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## org.apache.log4j
Class AppenderSkeleton

    java.lang.Object
      |
      +--org.apache.log4j.AppenderSkeleton

All Implemented Interfaces:
  Appender, OptionHandler

Direct Known Subclasses:
  AsyncAppender, JDBCAppender, JMSAppender, LF5Appender, NTEventLogAppender, NullAppender, NullAppender, SMTPAppender, SocketAppender, SocketHubAppender, SyslogAppender, TelnetAppender, WriterAppender

public abstract class AppenderSkeleton
extends Object
implements Appender, OptionHandler

Abstract superclass of the other appenders in the package. This class provides the code for common functionality, such as support for threshold filtering and support for general filters.

Since:
  0.8.1
Author:
  Ceki Gülcü

Field Summary
`protected boolean` | `closed` Is this appender closed?
`protected ErrorHandler` | `errorHandler` It is assumed and enforced that errorHandler is never null.
`protected Filter` | `headFilter` The first filter in the filter chain.
`protected Layout` | `layout` The layout variable does not need to be set if the appender implementation has its own layout.
`protected String` | `name` Appenders are named.
`protected Filter` | `tailFilter` The last filter in the filter chain.
`protected Priority` | `threshold` There is no level threshold filtering by default.

Constructor Summary
`AppenderSkeleton()`

Method Summary
`void` | `activateOptions()` Derived appenders should override this method if option structure requires it.
`void` | `addFilter(Filter newFilter)` Add a filter to end of the filter list.
`protected abstract void` | `append(LoggingEvent event)` Subclasses of `AppenderSkeleton` should implement this method to perform actual logging.
`void` | `clearFilters()` Clear the filters chain.
`void` | `doAppend(LoggingEvent event)` This method performs threshold checks and invokes filters before delegating actual logging to the subclasses specific `append(org.apache.log4j.spi.LoggingEvent)` method.
`void` | `finalize()` Finalize this appender by calling the derived class' `close` method.
`ErrorHandler` | `getErrorHandler()` Return the currently set `ErrorHandler` for this Appender.
`Filter` | `getFilter()` Returns the head Filter.
`Filter` | `getFirstFilter()` Return the first filter in the filter chain for this Appender.
`Layout` | `getLayout()` Returns the layout of this appender.
`String` | `getName()` Returns the name of this FileAppender.
`Priority` | `getThreshold()` Returns this appenders threshold level.
`boolean` | `isAsSevereAsThreshold(Priority priority)` Check whether the message level is below the appender's threshold.
`void` | `setErrorHandler(ErrorHandler eh)` Set the `ErrorHandler` for this Appender.
`void` | `setLayout(Layout layout)` Set the layout for this appender.
`void` | `setName(String name)` Set the name of this Appender.
`void` | `setThreshold(Priority threshold)` Set the threshold level.

Methods inherited from class java.lang.Object
`clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface org.apache.log4j.Appender
`close, requiresLayout`

Field Detail

### layout

    protected Layout layout

  The layout variable does not need to be set if the appender implementation has its own layout.

### name

    protected String name

  Appenders are named.

### threshold

    protected Priority threshold

  There is no level threshold filtering by default.

### errorHandler

    protected ErrorHandler errorHandler

  It is assumed and enforced that errorHandler is never null.

### headFilter

    protected Filter headFilter

  The first filter in the filter chain. Set to `null` initially.

### tailFilter

    protected Filter tailFilter

  The last filter in the filter chain.

### closed

    protected boolean closed

  Is this appender closed?

Constructor Detail

### AppenderSkeleton

    public AppenderSkeleton()

Method Detail

### activateOptions

    public void activateOptions()

  Derived appenders should override this method if option structure requires it.
  Specified by:
    `activateOptions` in interface `OptionHandler`

### addFilter

    public void addFilter(Filter newFilter)

  Add a filter to end of the filter list.
  Specified by:
    `addFilter` in interface `Appender`
  Since:
    0.9.0

### append

    protected abstract void append(LoggingEvent event)

  Subclasses of `AppenderSkeleton` should implement this method to perform actual logging. See also `AppenderSkeleton.doAppend` method.
  Since:
    0.9.0

### clearFilters

    public void clearFilters()

  Clear the filters chain.
  Specified by:
    `clearFilters` in interface `Appender`
  Since:
    0.9.0

### finalize

    public void finalize()

  Finalize this appender by calling the derived class' `close` method.
  Overrides:
    `finalize` in class `Object`
  Since:
    0.8.4

### getErrorHandler

    public ErrorHandler getErrorHandler()

  Return the currently set `ErrorHandler` for this Appender.
  Specified by:
    `getErrorHandler` in interface `Appender`
  Since:
    0.9.0

### getFilter

    public Filter getFilter()

  Returns the head Filter.
  Specified by:
    `getFilter` in interface `Appender`
  Since:
    1.1

### getFirstFilter

    public final Filter getFirstFilter()

  Return the first filter in the filter chain for this Appender. The return value may be `null` if no is filter is set.

### getLayout

    public Layout getLayout()

  Returns the layout of this appender. The value may be null.
  Specified by:
    `getLayout` in interface `Appender`

### getName

    public final String getName()

  Returns the name of this FileAppender.
  Specified by:
    `getName` in interface `Appender`

### getThreshold

    public Priority getThreshold()

  Returns this appenders threshold level. See the `setThreshold(org.apache.log4j.Priority)` method for the meaning of this option.
  Since:
    1.1

### isAsSevereAsThreshold

    public boolean isAsSevereAsThreshold(Priority priority)

  Check whether the message level is below the appender's threshold. If there is no threshold set, then the return value is always `true`.

### doAppend

    public void doAppend(LoggingEvent event)

  This method performs threshold checks and invokes filters before delegating actual logging to the subclasses specific `append(org.apache.log4j.spi.LoggingEvent)` method.
  Specified by:
    `doAppend` in interface `Appender`

### setErrorHandler

    public void setErrorHandler(ErrorHandler eh)

  Set the `ErrorHandler` for this Appender.
  Specified by:
    `setErrorHandler` in interface `Appender`
  Since:
    0.9.0

### setLayout

    public void setLayout(Layout layout)

  Set the layout for this appender. Note that some appenders have their own (fixed) layouts or do not use one. For example, the `SocketAppender` ignores the layout set here.
  Specified by:
    `setLayout` in interface `Appender`

### setName

    public void setName(String name)

  Set the name of this Appender.
  Specified by:
    `setName` in interface `Appender`

### setThreshold

    public void setThreshold(Priority threshold)

  Set the threshold level. All log events with lower level than the threshold level are ignored by the appender.

  In configuration files this option is specified by setting the value of the Threshold option to a level string, such as "DEBUG", "INFO" and so on.

  Since:
    0.8.3

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