategoryRepository categoryRepository;
 
+    /**
+     * Category model used to get the curretn category.
+     */
     @Inject
     private CategoryModel categoryModel;
 
-    @Inject
+    /**
-    private EntityManager entityManager;
+     * Utility for globalization stuff.
-
+     */
     @Inject
     private GlobalizationHelper globalizationHelper;
 
+    /**
+     * Provides some utility methods.
+     */
     @Inject
     private PagesService pagesService;
 
+    /**
+     * All instances of implementations of the {@link ProcessesContentItem}
+     * interface.
+     */
+    @Inject
+    private Instance<ProcessesContentItem> contentItemProcessingModels;
+
+    /**
+     * A {@link DateTimeFormatter} instance for converting dates and times to an
+     * ISO 8601 date/time string.
+     */
     private final DateTimeFormatter dateTimeFormatter
         = DateTimeFormatter.ISO_DATE_TIME.withZone(ZoneId.systemDefault());
 
+    /**
+     * The name of the item to be shown.
+     */
     private String itemName;
 
+    /**
+     * The version of the item to be shown.
+     */
     private ContentItemVersion itemVersion;
 
-//    private Optional<ContentItem> contentItem;
+    /**
+     * Data of the current content item, already prepared for retrieving the
+     * data from a MVC template. If no item with the {@link #itemName} provided
+     * by the {@link PagesController} is present in the category, the
+     * {@link Optional} will be empty.
+     */
     private Optional<ContentItemModelData> contentItem;
 
+    /**
+     * Gets the item name provided by the {@link PagesController}.
+     *
+     * @return The item name provided by the {@link PagesController}.
+     */
     public String getItemName() {
         return itemName;
     }
 
+    /**
+     * Used by the {@link PagesController} to set the name of the requested
+     * content item. May be used by other controllers.
+     *
+     * @param itemName The name of the requested content item.
+     */
     public void setItemName(final String itemName) {
         this.itemName = itemName;
     }
 
+    /**
+     * The requested version of the content item.
+     *
+     * @return The requested version of the content item.
+     */
     public ContentItemVersion getItemVersion() {
         return itemVersion;
     }
 
+    /**
+     * Used by controllers, for example the {@link PagesController} to set the
+     * requested version of the content item.
+     *
+     * @param itemVersion The requested version of the content item.
+     */
     public void setItemVersion(final ContentItemVersion itemVersion) {
         this.itemVersion = itemVersion;
     }
 
+    /**
+     * A convient getter for checking if a content item is available from a
+     * template.
+     *
+     * @return {@code true} if an item is available, {@code false} if not.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public boolean isItemAvailable() {
-       return getOrRetrieveContentItem().isPresent();
+        init();
-    }
+        return contentItem.isPresent();
-   
-    @Transactional(Transactional.TxType.REQUIRED)
-    public long getObjectId() {
-        return getOrRetrieveContentItem()
-            .map(ContentItemModelData::getObjectId)
-            .orElse(0L);
     }
 
+    /**
+     * Gets the {@code objectId)} (see {@link CcmObject#objectId} of the current
+     * item.
+     *
+     * @return The {@code objectId} of the current item if there is an item or
+     *         {@code -1L} if there is no item.
+     */
+    @Transactional(Transactional.TxType.REQUIRED)
+    public long getObjectId() {
+        init();
+        return contentItem
+            .map(ContentItemModelData::getObjectId)
+            .orElse(-1L);
+    }
+
+    /**
+     * Get the UUID of the current item (see {@link CcmObject#uuid}.
+     *
+     * @return The UUID of the current item if there is an item, an empty string
+     *         if there is not item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getUuid() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getUuid)
             .orElse("");
     }
 
+    /**
+     * Gets the display name of the current item (see
+     * {@link CcmObject#displayName}.
+     *
+     * @return The display name of the current item, or an empty string if there
+     *         is not current item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getDisplayName() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getDisplayName)
             .orElse("");
     }
 
