Package com.db4o.internal.config

Class CommonConfigurationImpl

    • Constructor Detail

      • CommonConfigurationImpl

        public CommonConfigurationImpl​(Config4Impl config)

    • Method Detail

      • activationDepth

        public void activationDepth​(int depth)
        Description copied from interface: CommonConfiguration
        sets the activation depth to the specified value.

        Why activation?
        When objects are instantiated from the database, the instantiation of member objects needs to be limited to a certain depth. Otherwise a single object could lead to loading the complete database into memory, if all objects where reachable from a single root object.

        db4o uses the concept "depth", the number of field-to-field hops an object is away from another object. The preconfigured "activation depth" db4o uses in the default setting is 5.

        Whenever an application iterates through the ObjectSet of a query result, the result objects will be activated to the configured activation depth.

        A concrete example with the preconfigured activation depth of 5:
         // Object foo is the result of a query, it is delivered by the ObjectSet 
 Object foo = objectSet.next();
        foo.member1.member2.member3.member4.member5 will be a valid object
        foo, member1, member2, member3 and member4 will be activated
        member5 will be deactivated, all of it's members will be null
        member5 can be activated at any time by calling ObjectContainer#activate(member5, depth).

        Note that raising the global activation depth will consume more memory and have negative effects on the performance of first-time retrievals. Lowering the global activation depth needs more individual activation work but can increase performance of queries.

        ObjectContainer#deactivate(Object, depth) can be used to manually free memory by deactivating objects.

        In client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        activationDepth in interface CommonConfiguration
        Parameters:
        depth - the desired global activation depth.
        See Also:
        configuring classes individually

      • add

        public void add​(ConfigurationItem configurationItem)
        Description copied from interface: CommonConfiguration
        adds ConfigurationItems to be applied when an ObjectContainer or ObjectServer is opened.
        Specified by:
        add in interface CommonConfiguration
        Parameters:
        configurationItem - the ConfigurationItem

      • addAlias

        public void addAlias​(Alias alias)
        Description copied from interface: CommonConfiguration
        adds a new Alias for a class, namespace or package.

        Aliases can be used to persist classes in the running application to different persistent classes in a database file or on a db4o server.

        Two simple Alias implementations are supplied along with db4o:
        - TypeAlias provides an #equals() resolver to match names directly.
        - WildcardAlias allows simple pattern matching with one single '*' wildcard character.

        It is possible to create own complex Alias constructs by creating own resolvers that implement the Alias interface.

        Examples of concrete usecases:

        // Creating an Alias for a single class
        EmbeddedConfiguration config = Db4oEmbedded.newConfiguration(); config.common().addAlias(
          new TypeAlias("com.f1.Pilot", "com.f1.Driver"));


        // Mapping a Java package onto another
        config.common().addAlias(
          new WildcardAlias(
            "com.f1.*",
            "com.f1.client*"));

        Aliases that translate the persistent name of a class to a name that already exists as a persistent name in the database (or on the server) are not permitted and will throw an exception when the database file is opened.

        Aliases should be configured before opening a database file or connecting to a server.

        In client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        addAlias in interface CommonConfiguration

      • allowVersionUpdates

        public void allowVersionUpdates​(boolean flag)
        Description copied from interface: CommonConfiguration
        turns automatic database file format version updates on.

        Upon db4o database file format version changes, db4o can automatically update database files to the current version. db4objects does not provide functionality to reverse this process. It is not ensured that updated database files can be read with older db4o versions. In some cases (Example: using ObjectManager) it may not be desirable to update database files automatically therefore automatic updating is turned off by default for security reasons.

        Call this method to turn automatic database file version updating on.

        If automatic updating is turned off, db4o will refuse to open database files that use an older database file format.

        In client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        allowVersionUpdates in interface CommonConfiguration

      • automaticShutDown

        public void automaticShutDown​(boolean flag)
        Description copied from interface: CommonConfiguration
        turns automatic shutdown of the engine on and off. The default and recommended setting is true.
        Specified by:
        automaticShutDown in interface CommonConfiguration
        Parameters:
        flag - whether db4o should shut down automatically.

      • bTreeNodeSize

        public void bTreeNodeSize​(int size)
        Description copied from interface: CommonConfiguration
        configures the size of BTree nodes in indexes.

        Default setting: 100
        Lower values will allow a lower memory footprint and more efficient reading and writing of small slots.
        Higher values will reduce the overall number of read and write operations and allow better performance at the cost of more RAM use.

        In client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        bTreeNodeSize in interface CommonConfiguration
        Parameters:
        size - the number of elements held in one BTree node.

      • callbacks

        public void callbacks​(boolean flag)
        Description copied from interface: CommonConfiguration
        turns callback methods on and off.

