0032039: Add generic mechanism to have multiple cached preferences

diff --git a/modules/org.openbravo.client.application/src/org/openbravo/client/application/CachedPreference.java b/modules/org.openbravo.client.application/src/org/openbravo/client/application/CachedPreference.java
new file mode 100644
--- /dev/null
+++ b/modules/org.openbravo.client.application/src/org/openbravo/client/application/CachedPreference.java
@@ -0,0 +1,139 @@
+/*
+ *************************************************************************
+ * The contents of this file are subject to the Openbravo  Public  License
+ * Version  1.1  (the  "License"),  being   the  Mozilla   Public  License
+ * Version 1.1  with a permitted attribution clause; you may not  use this
+ * file except in compliance with the License. You  may  obtain  a copy of
+ * the License at http://www.openbravo.com/legal/license.html 
+ * Software distributed under the License  is  distributed  on  an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
+ * License for the specific  language  governing  rights  and  limitations
+ * under the License. 
+ * The Original Code is Openbravo ERP. 
+ * The Initial Developer of the Original Code is Openbravo SLU 
+ * All portions are Copyright (C) 2016 Openbravo SLU 
+ * All Rights Reserved. 
+ * Contributor(s):  ______________________________________.
+ ************************************************************************
+ */
+package org.openbravo.client.application;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.enterprise.context.ApplicationScoped;
+
+import org.openbravo.dal.core.OBContext;
+import org.openbravo.dal.service.OBDal;
+import org.openbravo.erpCommon.businessUtility.Preferences;
+import org.openbravo.erpCommon.utility.PropertyException;
+import org.openbravo.model.ad.system.Client;
+import org.openbravo.model.common.enterprise.Organization;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This class is used as a singleton to keep the value of some preferences in cache during the
+ * application life cycle, avoiding the time spent to compute the preference value. The preference
+ * values that can be cached by this class are those defined at System level.
+ * 
+ * This class it is also used by the
+ * {@link org.openbravo.client.application.event.PreferenceEventHandler} class to detect changes in
+ * the cached preferences values, and it that case it invalidates the stored value. This way the
+ * next time it is requested, the current value will be retrieved from database again.
+ * 
+ * This mechanism for automatic refresh the preference value, only works on environments with a
+ * single JVM. In case of Tomcat clustering environments (multiple JVM) it will be necessary to
+ * restart Tomcat to retrieve the new value of the preference in every JVM.
+ * 
+ */
+@ApplicationScoped
+public class CachedPreference {
+  private static final Logger log = LoggerFactory.getLogger(CachedPreference.class);
+  private List<String> propertyList = new ArrayList<String>(
+      Arrays.asList("OBJSON_AllowUnpagedDatasourceManualRequest"));
+  private Map<String, String> cachedPreference = new HashMap<String, String>();
+
+  /**
+   * It returns a String with the value of the preference whose related property name is entered as
+   * parameter. In case the value is not stored in cache, then the value will be retrieved from
+   * database.
+   * 
+   * @param propertyName
+   *          The name of the property related to the preference
+   * 
+   * @return A String with the value of the cached preference
+   */
+  public String getPreferenceValue(String propertyName) {
+    long t = System.nanoTime();
+    if (!cachedPreference.containsKey(propertyName)) {
+      try {
+        OBContext.setAdminMode(false);
+        Client systemClient = OBDal.getInstance().get(Client.class, "0");