+    /**
+     * Gets the item UUID of the current item (see {@link ContentItem#itemUuid}.
+     *
+     * @return The item UUID of the current item, or an empty string if the is
+     *         no current item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getItemUuid() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getItemUuid)
             .orElse("");
     }
 
+    /**
+     * Gets the name of the current item {@link ContentItem#name}) for the
+     * current language (see {@link GlobalizationHelper#getNegotiatedLocale()}).
+     *
+     * @return The name of the the current item for the current language, or an
+     *         empty string if there is no item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getName() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getName)
             .orElse("");
     }
 
+    /**
+     * Gets the title of the current item (see {@link ContentItem#title} for the
+     * current language (see {@link GlobalizationHelper#getNegotiatedLocale()}).
+     *
+     * @return The title of the current item for the current language, or an
+     *         empty string if there is no item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getTitle() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getTitle)
             .orElse("");
     }
 
+    /**
+     * Gets the description of the current item (see
+     * {@link ContentItem#description} for the current language (see
+     * {@link GlobalizationHelper#getNegotiatedLocale()}).
+     *
+     * @return The description of the current item for the current language, or
+     *         an empty string if there is no item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getDescription() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getDescription)
             .orElse("");
     }
 
+    /**
+     * Gets the version of the current item (see {@link ContentItem#version}.
+     *
+     * @return The version of the current version as a string, or an empty
+     *         string if there is not current item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getVersion() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getVersion)
             .orElse("");
     }
 
+    /**
+     * Gets the creation date/time of the current item (see
+     * {@link ContentItem#creationDate}.
+     *
+     * @return The creation date/time of the current item as ISO 8601 date/time
+     *         string, or an empty string if there is no item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getCreationDate() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getCreationDate)
             .orElse("");
     }
 
+    /**
+     * Gets the date/time of the last modification of the current item (see
+     * {@link ContentItem#lastModified}.
+     *
+     * @return The date/time of the modification of the current item as ISO 8601
+     *         date/time string, or an empty string of there is not current
+     *         item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getLastModified() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getLastModified)
             .orElse("");
     }
 
+    /**
+     * Gets the user name of the user that created the item.
+     *
+     * @return The user name of the user that created the item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getCreationUser() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getCreationUser)
             .orElse("");
     }
 
+    /**
+     * Gets the user name of the user that did the last modifications on the
+     * item.
+     *
+     * @return The user name of the user that did the last modifications on the
+     *         item.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
     public String getLastModifyingUserName() {
-        return getOrRetrieveContentItem()
+        init();
+        return contentItem
             .map(ContentItemModelData::getLastModifyingUserName)
             .orElse("");
     }
 
-//    public List<AttachmentList> getAttachments() {
+    /**
-//        throw new UnsupportedOperationException("Not implemented yet.");
+     * Initialize the this model and all models implementing
-//    }
+     * {@link ProcessesContentItem#}.
-//    private Optional<ContentItem> getOrRetrieveContentItem() {
+     *
-//        if (contentItem == null) {
+     * If this model has not been initalizied already this method retrieves the
-//            retrieveContentItem();
+     * current content item using {@link #retrieveContentItem()}, and
-//        }
+     * initializes {@link #contentItem} with an instance of
-//        return contentItem;
+     * {@link ContentItemModelData} build from the item using
-//    }
+     * {@link #buildModelData(org.librecms.contentsection.ContentItem)}.
+     *
+     * After that, the method will invoke the implementation of
+     * {@link ProcessesContentItem#init(org.librecms.contentsection.ContentItem)}
+     * for all available implemetentations of {@link ProcessesContentItem} (see
+     * {@link #contentItemProcessingModels}).
+     *
+     * Models implementing SHOULD call this method in their getters before
+     * returning a value. There is not need to wrap the invocation of this
+     * method in an {@code if} statement, the method will only run its logic if
+     * the item has not been initialized.
+     *
+     * If there is no current item, the method will do nothing.
+     */
     @Transactional(Transactional.TxType.REQUIRED)
-    private Optional<ContentItemModelData> getOrRetrieveContentItem() {
+    public void init() {
-        if (contentItem == null) {
+        if (contentItem != null) {
-            contentItem = retrieveContentItem().map(this::buildModelData);
+            return;
+        }
+
+        final Optional<ContentItem> item = retrieveContentItem();
+        contentItem = item.map(this::buildModelData);
+
+        final Iterator<ProcessesContentItem> iterator
+            = contentItemProcessingModels.iterator();
+        while (iterator.hasNext()) {
+            final ProcessesContentItem model = iterator.next();
+            model.init(item.orElse(null));
         }
-        return contentItem;
     }
 