        Callbacks are turned on by default.

        A tuning hint: If callbacks are not used, you can turn this feature off, to prevent db4o from looking for callback methods in persistent classes. This will increase the performance on system startup.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        callbacks in interface CommonConfiguration
        Parameters:
        flag - false to turn callback methods off
        See Also:
        Using callbacks

      • callbackMode

        public void callbackMode​(CallBackMode mode)

      • callConstructors

        public void callConstructors​(boolean flag)
        Description copied from interface: CommonConfiguration
        advises db4o to try instantiating objects with/without calling constructors.

        Not all JDKs / .NET-environments support this feature. db4o will attempt, to follow the setting as good as the enviroment supports. In doing so, it may call implementation-specific features like sun.reflect.ReflectionFactory#newConstructorForSerialization on the Sun Java 1.4.x/5 VM (not available on other VMs) and FormatterServices.GetUninitializedObject() on the .NET framework (not available on CompactFramework). This setting may also be overridden for individual classes in ObjectClass.callConstructor(boolean).

        The default setting depends on the features supported by your current environment.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Specified by:
        callConstructors in interface CommonConfiguration
        Parameters:
        flag - - specify true, to request calling constructors, specify false to request not calling constructors.
        See Also:
        ObjectClass.callConstructor(boolean)

      • detectSchemaChanges

        public void detectSchemaChanges​(boolean flag)
        Description copied from interface: CommonConfiguration
        tuning feature: configures whether db4o checks all persistent classes upon system startup, for added or removed fields.

        If this configuration setting is set to false while a database is being created, members of classes will not be detected and stored.

        This setting can be set to false in a production environment after all persistent classes have been stored at least once and classes will not be modified any further in the future.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Default value: true
        Specified by:
        detectSchemaChanges in interface CommonConfiguration
        Parameters:
        flag - the desired setting

      • exceptionsOnNotStorable

        public void exceptionsOnNotStorable​(boolean flag)
        Description copied from interface: CommonConfiguration
        configures whether Exceptions are to be thrown, if objects can not be stored.

        db4o requires the presence of a constructor that can be used to instantiate objects. If no default public constructor is present, all available constructors are tested, whether an instance of the class can be instantiated. Null is passed to all constructor parameters. The first constructor that is successfully tested will be used throughout the running db4o session. If an instance of the class can not be instantiated, the object will not be stored. By default, execution will be stopped with an Exception. This method can be used to configure db4o to not throw an ObjectNotStorableException if an object can not be stored.

        The default for this setting is true.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Specified by:
        exceptionsOnNotStorable in interface CommonConfiguration
        Parameters:
        flag - true to throw Exceptions if objects can not be stored.

      • internStrings

        public void internStrings​(boolean flag)
        Description copied from interface: CommonConfiguration
        configures db4o to call #intern() on strings upon retrieval. In a client/server environment it is good practice to configure the client and the server in exactly the same way.
        Specified by:
        internStrings in interface CommonConfiguration
        Parameters:
        flag - true to intern strings

      • markTransient

        public void markTransient​(java.lang.String attributeName)
        Description copied from interface: CommonConfiguration
        allows to mark fields as transient with custom annotations/attributes.

        .NET only: Call this method with the attribute name that you wish to use to mark fields as transient. Multiple transient attributes are possible by calling this method multiple times with different attribute names.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Specified by:
        markTransient in interface CommonConfiguration
        Parameters:
        attributeName - - the fully qualified name of the attribute, including it's namespace

      • messageLevel

        public void messageLevel​(int level)
        Description copied from interface: CommonConfiguration
        sets the detail level of db4o messages. Messages will be output to the configured output PrintStream.

        Level 0 - no messages
        Level 1 - open and close messages
        Level 2 - messages for new, update and delete
        Level 3 - messages for activate and deactivate

        When using client-server and the level is set to 0, the server will override this and set it to 1. To get around this you can set the level to -1. This has the effect of not returning any messages.

        In client-server environment this setting can be used on client or on server depending on which information do you want to track (server side provides more detailed information).

        Specified by:
        messageLevel in interface CommonConfiguration
        Parameters:
        level - integer from 0 to 3
        See Also:
        TODO: replace int with enumeration

      • objectClass

        public ObjectClass objectClass​(java.lang.Object clazz)
        Description copied from interface: CommonConfiguration
        returns an ObjectClass object to configure the specified class.

        The clazz parameter can be any of the following:
        - a fully qualified classname as a String.
        - a Class object.
        - any other object to be used as a template.

        Specified by:
        objectClass in interface CommonConfiguration
        Parameters:
        clazz - class name, Class object, or example object.

