WarningListeners (Apache SIS 0.8 API)

Object
- WarningListeners<S>

Type Parameters:

S - the type of the source of warnings.

All Implemented Interfaces:

Localized
```
public class WarningListeners<S>
extends Object
implements Localized
```
Holds a list of WarningListener instances and provides convenience methods for emitting warnings. This is a helper class for DataStore implementations or for other services susceptible to emit warnings. Observers can can add listeners for being notified about warnings, and processes can invoke one of the warning(…) methods for emitting warnings. All warnings are given to the listeners as LogRecord instances (this allows localizable messages and additional information like timestamp and stack trace). This WarningListeners class provides convenience methods like warning(String, Exception), which builds LogRecord from an exception or from a string, but all those warning(…) methods ultimately delegate to warning(LogRecord), thus providing a single point that subclasses can override. When a warning is emitted, the default behavior is:
- If at least one WarningListener is registered, then all listeners are notified and the warning is not logged.
- Otherwise if the value returned by LogRecord.getLoggerName() is non-null, then the warning will be logged to that named logger.
- Otherwise the warning is logged to the logger returned by getLogger().
Thread safety
The same WarningListeners instance can be safely used by many threads without synchronization on the part of the caller. Subclasses should make sure that any overridden methods remain safe to call from multiple threads.
Since:

0.3

See Also:

WarningListener, DataStore.listeners

Defined in the sis-utility module

Constructor Summary

Constructors
Constructor and Description
`WarningListeners(S source)` Creates a new instance with initially no listener.
`WarningListeners(S source, WarningListeners<? super S> other)` Creates a new instance initialized with the same listeners than the given instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addWarningListener(WarningListener<? super S> listener)` Adds a listener to be notified when a warning occurred.
`List<WarningListener<? super S>>`	`getListeners()` Returns all registered warning listeners, or an empty list if none.
`Locale`	`getLocale()` The locale to use for formatting warning messages, or `null` for the default locale.
`Logger`	`getLogger()` Returns the logger where to send the warnings when no other destination is specified.
`S`	`getSource()` Returns the source declared source of warnings.
`boolean`	`hasListeners()` Returns `true` if this object contains at least one listener.
`void`	`removeWarningListener(WarningListener<? super S> listener)` Removes a previously registered listener.
`void`	`warning(Level level, String message, Exception exception)` Reports a warning at the given level represented by the given message and exception.
`void`	`warning(LogRecord record)` Reports a warning represented by the given log record.
`void`	`warning(String message, Exception exception)` Reports a warning represented by the given message and exception.

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - WarningListeners
```
public WarningListeners(S source)
```
    Creates a new instance with initially no listener. Warnings will be logger to the destination given by getLogger(), unless at least one listener is registered.
    
    Parameters:
    
    source - the declared source of warnings. This is not necessarily the real source, but this is the source that the implementor wants to declare as public API.
  - WarningListeners
```
public WarningListeners(S source,
                        WarningListeners<? super S> other)
```
    Creates a new instance initialized with the same listeners than the given instance. This constructor is useful when a DataStore or other data producer needs to be duplicated for concurrency reasons.
    
    Parameters:
    
    source - the declared source of warnings. This is not necessarily the real source, but this is the source that the implementor wants to declare as public API.
    
    other - the existing instance from which to copy the listeners, or null if none.
    
    Since:
    
    0.8
- Method Detail
  - getSource
```
public S getSource()
```
    Returns the source declared source of warnings. This value is specified at construction time.
    
    Returns:
    
    the declared source of warnings.
    
    Since:
    
    0.8
  - getLocale
```
public Locale getLocale()
```
    The locale to use for formatting warning messages, or null for the default locale. If the source object given to the constructor implements the Localized interface, then this method delegates to its getLocale() method. Otherwise this method returns null.
    