+        Organization asterisk = OBDal.getInstance().get(Organization.class, "0");
+        String value = Preferences.getPreferenceValue(propertyName, true, systemClient, asterisk,
+            null, null, null);
+        setPreferenceValue(propertyName, value);
+      } catch (PropertyException ignore) {
+        // Ignore the exception, caused because the preference was not found
+        setPreferenceValue(propertyName, null);
+      } finally {
+        OBContext.restorePreviousMode();
+      }
+    }
+    log.debug("preference value retrieved in {} ns", (System.nanoTime() - t));
+    return cachedPreference.get(propertyName);
+  }
+
+  /**
+   * Checks if the preference related to the property name entered as parameter is contained in the
+   * list of cached preferences.
+   * 
+   * @param propertyName
+   *          The name of the property related to the preference
+   * @return true if the preference related to the property name is a cached preference, false
+   *         otherwise
+   */
+  public boolean isCachedPreference(String propertyName) {
+    return propertyList.contains(propertyName);
+  }
+
+  /**
+   * Sets the cached value of the preference. This method is defined as synchronized in order to
+   * avoid concurrency problems.
+   * 
+   * @param propertyName
+   *          The name of the property related to the preference
+   * @param preferenceValue
+   *          String with the value assigned to the preference
+   */
+  public synchronized void setPreferenceValue(String propertyName, String preferenceValue) {
+    this.cachedPreference.put(propertyName, preferenceValue);
+  }
+
+  /**
+   * Invalidates the cached value of the preference. This method is defined as synchronized in order
+   * to avoid concurrency problems.
+   * 
+   * @param propertyName
+   *          The name of the property related to the preference
+   */
+  public synchronized void invalidatePreferenceValue(String propertyName) {
+    this.cachedPreference.remove(propertyName);
+  }
+
+  /**
+   * Adds a new preference into the set of preferences whose value is stored in cache.
+   * 
+   * @param propertyName
+   *          The name of the property related to the preference to be cached
+   */
+  public void addCachedPreference(String propertyName) {
+    if (!isCachedPreference(propertyName)) {
+      propertyList.add(propertyName);
+    }
+  }
+}
diff --git a/modules/org.openbravo.client.application/src/org/openbravo/client/application/event/PreferenceEventHandler.java b/modules/org.openbravo.client.application/src/org/openbravo/client/application/event/PreferenceEventHandler.java
--- a/modules/org.openbravo.client.application/src/org/openbravo/client/application/event/PreferenceEventHandler.java
+++ b/modules/org.openbravo.client.application/src/org/openbravo/client/application/event/PreferenceEventHandler.java
@@ -11,7 +11,7 @@
  * under the License.
  * The Original Code is Openbravo ERP.
  * The Initial Developer of the Original Code is Openbravo SLU
- * All portions are Copyright (C) 2015 Openbravo SLU
+ * All portions are Copyright (C) 2015-2016 Openbravo SLU
  * All Rights Reserved.
  * Contributor(s):  ______________________________________.
  ************************************************************************
@@ -25,20 +25,16 @@
 import org.apache.log4j.Logger;
 import org.openbravo.base.model.Entity;
 import org.openbravo.base.model.ModelProvider;
+import org.openbravo.client.application.CachedPreference;
 import org.openbravo.client.kernel.event.EntityDeleteEvent;
 import org.openbravo.client.kernel.event.EntityNewEvent;
 import org.openbravo.client.kernel.event.EntityPersistenceEventObserver;
 import org.openbravo.client.kernel.event.EntityUpdateEvent;
 import org.openbravo.model.ad.domain.Preference;
-import org.openbravo.service.json.UnpagedRequestCachedPreference;
 