+    /**
+     * Helper method for retrieving the current content item. If
+     * {@link #itemName} is {@code null} or {@code index} the method will return
+     * if the index item of the current category. If the category has not index
+     * item, an empty {@link Optional} is returned.
+     *
+     * If {@link #itemName} is <b>not</b> {@code null} or {@code index}, the
+     * method will try to find a content item associated to the category where
+     * {@link ContentItem#name} matches {@link #itemName}.
+     *
+     * @return The current content item if any, or an empyty {@link Optional}.
+     *
+     * @see PagesService#findIndexItem(org.libreccm.categorization.Category,
+     * org.librecms.contentsection.ContentItemVersion)
+     * @see
+     * PagesService#findCategorizedItem(org.libreccm.categorization.Category,
+     * java.lang.String, org.librecms.contentsection.ContentItemVersion)
+     */
     @Transactional(Transactional.TxType.REQUIRED)
-    protected Optional<ContentItem> retrieveContentItem() {
+    private Optional<ContentItem> retrieveContentItem() {
         final Optional<ContentItem> item;
         if (itemName == null || "index".equals(itemName)) {
             item = pagesService.findIndexItem(
@@ -245,6 +431,15 @@ public class ContentItemModel {
         return item;
     }
 
+    /**
+     * Helper method for building an instance {@link ContentItemModelData} for a
+     * {@link ContentItem}.
+     *
+     * @param item The source content item.
+     *
+     * @return An instance of {@link ContentItemModelData} for the provided
+     *         content item.
+     */
     private ContentItemModelData buildModelData(final ContentItem item) {
         final ContentItemModelData data = new ContentItemModelData();
         data.setObjectId(item.getObjectId());
@@ -292,6 +487,12 @@ public class ContentItemModel {
         return data;
     }
 
+    /**
+     * Encapsulates the data of content item provided by this model. To avoid to
+     * have to many fields in this model class we use an internal class to
+     * encapsulate the data. The getters of the model class return the values
+     * from an instance of this class.
+     */
     private class ContentItemModelData {
 
         private long objectId;

ccm-cms/src/main/java/org/librecms/pages/models/ContentItemTypeModel.java

@@ -43,7 +43,7 @@ import javax.transaction.Transactional;
  */
 @RequestScoped
 @Named("CmsPagesContentItemTypeModel")
-public class ContentItemTypeModel {
+public class ContentItemTypeModel implements ProcessesContentItem {
 
     @Inject
     private ContentItemModel contentItemModel;
@@ -54,48 +54,55 @@ public class ContentItemTypeModel {
     private Optional<ContentItemTypeModelData> contentType;
 
     public long getContentTypeId() {
-        return getOrRetrieveContentType()
+        contentItemModel.init();
+
+        return contentType
             .map(ContentItemTypeModelData::getTypeId)
             .orElse(0L);
     }
 
     public String getUuid() {
-        return getOrRetrieveContentType()
+        contentItemModel.init();
+
+        return contentType
             .map(ContentItemTypeModelData::getUuid)
             .orElse("");
     }
 
     public String getDisplayName() {
-        return getOrRetrieveContentType()
+        contentItemModel.init();
+
+        return contentType
             .map(ContentItemTypeModelData::getDisplayName)
             .orElse("");
     }
 
     public String getLabel() {
-        return getOrRetrieveContentType()
+        contentItemModel.init();
+
+        return contentType
             .map(ContentItemTypeModelData::getLabel)
             .orElse("");
     }
 
     public String getDescription() {
-        return getOrRetrieveContentType()
+        contentItemModel.init();
+
+        return contentType
             .map(ContentItemTypeModelData::getDescription)
             .orElse("");
     }
 