    Specified by:
    
    getLocale in interface Localized
    
    Returns:
    
    the locale, or null if not explicitly defined.
  - getLogger
```
public Logger getLogger()
```
    Returns the logger where to send the warnings when no other destination is specified. This logger is used when:
    - no listener has been registered, and
    - the LogRecord does not specify a logger.
    The default implementation infers a logger name from the package name of the source object. Subclasses should override this method if they can provide a more determinist logger instance, typically from a static final constant.
    Returns:
    
    the logger where to send the warnings when there is no other destination.
  - warning
```
public void warning(LogRecord record)
```
    Reports a warning represented by the given log record. The default implementation forwards the given record to one of the following destinations, in preference order:
    1. WarningListener.warningOccured(source, record) on all registered listeners it at least one such listener exists.
    2. Logging.getLogger(record.getLoggerName()).log(record) if the logger name is non-null.
    3. getLogger().log(record) otherwise.
    Parameters:
    
    record - the warning as a log record.
  - warning
```
public void warning(String message,
                    Exception exception)
```
    Reports a warning represented by the given message and exception. At least one of message and exception shall be non-null. If both are non-null, then the exception message will be concatenated after the given message. If the exception is non-null, its stack trace will be omitted at logging time for avoiding to pollute console output (keeping in mind that this method should be invoked only for non-fatal warnings). See below for more explanation.
    This method is a shortcut for warning(Level.WARNING, message, exception).
    
    Parameters:
    
    message - the message to log, or null if none.
    
    exception - the exception to log, or null if none.
  - warning
```
public void warning(Level level,
                    String message,
                    Exception exception)
```
    Reports a warning at the given level represented by the given message and exception. At least one of message and exception shall be non-null. If both are non-null, then the exception message will be concatenated after the given message.
    Stack trace omission
    If there is no registered listener, then the warning(LogRecord) method will send the record to the logger, but without the stack trace. This is done that way because stack traces consume lot of space in the logging files, while being considered implementation details in the context of WarningListeners (on the assumption that the logging message provides sufficient information). If the stack trace is desired, then users can either:
    - invoke warning(LogRecord) directly, or
    - override warning(LogRecord) and invoke LogRecord.setThrown(Throwable) explicitely, or
    - register a listener which will log the record itself.
    Parameters:
    
    level - the warning level.
    
    message - the message to log, or null if none.
    
    exception - the exception to log, or null if none.
  - addWarningListener
```
public void addWarningListener(WarningListener<? super S> listener)
                        throws IllegalArgumentException
```
    Adds a listener to be notified when a warning occurred. When a warning occurs, there is a choice:
    - If this object has no warning listener, then the warning is logged at Level.WARNING.
    - If this object has at least one warning listener, then all listeners are notified and the warning is not logged by this object.
    Parameters:
    
    listener - the listener to add.
    
    Throws:
    
    IllegalArgumentException - if the given listener is already registered.
  - removeWarningListener
```
public void removeWarningListener(WarningListener<? super S> listener)
                           throws NoSuchElementException
```
    Removes a previously registered listener.
    
    Parameters:
    
    listener - the listener to remove.
    
    Throws:
    
    NoSuchElementException - if the given listener is not registered.
  - getListeners
```
public List<WarningListener<? super S>> getListeners()
```
    Returns all registered warning listeners, or an empty list if none. This method returns an unmodifiable snapshot of the listener list at the time this method is invoked.
    
    Returns:
    
    immutable list of all registered warning listeners.
    
    Since:
    
    0.8
  - hasListeners
```
public boolean hasListeners()
```
    Returns true if this object contains at least one listener.
    
    Returns:
    
    true if this object contains at least one listener, false otherwise.
    
    Since:
    
    0.4

Class WarningListeners<S>

Constructor Summary

Method Summary

Methods inherited from class Object

Constructor Detail

WarningListeners

WarningListeners

Method Detail

getSource

getLocale

getLogger

warning

warning

warning

addWarningListener

removeWarningListener

getListeners

hasListeners