Handler (Java Platform SE 8 )
Keywords: java.util.logging.Handler class
Date: 2015-11-19

compact1, compact2, compact3
java.util.logging

## Class Handler

- java.lang.Object
- - java.util.logging.Handler

- Direct Known Subclasses:
    MemoryHandler, StreamHandler

      public abstract class Handler
      extends Object

  A `Handler` object takes log messages from a `Logger` and exports them. It might for example, write them to a console or write them to a file, or send them to a network logging service, or forward them to an OS log, or whatever.

  A `Handler` can be disabled by doing a `setLevel(Level.OFF)` and can be re-enabled by doing a `setLevel` with an appropriate level.

  `Handler` classes typically use `LogManager` properties to set default values for the `Handler`'s `Filter`, `Formatter`, and `Level`. See the specific documentation for each concrete `Handler` class.

  Since:
    1.4

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `Handler()` Default constructor.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract void` | `close()` Close the `Handler` and free all associated resources.
    `abstract void` | `flush()` Flush any buffered output.
    `String` | `getEncoding()` Return the character encoding for this `Handler`.
    `ErrorManager` | `getErrorManager()` Retrieves the ErrorManager for this Handler.
    `Filter` | `getFilter()` Get the current `Filter` for this `Handler`.
    `Formatter` | `getFormatter()` Return the `Formatter` for this `Handler`.
    `Level` | `getLevel()` Get the log level specifying which messages will be logged by this `Handler`.
    `boolean` | `isLoggable(LogRecord record)` Check if this `Handler` would actually log a given `LogRecord`.
    `abstract void` | `publish(LogRecord record)` Publish a `LogRecord`.
    `protected void` | `reportError(String msg, Exception ex, int code)` Protected convenience method to report an error to this Handler's ErrorManager.
    `void` | `setEncoding(String encoding)` Set the character encoding used by this `Handler`.
    `void` | `setErrorManager(ErrorManager em)` Define an ErrorManager for this Handler.
    `void` | `setFilter(Filter newFilter)` Set a `Filter` to control output on this `Handler`.
    `void` | `setFormatter(Formatter newFormatter)` Set a `Formatter`.
    `void` | `setLevel(Level newLevel)` Set the log level specifying which message levels will be logged by this `Handler`.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### Handler

          protected Handler()

      Default constructor. The resulting `Handler` has a log level of `Level.ALL`, no `Formatter`, and no `Filter`. A default `ErrorManager` instance is installed as the `ErrorManager`.

  - ### Method Detail

    - #### publish

          public abstract void publish(LogRecord record)

      Publish a `LogRecord`.

      The logging request was made initially to a `Logger` object, which initialized the `LogRecord` and forwarded it here.

      The `Handler` is responsible for formatting the message, when and if necessary. The formatting should include localization.

      Parameters:
        `record` - description of the log event. A null record is silently ignored and is not published

    - #### flush

          public abstract void flush()

      Flush any buffered output.

    - #### close

          public abstract void close()
                              throws SecurityException

      Close the `Handler` and free all associated resources.

      The close method will perform a `flush` and then close the `Handler`. After close has been called this `Handler` should no longer be used. Method calls may either be silently ignored or may throw runtime exceptions.

      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### setFormatter

          public void setFormatter(Formatter newFormatter)
                            throws SecurityException

      Set a `Formatter`. This `Formatter` will be used to format `LogRecords` for this `Handler`.

      Some `Handlers` may not use `Formatters`, in which case the `Formatter` will be remembered, but not used.

      Parameters:
        `newFormatter` - the `Formatter` to use (may not be null)
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### getFormatter

          public Formatter getFormatter()

      Return the `Formatter` for this `Handler`.
      Returns:
        the `Formatter` (may be null).

    - #### setEncoding

          public void setEncoding(String encoding)
                           throws SecurityException,
                                  UnsupportedEncodingException

      Set the character encoding used by this `Handler`.

      The encoding should be set before any `LogRecords` are written to the `Handler`.

      Parameters:
        `encoding` - The name of a supported character encoding. May be null, to indicate the default platform encoding.
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.
        `UnsupportedEncodingException` - if the named encoding is not supported.

    - #### getEncoding

          public String getEncoding()

      Return the character encoding for this `Handler`.
      Returns:
        The encoding name. May be null, which indicates the default encoding should be used.

    - #### setFilter

          public void setFilter(Filter newFilter)
                         throws SecurityException

      Set a `Filter` to control output on this `Handler`.

      For each call of `publish` the `Handler` will call this `Filter` (if it is non-null) to check if the `LogRecord` should be published or discarded.

      Parameters:
        `newFilter` - a `Filter` object (may be null)
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### getFilter

          public Filter getFilter()

      Get the current `Filter` for this `Handler`.
      Returns:
        a `Filter` object (may be null)

    - #### setErrorManager

          public void setErrorManager(ErrorManager em)

      Define an ErrorManager for this Handler.

      The ErrorManager's "error" method will be invoked if any errors occur while using this Handler.

      Parameters:
        `em` - the new ErrorManager
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### getErrorManager

          public ErrorManager getErrorManager()

      Retrieves the ErrorManager for this Handler.
      Returns:
        the ErrorManager for this Handler
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### reportError

          protected void reportError(String msg,
                                     Exception ex,
                                     int code)

      Protected convenience method to report an error to this Handler's ErrorManager. Note that this method retrieves and uses the ErrorManager without doing a security check. It can therefore be used in environments where the caller may be non-privileged.
      Parameters:
        `msg` - a descriptive string (may be null)
        `ex` - an exception (may be null)
        `code` - an error code defined in ErrorManager

    - #### setLevel

          public void setLevel(Level newLevel)
                        throws SecurityException

      Set the log level specifying which message levels will be logged by this `Handler`. Message levels lower than this value will be discarded.

      The intention is to allow developers to turn on voluminous logging, but to limit the messages that are sent to certain `Handlers`.

      Parameters:
        `newLevel` - the new value for the log level
      Throws:
        `SecurityException` - if a security manager exists and if the caller does not have `LoggingPermission("control")`.

    - #### getLevel

          public Level getLevel()

      Get the log level specifying which messages will be logged by this `Handler`. Message levels lower than this level will be discarded.
      Returns:
        the level of messages being logged.

    - #### isLoggable

          public boolean isLoggable(LogRecord record)

      Check if this `Handler` would actually log a given `LogRecord`.

      This method checks if the `LogRecord` has an appropriate `Level` and whether it satisfies any `Filter`. It also may make other `Handler` specific checks that might prevent a handler from logging the `LogRecord`. It will return false if the `LogRecord` is null.

      Parameters:
        `record` - a `LogRecord`
      Returns:
        true if the `LogRecord` would be logged.

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