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Interim replacement for JSR 77 Stats and Statistics

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Provides for implementations of various Stats interfaces. These Stats interfaces
are based on those defined by JSR 77. Besides this, implementations of
various Statistic interfaces are also provided here. A new Statistic is
introduced named  StringStatistic .

When we analyze the Statistic interfaces that are defined by the J2EE Management
Standard, it is evident that they are view-only data structures providing the
accessors for various statistical data, e.g. CountStatistic. Every instance of
CountStatistic is allowed to have only a  getCount  method (in
addition to other meta data accessors), that returns a long. This limits the
usability of these Statistic interfaces by the actual components that gather the
data, because new instances of these interfaces have to be constructed as
and when a query or measurement of that statistic is made. On the other hand, it
is much more flexible to have mutators within implementations of these Statistic
interfaces. But then, there is a possibility that the client who receives
instances of these interfaces inadvertantly changes a particular statistic.

To solve this problem, this package makes the following provision:

It defines Statistic classes that have a State. A component that gathers
data has to do the following:

    
   Implement the specific Stats interface. e.g. EJBCacheStats. This interface 
    has a method which returns number of beans in cache as an instance of BoundedRangeStatistic. 
  
    
   Initialize an instance of MutableBoundedRangeStatistic with an initial 
    state. This interface exposes all the necessary methods that are required 
    to reflect the change in state. 
    
   Since MutableBoundedRangeStatistic provides a method that returns an unmodifiable 
    view of itself, calls the MutableBoundedRangeStatistic.unmodifiableView() 
    which returns BoundedRangeStatistic. This returned value can safely be sent 
    to the caller to which everything is transparent.


Note that these Mutable* interfaces/classes are not exposed to clients. Clients 
will only receive instances of Statistics that are part of the J2EE Management 
Standard. 
Package Specification
Following Stats interfaces are part of this package. All of these extend the
org.glassfish.j2ee.statistics.Stats interface.

  EJBCacheStats
  EJBMethodStats
  EJBPoolStats
  OrbConnectionManagerStats
  OrbThreadPoolStats
  SunOneJVMStats


Following new Statistic interfaces are defined by this package. They extend the 
org.glassfish.j2ee.statistics.Statististic interface. 

  StringStatistic - A String equivalent of CountStatistic.
  MutableStatistic - A Statistic that has some mutators. It is expected to 
    be handled with care.
  MutableCountStatistic - A CountStatistic/BoundedRangeStatistic that is mutable.
  MutableTimeStatistic - A TimeStatistic that is mutable.

Following are the implementations of various Statistic interfaces in org.glassfish.j2ee.statistics 
  package.

   
    Interface
    Immutable Implementation (read-only -- for clients)
    Mutable Implementation (read-write -- for core components)
  
   
    CountStatistic
    CountStatisticImpl
    MutableCountStatisticImpl

      It implements MutableCountStatistic.
  
   
    BoundedRangeStatistic
    BoundedRangeStatisticImpl
    MutableBoundedRangeStatisticImpl

      It implements MutableCountStatistic.
  
  
    TimeStatistic
    TimeStatisticImpl
    MutableTimeStatisticImpl

      It implements MutableTimeStatistic.
  

  

Following is a helper implementation done in this package: GenericStatsImpl.

This class is designed to facilitate the general implementation of {@link
Stats} interface and all the classes that implement this interface can leverage
this class. The main idea is that this class implements:

    getStatistic(String)
    getStatistics()
    getStatisticNames()

in a reflective manner. Thus, e.g. a specific implementation of EJBPoolStats like
EJBPoolStatsImpl can make use of this class to implement above methods in a
generic manner.
Related Documentation

{@link org.glassfish.j2ee.statistics}

  {@link java.util.Collections#unmodifiableMap}

  {@link java.util.Collections#unmodifiableSet}


@since S1AS8.0

Interface	Immutable Implementation (read-only -- for clients)	Mutable Implementation (read-write -- for core components)
CountStatistic	CountStatisticImpl	MutableCountStatisticImpl It implements MutableCountStatistic.
BoundedRangeStatistic	BoundedRangeStatisticImpl	MutableBoundedRangeStatisticImpl It implements MutableCountStatistic.
TimeStatistic	TimeStatisticImpl	MutableTimeStatisticImpl It implements MutableTimeStatistic.