-    private Optional<ContentItemTypeModelData> getOrRetrieveContentType() {
-        if (contentType == null) {
-            retrieveContentType();
-        }
-        return contentType;
-    }
-
     @Transactional(Transactional.TxType.REQUIRED)
-    private void retrieveContentType() {
+    public void init(final ContentItem contentItem) {
-        contentType = contentItemModel.retrieveContentItem()
+        if (contentType != null) {
+            return;
+        }
+
+        contentType = Optional
+            .ofNullable(contentItem)
             .map(ContentItem::getContentType)
             .map(this::buildModelData);
-
     }
 
     @Transactional(Transactional.TxType.REQUIRED)

ccm-cms/src/main/java/org/librecms/pages/models/EventModel.java

@@ -31,8 +31,6 @@ import javax.enterprise.context.RequestScoped;
 import javax.inject.Inject;
 import javax.inject.Named;
 import javax.transaction.Transactional;
-import javax.ws.rs.WebApplicationException;
-import javax.ws.rs.core.Response;
 
 /**
  *
@@ -40,7 +38,7 @@ import javax.ws.rs.core.Response;
  */
 @RequestScoped
 @Named("CmsPagesEventModel")
-public class EventModel {
+public class EventModel implements ProcessesContentItem {
 
     @Inject
     private ContentItemModel contentItemModel;
@@ -48,6 +46,8 @@ public class EventModel {
     @Inject
     private GlobalizationHelper globalizationHelper;
 
+    private boolean initialized;
+
     private final DateTimeFormatter isoDateTimeFormatter;
 
     private String title;
@@ -65,77 +65,67 @@ public class EventModel {
     private String eventType;
 
     public EventModel() {
+        initialized = false;
         isoDateTimeFormatter = DateTimeFormatter.ISO_DATE_TIME
             .withZone(ZoneId.systemDefault());
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getTitle() {
-        if (title == null) {
+        contentItemModel.init();
-            init();
-        }
 
         return title;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getText() {
-        if (text == null) {
+        contentItemModel.init();
-            init();
-        }
 
         return text;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getStartDateTime() {
-        if (startDateTime == null) {
+        contentItemModel.init();
-            init();
-        }
 
         return startDateTime;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getEndDateTime() {
-        if (endDateTime == null) {
+        contentItemModel.init();
-            init();
-        }
 
         return endDateTime;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getEventDate() {
-        if (eventDate == null) {
+        contentItemModel.init();
-            init();
+
-        }
         return eventDate;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getLocation() {
-        if (location == null) {
+        contentItemModel.init();
-            init();
-        }
 
         return location;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getEventType() {
-        if (eventType == null) {
+        contentItemModel.init();
-            init();
-        }
 
-        return eventDate;
+        return eventType;
     }
 
+    @Override
     @Transactional(Transactional.TxType.REQUIRED)
-    protected void init() {
+    public void init(final ContentItem contentItem) {
-        final ContentItem contentItem = contentItemModel
+        if (initialized) {
-            .retrieveContentItem()
+            return;
-            .orElse(null);
+        }
+
         if (contentItem instanceof Event) {
             final Event event = (Event) contentItem;
 
@@ -169,15 +159,9 @@ public class EventModel {
                 .ofNullable(event.getEventType())
                 .map(globalizationHelper::getValueFromLocalizedString)
                 .orElse("");
-        } else {
-            throw new WebApplicationException(
-                "Current content item is not an event",
-                Response
-                    .status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity("Current content item is not an event.")
-                    .build()
-            );
         }
+
+        initialized = true;
     }
 