        Returns:
        an instance of an ObjectClass object for configuration.

      • optimizeNativeQueries

        public void optimizeNativeQueries​(boolean optimizeNQ)
        Description copied from interface: CommonConfiguration
        If set to true, db4o will try to optimize native queries dynamically at query execution time, otherwise it will run native queries in unoptimized mode as SODA evaluations. On the Java platform the jars needed for native query optimization (db4o-X.x-nqopt.jar, bloat-X.x.jar) have to be on the classpath at runtime for this switch to have effect.

        The default setting is true.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Specified by:
        optimizeNativeQueries in interface CommonConfiguration
        Parameters:
        optimizeNQ - true, if db4o should try to optimize native queries at query execution time, false otherwise

      • reflectWith

        public void reflectWith​(Reflector reflector)
        Description copied from interface: CommonConfiguration
        configures the use of a specially designed reflection implementation.

        db4o internally uses java.lang.reflect.* by default. On platforms that do not support this package, customized implementations may be written to supply all the functionality of the interfaces in the com.db4o.reflect package. This method can be used to install a custom reflection implementation.

        In client-server environment this setting should be used on both the client and the server side (reflector class must be available)

        Specified by:
        reflectWith in interface CommonConfiguration

      • outStream

        public void outStream​(java.io.PrintStream outStream)
        Description copied from interface: CommonConfiguration
        Assigns a PrintStream where db4o is to print its event messages.

        Messages are useful for debugging purposes and for learning to understand, how db4o works. The message level can be raised with Configuration.messageLevel(int) to produce more detailed messages.

        Use outStream(System.out) to print messages to the console.

        In client-server environment this setting should be used on the same side where Configuration.messageLevel(int) is used.

        Specified by:
        outStream in interface CommonConfiguration
        Parameters:
        outStream - the new PrintStream for messages.
        See Also:
        CommonConfiguration.messageLevel(int)

      • testConstructors

        public void testConstructors​(boolean flag)
        Description copied from interface: CommonConfiguration
        tuning feature: configures whether db4o should try to instantiate one instance of each persistent class on system startup.

        In a production environment this setting can be set to false, if all persistent classes have public default constructors.

        In a client/server environment it is good practice to configure the client and the server in exactly the same way.

        Default value: true
        Specified by:
        testConstructors in interface CommonConfiguration
        Parameters:
        flag - the desired setting

      • weakReferences

        public void weakReferences​(boolean flag)
        Description copied from interface: CommonConfiguration
        turns weak reference management on or off.

        This method must be called before opening a database.

        Performance may be improved by running db4o without using weak references durring memory management at the cost of higher memory consumption or by alternatively implementing a manual memory management scheme using ExtObjectContainer.purge(java.lang.Object)

        Setting the value to false causes db4o to use hard references to objects, preventing the garbage collection process from disposing of unused objects.

        The default setting is true.
        Specified by:
        weakReferences in interface CommonConfiguration

      • weakReferenceCollectionInterval

        public void weakReferenceCollectionInterval​(int milliseconds)
        Description copied from interface: CommonConfiguration
        configures the timer for WeakReference collection.

        The default setting is 1000 milliseconds.

        Configure this setting to zero to turn WeakReference collection off.
        Specified by:
        weakReferenceCollectionInterval in interface CommonConfiguration
        Parameters:
        milliseconds - the time in milliseconds

      • registerTypeHandler

        public void registerTypeHandler​(TypeHandlerPredicate predicate,
                                TypeHandler4 typeHandler)
        Description copied from interface: CommonConfiguration
        Allows registering special TypeHandlers for customized marshalling and customized comparisons.
        This is only for adventurous people, since type handlers work a the lowest levels:
        • There is no versioning support: If you need to change the serialisation scheme of the type your are on your own.
        • The typehandler-API is mostly undocumented and not as stable as other db4o APIs.
        • Elaborate type handlers need deep knowledge of undocumented, internal implementation details of db4o.
        • Mistakes in typehandlers can lead to cryptic error messages and database corruption.
        Specified by:
        registerTypeHandler in interface CommonConfiguration
        Parameters:
        predicate - to specify for which classes and versions the TypeHandler is to be used.
        typeHandler - to be used for the classes that match the predicate.

      • maxStackDepth

        public void maxStackDepth​(int maxStackDepth)
        Description copied from interface: CommonConfiguration

        Sets the max stack depth that will be used for recursive storing and activating an object.

        The default value is set to Const4.DEFAULT_MAX_STACK_DEPTH

        On Android platform, we recommend setting this to 2.

        Specified by:
        maxStackDepth in interface CommonConfiguration
        Parameters:
        maxStackDepth - the desired max stack depth.