XMLFormatter (Java SE 25 & JDK 25)
Description: declaration: module: java.logging, package: java.util.logging, class: XMLFormatter
Keywords: java.util.logging.XMLFormatter class

# 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

  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 Formatter

  `formatMessage`

  ### Methods declared in class Object

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

- ## Constructor Details

  - ### 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 Details

  - ### 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(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