org.apache.commons.configuration2.sync

## Interface Synchronizer

- All Known Implementing Classes:
    NoOpSynchronizer, ReadWriteSynchronizer

      public interface Synchronizer

  An interface controlling synchronization of configuration instances.

  Each `Configuration` object derived from `AbstractConfiguration` has an associated `Synchronizer` object. Before an operation on the configuration is performed (e.g. a property read or an update), the `Synchronizer` is invoked. Depending on the concrete implementation of the `Synchronizer` used, the configuration can be made thread-safe.

  Whether a configuration has to be thread-safe or not is a matter of a concrete use case. For instance, an application that just reads some configuration settings on startup does need a thread-safe configuration implementation. A configuration in contrast which is shared between multiple components and updated concurrently should better be thread-safe. In order to satisfy both kinds of use cases, the support for thread-safety has been extracted out of the configuration implementation and refactored into this `Synchronizer` interface. By assigning different `Synchronizer` implementations to a configuration instance, the instance's support for concurrent access can be adapted to the concrete use case.

  The methods defined by this interface are similar to a read-write lock. The `Synchronizer` is notified when read or write operations start and end. A concrete implementation can then apply a specific policy to decide when threads need to block or when access to the configuration for the desired operation is granted.

  Since:
    2.0
  Version:
    $Id: Synchronizer.java 1678634 2015-05-10 20:21:39Z oheger $

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `beginRead()` Notifies this `Synchronizer` that the current thread is going to start a read operation on the managed configuration.
    `void` | `beginWrite()` Notifies this `Synchronizer` that the current thread is going to start a write operation on the managed configuration.
    `void` | `endRead()` Notifies this `Synchronizer` that the current thread has finished its read operation.
    `void` | `endWrite()` Notifies this `Synchronizer` that the current thread has finished its write operation.

- - ### Method Detail

    - #### beginRead

          void beginRead()

      Notifies this `Synchronizer` that the current thread is going to start a read operation on the managed configuration. This call can block if a concrete implementation decides that the thread has to wait until a specific condition is fulfilled.

    - #### endRead

          void endRead()

      Notifies this `Synchronizer` that the current thread has finished its read operation. This may cause other waiting threads to be granted access to the managed configuration.

    - #### beginWrite

          void beginWrite()

      Notifies this `Synchronizer` that the current thread is going to start a write operation on the managed configuration. This call may block. For instance, a concrete implementation may suspend the thread until all read operations currently active are finished,

    - #### endWrite

          void endWrite()

      Notifies this `Synchronizer` that the current thread has finished its write operation. This may cause other waiting threads to be granted access to the managed configuration.

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