Added extension-point for LockManager. Added option for specifying max value for version-number when using version-number strategy with optimistic locking.

src/main/java/org/datanucleus/ExecutionContextImpl.java

@@ -352,13 +352,39 @@ protected Object initialValue()
             pbrAtCommitHandler = new ReachabilityAtCommitHandler(this);
         }
 
-        lockMgr = new LockManagerImpl(this);
+        lockMgr = createLockManager();
 
         l2CacheObjectsToEvictUponRollback = null;
 
         setLevel2Cache(true);
     }
 
+    private LockManager createLockManager()
+    {
+        String lockManagerType = nucCtx.getConfiguration().getStringProperty(PropertyNames.PROPERTY_LOCKMANAGER_TYPE);
+        if (lockManagerType != null && !lockManagerType.isEmpty())
+        {
+            final Object tmpLocManager;
+            try
+            {
+                // Create an instance of the lock manager
+                tmpLocManager = nucCtx.getPluginManager().createExecutableExtension("org.datanucleus.lockmanager", "name", lockManagerType, "class-name",
+                        new Class[]{ExecutionContext.class}, new Object[]{this});
+            }
+            catch (Exception e)
+            {
+                // Class name for this lockmanager plugin is not found!
+                throw new NucleusUserException("Failed to create requested lock manager: " + lockManagerType, e).setFatal();
+            }
+            if (tmpLocManager instanceof LockManager)
+            {
+                return (LockManager) tmpLocManager;
+            }
+            throw new NucleusUserException("Requested lock manager not found: " + lockManagerType).setFatal();
+        }
+        return new LockManagerImpl(this);
+    }
+
     /**
      * Method to close the context.
      */

src/main/java/org/datanucleus/PropertyNames.java

@@ -252,4 +252,5 @@ public class PropertyNames
     public static final String PROPERTY_QUERY_RESULTCACHE_VALIDATEOBJECTS = "datanucleus.query.resultcache.validateobjects";
     public static final String PROPERTY_QUERY_RESULT_SIZE_METHOD = "datanucleus.query.resultsizemethod";
     public static final String PROPERTY_QUERY_COMPILE_NAMED_QUERIES_AT_STARTUP = "datanucleus.query.compilenamedqueriesatstartup";
+    public static final String PROPERTY_LOCKMANAGER_TYPE = "datanucleus.lockmanager.type";
 }

src/main/java/org/datanucleus/metadata/MetaData.java

@@ -112,6 +112,9 @@ private enum State
     /** Class : initial value to use for this class for versioning (when using version-number strategy). */
     public static final String EXTENSION_VERSION_NUMBER_INITIAL_VALUE = "version-initial-value";
 
+    /** Class : max value for version field before rolling over to initial value again (when using version-number strategy). */
+    public static final String EXTENSION_VERSION_NUMBER_MAX_VALUE = "version-max-value";
+
     /** Member : name of type converter to use. */
     public final static String EXTENSION_MEMBER_TYPE_CONVERTER_NAME = "type-converter-name";
 

src/main/java/org/datanucleus/state/LockManagerImpl.java

@@ -39,13 +39,13 @@
  */
 public class LockManagerImpl implements LockManager
 {
-    ExecutionContext ec;
+    protected final ExecutionContext ec;
 
     /** Map of lock mode, keyed by the object identity. Utilised on a find operation. */
-    Map<Object, LockMode> requiredLockModesById = null;
+    private Map<Object, LockMode> requiredLockModesById = null;
 
     /** Map of lock mode, keyed by StateManager. */
-    Map<DNStateManager, LockMode> lockModeBySM = null;
+    private Map<DNStateManager, LockMode> lockModeBySM = null;
 
     public LockManagerImpl(ExecutionContext ec)
     {
@@ -282,7 +282,15 @@ else if (java.time.Instant.class.isAssignableFrom(verMmd.getType()))
         }
         else if (versionStrategy == VersionStrategy.VERSION_NUMBER)
         {
-            if (currentVersion == null)
+            // First check if a max-value is defined in version-meta-data
+            // and if so then check if we should roll over - back to initial value.
+            Integer maxValue = null;
+            if (vermd.hasExtension(MetaData.EXTENSION_VERSION_NUMBER_MAX_VALUE))
+            {
+                maxValue = Integer.valueOf(vermd.getValueForExtension(MetaData.EXTENSION_VERSION_NUMBER_MAX_VALUE));
+            }
+            if (currentVersion == null ||
+                    (maxValue != null && currentVersion instanceof Number && ((Number)currentVersion).intValue() >= maxValue))
             {
                 // Get the initial value from the VersionMetaData extension if provided, otherwise the global default (for the context)
                 Integer initValue = null;

src/main/resources/plugin.xml

@@ -51,6 +51,7 @@ Contributors:
     <extension-point id="class_annotation_handler" name="Class Annotation Handler" schema="schema/class_annotation_handler.exsd"/>
     <extension-point id="member_annotation_handler" name="Member Annotation Handler" schema="schema/member_annotation_handler.exsd"/>
     <extension-point id="identifier_namingfactory" name="Identifier NamingFactory" schema="schema/identifier_namingfactory.exsd"/>
+    <extension-point id="lockmanager" name="Lock Manager" schema="schema/lockmanager.exsd"/>
 
     <!-- XML METADATA ENTITY RESOLVERS -->
     <extension point="org.datanucleus.metadata_entityresolver">

src/main/resources/schema/lockmanager.exsd

@@ -0,0 +1,112 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!-- Schema file written by PDE -->
+<schema targetNamespace="org.datanucleus">
+<annotation>
+      <appInfo>
+         <meta.schema plugin="org.datanucleus" id="lockmanager" name="Lock Manager"/>
+      </appInfo>
+      <documentation>
+         [Enter description of this extension point.]
+      </documentation>
+   </annotation>
+
+   <element name="extension">
+      <complexType>
+         <sequence>
+            <element ref="lockmanager" minOccurs="1" maxOccurs="unbounded"/>
+         </sequence>
+         <attribute name="point" type="string" use="required">
+            <annotation>
+               <documentation>
+
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="id" type="string">
+            <annotation>
+               <documentation>
+
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="name" type="string">
+            <annotation>
+               <documentation>
+
+               </documentation>
+               <appInfo>
+                  <meta.attribute translatable="true"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <element name="lockmanager">
+      <complexType>
+         <attribute name="name" type="string" use="required">
+            <annotation>
+               <documentation>
+
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="class-name" type="string" use="required">
+            <annotation>
+               <documentation>
+
+               </documentation>
+               <appInfo>
+                  <meta.attribute kind="java" basedOn="org.datanucleus.state.LockManager"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="since"/>
+      </appInfo>
+      <documentation>
+         [Enter the first release in which this extension point appears.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="examples"/>
+      </appInfo>
+      <documentation>
+         [Enter extension point usage example here.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="apiInfo"/>
+      </appInfo>
+      <documentation>
+         [Enter API information here.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="implementation"/>
+      </appInfo>
+      <documentation>
+         [Enter information about supplied implementation of this extension point.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="copyright"/>
+      </appInfo>
+      <documentation>
+
+      </documentation>
+   </annotation>
+
+</schema>