JRas programming interfaces for logging (deprecated)

 

The JRas framework described in this task and its sub-tasks is deprecated. However, you can achieve similar results using Java logging.

 

General considerations

You can configure the WebSphere Application Server to use Java 2 security to restrict access to protected resources such as the file system and sockets. Because user-written extensions typically access such protected resources, user-written extensions must contain the appropriate security checking calls, using AccessController doPrivileged calls. In addition, the user-written extensions must contain the appropriate policy file. In general, locating user-written extensions in a separate package is a good practice. It is your responsibility to restrict access to the user-written extensions appropriately.

 

Writing a handler

User-written handlers must implement the RASIHandler interface. The RASIHandler interface extends the RASIMaskChangeGenerator interface, which extends the RASIObject interface. A short discussion of the methods that are introduced by each of these interfaces follows, along with implementation pointers. For more in-depth information on any of the particular interfaces or methods, see the corresponding product API documentation.

 

RASIObject interface

The RASIObject interface is the base interface for stand-alone JRas logging toolkit classes that are stateful or configurable, such as loggers, handlers, and formatters.

• The stand-alone JRas logging tookit supports rudimentary properties-file based configuration. To implement this configuration support, the configuration state is stored as a set of key-value pairs in a properties file. The public Hashtable getConfig and public void setConfig(Hashtable ht) methods are used to get and set the configuration state. The JRas extensions do not support properties-based configuration. Implement these methods as no-operations. You can implement your own properties-based configuration using these methods.

• Loggers, handlers, and formatters can be named objects. For example, the JRas extensions require the user to provide a name for the loggers that are retrieved from the manager. You can name your handlers. The public String getName and public void setName(String name) methods are provided to get or set the name field. The JRas extensions currently do not call these methods on user handlers. You can implement these methods as you want, including as no operations.

• Loggers, handlers, and formatters can also contain a description field. The public String getDescription and public void setDescription(String desc) methods can be used to get or set the description field. The JRas extensions currently do not use the description field. You can implement these methods as you want, including as no operations.

• The public String getGroup method is provided for use by the RASManager interface. Since the JRas extensions provide their own Manager class, this method is never called. Implement this as a no-operation.

 

RASIMaskChangeGenerator interface

The RASIMaskChangeGenerator interface is the interface that defines the implementation methods for filtering of events based on a mask state. It is currently implemented by both loggers and handlers. By definition, an object that implements this interface contains both a message mask and a trace mask, although both need not be used. For example, message loggers contain a trace mask, but the trace mask is never used because the message logger never generates trace events. Handlers, however, can actively use both mask values. For example, a single handler can handle both message and trace events.

• The public long getMessageMask and public void setMessageMask(long mask) methods are used to get or set the value of the message mask. The public long getTraceMask and public void setTraceMask(long mask) methods are used to get or set the value of the trace mask.

In addition, this interface introduces the concept of calling back to interested parties when a mask changes state. The callback object must implement the RASIMaskChangeListener interface.

• The public void addMaskChangeListener(RASIMaskChangeListener listener) and public void removeMaskChangeListener(RASIMaskChangeListener listener) methods are used to add or remove listeners to the handler. The public Enumeration getMaskChangeListeners method returns an enumeration over the list of currently registered listeners. The public void fireMaskChangedEvent(RASMaskChangeEvent mc) method is used to call back all the registered listeners to inform them of a mask change event.

For efficiency reasons, the JRas extensions message and trace loggers implement the RASIMaskChangeListener interface. The logger implementations maintain a composite mask in addition to the logger mask. The logger composite mask is formed by logically or'ing the appropriate masks of all handlers that are registered to that logger, then and'ing the result with the logger mask. For example, the message logger composite mask is formed by or'ing the message masks of all handlers that are registered with that logger, then and'ing the result with the logger message mask.

All handlers are required to properly implement these methods. In addition, when a user handler is instantiated, the logger that is added must be registered with the handler; use the addMaskChangeListener method. When either the message mask or trace mask of the handler is changed, the logger must be called back to inform it of the mask change. With this process, the logger can dynamically maintain the composite mask.

The RASMaskChangedEvent class is defined by the stand-alone JRas logging toolkit. Direct use of that class by user code is supported in this context.

In addition, the RASIMaskChangeGenerator interface introduces the concept of caching the names of all message and trace event classes that the implementing object process. The intent of these methods is to support a management program such as a graphical user interface to retrieve the list of names, introspect the classes to determine the event types that they might possibly process and display the results. The JRas extensions do not ever call these methods, so they can be implemented as no operations.

• The public void addMessageEventClass(String name) and public void removeMessageEventClass(String name) methodscan be called to add or remove a message event class name from the list. The method public Enumeration getMessageEventClasses returns an enumeration over the list of message event class names. Similarly, the public void addTraceEventClass(String name) and public void removeTraceEventClass(String name) methods can be called to add or remove a trace event class name from the list. The public Enumeration getTraceEventClasses method returns an enumeration over the list of trace event class names.

 

RASIHandler interface

The RASIHandler interface introduces the methods that are specific to the behavior of a handler.

The RASIHandler interface, as provided by the stand-alone JRas logging toolkit, supports handlers that run in either a synchronous or asynchronous mode. In asynchronous mode, events are typically queued by the calling thread and then written by a worker thread. Because spawning of threads is not supported in the WAS environment, it is expected that handlers do not queue or batch events, although this activity is not expressly prohibited.

• The public int getMaximumQueueSize() and public void setMaximumQueueSize(int size) methods create IllegalStateException exceptions to manage the maximum queue size. The public int getQueueSize method is provided to query the actual queue size.

• The public int getRetryInterval and public void setRetryInterval(int interval) methods support the notion of error retry, which implies some type of queueing.

• The public void addFormatter(RASIFormatter formatter), public void removeFormatter(RASIFormatter formatter) and public Enumeration getFormatters methods are provided to manage the list of formatters that the handler can be configured with. Different formatters can be provided for different event classes, if appropriate.

• The public void openDevice, public void closeDevice and public void stop methods are provided to manage the underlying device that the handler abstracts.

• The public void logEvent(RASIEvent event) and public void writeEvent(RASIEvent event) methods are provided to pass events to the handler for processing.

 

Writing a formatter

User-written formatters must implement the RASIFormatter interface. The RASIFormatter interface extends the RASIObject interface. The implementation of the RASIObject interface is the same for both handlers and formatters. A short discussion of the methods that are introduced by the RASIFormatter interface follows. For more in-depth information on the methods introduced by this interface, see the corresponding product API documentation.

 

RASIFormatter interface

• The public void setDefault(boolean flag) and public boolean isDefault methods are used by the concrete RASHandler classes that are provided by the stand-alone JRas logging toolkit to determine if a particular formatter is the default formatter. Because these RASHandler classes must never be used in a WAS environment, the semantic significance of these methods can be determined by the user.

• The public void addEventClass(String name), public void removeEventClass(String name) and public Enumeration getEventClasses methods are provided to determine which event classes a formatter can use to format. You can provide the appropriate implementations.

• The public String format(RASIEvent event) method is called by handler objects and returns a formatted String representation of the event.

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Related concepts

JRas framework (deprecated)

 

Related tasks

Programming with the JRas framework

 

Related Reference

JRas Extensions

 

Reference topic