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| Provides for <b>implementations of various Stats interfaces.</b> 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 <b> StringStatistic </b>. |
| <P> |
| 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 <EM> getCount </EM> 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. |
| <P> |
| To solve this problem, this package makes the following provision: |
| <P> |
| It defines Statistic classes that have a <i>State</i>. A component that gathers |
| data has to do the following: |
| <ul> |
| |
| <li> 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. |
| </li> |
| |
| <li> 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. </li> |
| |
| <li> 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.</li> |
| </ul> |
| |
| 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. |
| <h2>Package Specification</h2> |
| Following Stats interfaces are part of this package. All of these extend the |
| org.glassfish.j2ee.statistics.Stats interface. |
| <ul> |
| <li>EJBCacheStats</li> |
| <li>EJBMethodStats</li> |
| <li>EJBPoolStats</li> |
| <li>OrbConnectionManagerStats</li> |
| <li>OrbThreadPoolStats</li> |
| <li>SunOneJVMStats</li> |
| </ul> |
| |
| Following new Statistic interfaces are defined by this package. They extend the |
| org.glassfish.j2ee.statistics.Statististic interface. |
| <ul> |
| <li>StringStatistic - A String equivalent of CountStatistic.</li> |
| <li>MutableStatistic - A Statistic that has some mutators. It is expected to |
| be handled with care.</li> |
| <li>MutableCountStatistic - A CountStatistic/BoundedRangeStatistic that is mutable.</li> |
| <li>MutableTimeStatistic - A TimeStatistic that is mutable.</li> |
| </ul> |
| <p>Following are the implementations of various Statistic interfaces in org.glassfish.j2ee.statistics |
| package.</p> |
| <table width="60%" border="1"> |
| <tr bgcolor="#0066FF"> |
| <td>Interface</td> |
| <td>Immutable Implementation (read-only -- for clients)</td> |
| <td>Mutable Implementation (read-write -- for core components)</td> |
| </tr> |
| <tr> |
| <td>CountStatistic</td> |
| <td>CountStatisticImpl</td> |
| <td>MutableCountStatisticImpl<br> |
| It implements MutableCountStatistic.</td> |
| </tr> |
| <tr> |
| <td>BoundedRangeStatistic</td> |
| <td>BoundedRangeStatisticImpl</td> |
| <td>MutableBoundedRangeStatisticImpl<br> |
| It implements MutableCountStatistic.</td> |
| </tr> |
| <tr> |
| <td>TimeStatistic</td> |
| <td>TimeStatisticImpl</td> |
| <td>MutableTimeStatisticImpl<br> |
| It implements MutableTimeStatistic.</td> |
| </tr> |
| </table> |
| <p> </p> |
| |
| Following is a helper implementation done in this package: GenericStatsImpl. |
| <p> |
| 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: |
| <ul> |
| <li>getStatistic(String)</li> |
| <li>getStatistics()</li> |
| <li>getStatisticNames()</li> |
| </ul> |
| 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. |
| <h2>Related Documentation</h2> |
| |
| <p>{@link org.glassfish.j2ee.statistics}<br> |
| {@link java.util.Collections#unmodifiableMap}<br> |
| {@link java.util.Collections#unmodifiableSet}<br> |
| </p> |
| <p>@since S1AS8.0 </p> |
| </body> |
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