 }

ccm-cms/src/main/java/org/librecms/pages/models/MultiPartArticleModel.java

@@ -41,7 +41,7 @@ import javax.ws.rs.core.Response;
  */
 @RequestScoped
 @Named("CmsPagesMultiPartArticleModel")
-public class MultiPartArticleModel {
+public class MultiPartArticleModel implements ProcessesContentItem {
 
     @Inject
     private ContentItemModel contentItemModel;
@@ -49,6 +49,8 @@ public class MultiPartArticleModel {
     @Inject
     private GlobalizationHelper globalizationHelper;
 
+    private boolean initialized;
+
     @Inject
     private PageUrlModel pageUrlModel;
 
@@ -61,69 +63,62 @@ public class MultiPartArticleModel {
     private String currentSectionTitle;
 
     private String currentSectionText;
-    
+
     private List<MultiPartArticleSectionModel> sections;
 
+    public MultiPartArticleModel() {
+        initialized = false;
+    }
+
     @Transactional(Transactional.TxType.REQUIRED)
     public String getTitle() {
-        if (title == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return title;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getSummary() {
-        if (summary == null)  {
+        contentItemModel.init();
-            return null;
+
-        }
-        
         return summary;
     }
 
-    
     @Transactional(Transactional.TxType.REQUIRED)
     public List<String> getSectionTitles() {
-        if (sectionTitles == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return Collections.unmodifiableList(sectionTitles);
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getCurrentSectionTitle() {
-        if (currentSectionTitle == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return currentSectionTitle;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getCurrentSectionText() {
-        if (currentSectionText == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return currentSectionText;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public List<MultiPartArticleSectionModel> getSections() {
-        if (sections == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return Collections.unmodifiableList(sections);
     }
 
+    @Override
     @Transactional(Transactional.TxType.REQUIRED)
-    protected void init() {
+    public void init(final ContentItem contentItem) {
-        final ContentItem contentItem = contentItemModel
+        if (initialized) {
-            .retrieveContentItem()
+            return;
-            .orElse(null);
+        }
+
         if (contentItem instanceof MultiPartArticle) {
             final MultiPartArticle mpa = (MultiPartArticle) contentItem;
 
@@ -165,26 +160,20 @@ public class MultiPartArticleModel {
                 .ofNullable(mpa.getSections().get(currentSection).getTitle())
                 .map(globalizationHelper::getValueFromLocalizedString)
                 .orElse("");
-            
+
             currentSectionText = Optional
                 .ofNullable(mpa.getSections().get(currentSection).getText())
                 .map(globalizationHelper::getValueFromLocalizedString)
                 .orElse("");
-            
+
             sections = mpa
                 .getSections()
                 .stream()
                 .map(this::buildSectionModel)
                 .collect(Collectors.toList());
-        } else {
-            throw new WebApplicationException(
-                "Current content item is not an MultiPartArticle",
-                Response
-                    .status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity("Current content item is not an MultiPartArticle.")
-                    .build()
-            );
         }
+
+        initialized = true;
     }
 
     private int readCurrentSection() {

ccm-cms/src/main/java/org/librecms/pages/models/NewsModel.java

@@ -22,7 +22,6 @@ import org.libreccm.l10n.GlobalizationHelper;
 import org.librecms.contentsection.ContentItem;
 import org.librecms.contenttypes.News;
 
-import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.util.Date;
@@ -32,8 +31,6 @@ import javax.enterprise.context.RequestScoped;
 import javax.inject.Inject;
 import javax.inject.Named;
 import javax.transaction.Transactional;
-import javax.ws.rs.WebApplicationException;
-import javax.ws.rs.core.Response;
 
 /**
  *
@@ -41,79 +38,79 @@ import javax.ws.rs.core.Response;
  */
 @RequestScoped
 @Named("CmsPagesNewsModel")
-public class NewsModel {
+public class NewsModel implements ProcessesContentItem {
 
