Module java.logging
Package java.util.logging

## Class XMLFormatter

- java.lang.Object
- - java.util.logging.Formatter
  - - java.util.logging.XMLFormatter

-     public class XMLFormatter
      extends Formatter

  Format a LogRecord into a standard XML format.

  The DTD specification is provided as Appendix A to the Java Logging APIs specification.

  The XMLFormatter can be used with arbitrary character encodings, but it is recommended that it normally be used with UTF-8. The character encoding can be set on the output Handler.

  Implementation Requirements:
    Since JDK 9, instances of LogRecord contain an `Instant` which can have nanoseconds below the millisecond resolution. The DTD specification has been updated to allow for an optional `<nanos>` element. By default, the XMLFormatter will compute the nanosecond adjustment below the millisecond resolution (using `LogRecord.getInstant().getNano() % 1000_000`) - and if this is not 0, this adjustment value will be printed in the new `<nanos>` element. The event instant can then be reconstructed using `Instant.ofEpochSecond(millis/1000L, (millis % 1000L) * 1000_000L + nanos)` where `millis` and `nanos` represent the numbers serialized in the `<millis>` and `<nanos>` elements, respectively.
    The `<date>` element will now contain the whole instant as formatted by the `DateTimeFormatter.ISO_INSTANT` formatter.

    For compatibility with old parsers, XMLFormatters can be configured to revert to the old format by specifying a `<xml-formatter-fully-qualified-class-name>.useInstant = false` property in the logging configuration. When `useInstant` is `false`, the old formatting will be preserved. When `useInstant` is `true` (the default), the `<nanos>` element will be printed and the `<date>` element will contain the formatted instant.

    For instance, in order to configure plain instances of XMLFormatter to omit the new `<nano>` element, `java.util.logging.XMLFormatter.useInstant = false` can be specified in the logging configuration.

  Since:
    1.4

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `XMLFormatter()` | Creates a new instance of XMLFormatter.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `String` | `format​(LogRecord record)` | Format the given message to XML.
    `String` | `getHead​(Handler h)` | Return the header string for a set of XML formatted records.
    `String` | `getTail​(Handler h)` | Return the tail string for a set of XML formatted records.

    - ### Methods declared in class java.util.logging.Formatter

      `formatMessage`

    - ### Methods declared in class java.lang.Object

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

- - ### Constructor Detail

    - #### XMLFormatter

          public XMLFormatter()

      Creates a new instance of XMLFormatter.
      Implementation Requirements:
        Since JDK 9, the XMLFormatter will print out the record event time as an Instant. This instant has the best resolution available on the system. The `<date>` element will contain the instant as formatted by the `DateTimeFormatter.ISO_INSTANT`. In addition, an optional `<nanos>` element containing a nanosecond adjustment will be printed if the instant contains some nanoseconds below the millisecond resolution.

        This new behavior can be turned off, and the old formatting restored, by specifying a property in the logging configuration. If `LogManager.getLogManager().getProperty( this.getClass().getName()+".useInstant")` is `"false"` or `"0"`, the old formatting will be restored.

  - ### Method Detail

    - #### format

          public String format​(LogRecord record)

      Format the given message to XML.

      This method can be overridden in a subclass. It is recommended to use the `Formatter.formatMessage(java.util.logging.LogRecord)` convenience method to localize and format the message field.

      Specified by:
        `format` in class `Formatter`
      Parameters:
        `record` - the log record to be formatted.
      Returns:
        a formatted log record

    - #### getHead

          public String getHead​(Handler h)

      Return the header string for a set of XML formatted records.
      Overrides:
        `getHead` in class `Formatter`
      Parameters:
        `h` - The target handler (can be null)
      Returns:
        a valid XML string

    - #### getTail

          public String getTail​(Handler h)

      Return the tail string for a set of XML formatted records.
      Overrides:
        `getTail` in class `Formatter`
      Parameters:
        `h` - The target handler (can be null)
      Returns:
        a valid XML string