 /**
  * Listens to delete, update and save events for the {@link Preference} entity. If it detects a
- * change in the 'OBJSON_AllowUnpagedDatasourceManualRequest' preference it invalidates its cached
- * value by setting it to null.
- * 
- * {@link "https://issues.openbravo.com/view.php?id=30204"}
- * 
+ * change in any of the cached preferences it invalidates its cached value.
  */
 public class PreferenceEventHandler extends EntityPersistenceEventObserver {
 
@@ -46,7 +42,7 @@
       .getEntity(Preference.ENTITY_NAME) };
   protected Logger logger = Logger.getLogger(this.getClass());
   @Inject
-  private UnpagedRequestCachedPreference unpagedRequestPreference;
+  private CachedPreference cachedPreference;
 
   @Override
   protected Entity[] getObservedEntities() {
@@ -58,9 +54,7 @@
       return;
     }
     final Preference preference = (Preference) event.getTargetInstance();
-    if (unpagedRequestPreference.getProperty().equals(preference.getProperty())) {
-      unpagedRequestPreference.setPreferenceValue(null);
-    }
+    invalidateCachedPreferenceValue(preference.getProperty());
   }
 
   public void onUpdate(@Observes EntityUpdateEvent event) {
@@ -68,9 +62,7 @@
       return;
     }
     final Preference preference = (Preference) event.getTargetInstance();
-    if (unpagedRequestPreference.getProperty().equals(preference.getProperty())) {
-      unpagedRequestPreference.setPreferenceValue(null);
-    }
+    invalidateCachedPreferenceValue(preference.getProperty());
   }
 
   public void onDelete(@Observes EntityDeleteEvent event) {
@@ -78,8 +70,12 @@
       return;
     }
     final Preference preference = (Preference) event.getTargetInstance();
-    if (unpagedRequestPreference.getProperty().equals(preference.getProperty())) {
-      unpagedRequestPreference.setPreferenceValue(null);
+    invalidateCachedPreferenceValue(preference.getProperty());
+  }
+
+  private void invalidateCachedPreferenceValue(String property) {
+    if (cachedPreference.isCachedPreference(property)) {
+      cachedPreference.invalidatePreferenceValue(property);
     }
   }
 }
diff --git a/modules/org.openbravo.service.json/src/org/openbravo/service/json/DefaultJsonDataService.java b/modules/org.openbravo.service.json/src/org/openbravo/service/json/DefaultJsonDataService.java
--- a/modules/org.openbravo.service.json/src/org/openbravo/service/json/DefaultJsonDataService.java
+++ b/modules/org.openbravo.service.json/src/org/openbravo/service/json/DefaultJsonDataService.java
@@ -11,7 +11,7 @@
  * under the License. 
  * The Original Code is Openbravo ERP. 
  * The Initial Developer of the Original Code is Openbravo SLU 
- * All portions are Copyright (C) 2009-2015 Openbravo SLU 
+ * All portions are Copyright (C) 2009-2016 Openbravo SLU 
  * All Rights Reserved. 
  * Contributor(s):  ______________________________________.
  ************************************************************************
@@ -42,6 +42,7 @@
 import org.openbravo.base.structure.BaseOBObject;
 import org.openbravo.base.util.Check;
 import org.openbravo.base.weld.WeldUtils;
+import org.openbravo.client.application.CachedPreference;
 import org.openbravo.dal.core.DalUtil;
 import org.openbravo.dal.core.OBContext;
 import org.openbravo.dal.service.OBDal;
@@ -73,8 +74,10 @@
 
   private static final String ADD_FLAG = "_doingAdd";
 
+  private static final String ALLOW_UNPAGED_DS_MANUAL_REQUEST = "OBJSON_AllowUnpagedDatasourceManualRequest";
+
   @Inject
-  private UnpagedRequestCachedPreference unpagedRequestPreference;
+  private CachedPreference cachedPreference;
 
   private static DefaultJsonDataService instance = WeldUtils
       .getInstanceFromStaticBeanManager(DefaultJsonDataService.class);
@@ -473,7 +476,8 @@
 
         // for standard tab and selector datasources pagination is mandatory
         throw new OBException(OBMessageUtils.messageBD("OBJSON_NoPagedFetch"));
-      } else if (!"Y".equals(unpagedRequestPreference.getPreferenceValue()) && !isWsCall) {
+      } else if (!"Y".equals(cachedPreference.getPreferenceValue(ALLOW_UNPAGED_DS_MANUAL_REQUEST))
+          && !isWsCall) {
         throw new OBException(OBMessageUtils.messageBD("OBJSON_NoPagedFetchManual"));
       }
     }