     @Inject
     private ContentItemModel contentItemModel;
 
     @Inject
     private GlobalizationHelper globalizationHelper;
-    
+
+    private boolean initialized;
+
     private final DateTimeFormatter isoDateTimeFormatter;
-    
+
     private String title;
-    
+
     private String description;
-    
+
     private String text;
-    
+
     private String releaseDateTime;
-    
+
     private boolean homepage;
-    
+
     public NewsModel() {
+        initialized = false;
         isoDateTimeFormatter = DateTimeFormatter.ISO_DATE_TIME
             .withZone(ZoneId.systemDefault());
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getTitle() {
-        if (title == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return title;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getDescription() {
-        if (description == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return description;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getText() {
-        if (text == null) {
+        contentItemModel.init();
-            init();
+
-        }
         return text;
     }
 
     @Transactional(Transactional.TxType.REQUIRED)
     public String getReleaseDateTime() {
-        if (releaseDateTime == null) {
+        contentItemModel.init();
-            init();
+
-        }
-        
         return releaseDateTime;
     }
-    
-    @Transactional(Transactional.TxType.REQUIRED)
-    public boolean getHomepage() {
-        return homepage;
-    }
 
     @Transactional(Transactional.TxType.REQUIRED)
-    protected void init() {
+    public boolean getHomepage() {
-        final ContentItem contentItem = contentItemModel
+        contentItemModel.init();
-            .retrieveContentItem()
+
-            .orElse(null);
+        return homepage;
+    }
+
+    @Override
+    @Transactional(Transactional.TxType.REQUIRED)
+    public void init(final ContentItem contentItem) {
+        if (initialized) {
+            return;
+        }
+
         if (contentItem instanceof News) {
-            final News news =  (News) contentItem;
+            final News news = (News) contentItem;
-            
+
             title = Optional
                 .ofNullable(news.getTitle())
                 .map(globalizationHelper::getValueFromLocalizedString)
@@ -132,15 +129,9 @@ public class NewsModel {
                 .map(isoDateTimeFormatter::format)
                 .orElse("");
             homepage = news.isHomepage();
-        } else {
-            throw new WebApplicationException(
-                "Current content item is not a news item.",
-                Response
-                    .status(Response.Status.INTERNAL_SERVER_ERROR)
-                    .entity("Current content item is not a new item.")
-                    .build()
-            );
         }
+
+        initialized = true;
     }
 
 }

ccm-cms/src/main/java/org/librecms/pages/models/ProcessesContentItem.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2022 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.librecms.pages.models;
+
+import org.hibernate.LazyInitializationException;
+import org.librecms.contentsection.ContentItem;
+
+import javax.transaction.Transactional;
+
+/**
+ * Models that provide data for the current content item (either the index item
+ * of a category or a selected content item) SHOULD implement this interface.
+ *
+ * This {@link ContentItemModel} collects all instances of classes implementing
+ * this interface and calls their implemententation of the
+ * {@link #init(org.librecms.contentsection.ContentItem)} method.
+ *
+ * For an example of an implementation please look at
+ * {@link ContentItemTypeModel}, {@link ArticleModel} or
+ * at {@link MultiPartArticleModel} for a more complex model.
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public interface ProcessesContentItem {
+
+    /**
+     * Initalizes a model providing the data of a content item for MVC
+     * templates.
+     *
+     * If the implementing model only provides data for specific sub classes of
+     * {@link ContentItem} the implementation MUST check the correct type using
+     * the {@code instanceof} operator. If the item is not a the correct type a
+     * implementation MUST gracefully ignore the item.
+     *
+     * To avoid a {@link LazyInitializationException} implementations SHOULD be
+     * annotated with {@link Transactional} and the
+     * {@link Transactional.TxType#REQUIRED}.
+     *
+     * @param item The item.
+     */
+    void init(ContentItem item);
+
+}