private static String logWithSpanAndLog4jConfiguration(
    String log4jPattern, SpanContext spanContext, Function<Logger, Void> loggingFunction) {
  StringWriter output = new StringWriter();
  StringLayout layout = PatternLayout.newBuilder().withPattern(log4jPattern).build();
  Appender appender =
      WriterAppender.newBuilder()
          .setTarget(output)
          .setLayout(layout)
          .setName("TestAppender")
          .build();
  ((LoggerContext) LogManager.getContext(false)).updateLoggers();
  appender.start();
  logger.addAppender(appender);
  logger.setLevel(Level.ALL);
  try {
    logWithSpan(spanContext, loggingFunction, logger);
    return output.toString();
  } finally {
    logger.removeAppender(appender);
  }
}
 

@Override
public void append(LogEvent event) {
  readLock.lock();
  try {
    if (textArea == null) {
      // just ignore any events logged before the area is available
      return;
    }

    final String message = ((StringLayout) getLayout()).toSerializable(event);
    SwingUtilities.invokeLater(() -> {
      textArea.append(message);
    });
  } finally {
    readLock.unlock();
  }
}
 

public WriterManager(final Writer writer, final String streamName, final StringLayout layout,
        final boolean writeHeader) {
    super(null, streamName);
    this.writer = writer;
    this.layout = layout;
    if (writeHeader && layout != null) {
        final byte[] header = layout.getHeader();
        if (header != null) {
            try {
                this.writer.write(new String(header, layout.getCharset()));
            } catch (final IOException e) {
                logError("Unable to write header", e);
            }
        }
    }
}
 

@Override
public WriterAppender build() {
    final StringLayout layout = (StringLayout) getLayout();
    final StringLayout actualLayout = layout != null ? layout : PatternLayout.createDefaultLayout();
    return new WriterAppender(getName(), actualLayout, getFilter(), getManager(target, follow, actualLayout),
            isIgnoreExceptions(), getPropertyArray());
}
 

private ColumnMapping(final String name, final String source, final StringLayout layout, final String literalValue, final String parameter, final Class<?> type) {
    this.name = name;
    this.nameKey = toKey(name);
    this.source = source;
    this.layout = layout;
    this.literalValue = literalValue;
    this.parameter = parameter;
    this.type = type;
}
 

public StringLayout getStringLayout() {
    return (StringLayout) getLayout();
}
 

@Override
protected StringLayout createLayout() {
    return PatternLayout.newBuilder().setCharset(StandardCharsets.UTF_8).setPattern("%m").build();
}
 

public StringLayout getStringLayout() {
    return (StringLayout) getLayout();
}
 

private static WriterManager getManager(final Writer target, final boolean follow, final StringLayout layout) {
    final Writer writer = new CloseShieldWriter(target);
    final String managerName = target.getClass().getName() + "@" + Integer.toHexString(target.hashCode()) + '.'
            + follow;
    return WriterManager.getManager(managerName, new FactoryData(writer, managerName, layout), factory);
}
 

private WriterAppender(final String name, final StringLayout layout, final Filter filter,
        final WriterManager manager, final boolean ignoreExceptions, Property[] properties) {
    super(name, layout, filter, ignoreExceptions, true, properties, manager);
}
 

public StringLayout getLayout() {
    return layout;
}
 

/**
 * Instantiates.
 * 
 * @param name
 *            The name of the Appender.
 * @param layout
 *            The layout to format the message.
 * @param properties Optional properties.
 * @param manager
 *            The OutputStreamManager.
 */
protected AbstractWriterAppender(final String name, final StringLayout layout, final Filter filter,
        final boolean ignoreExceptions, final boolean immediateFlush, Property[] properties, final M manager) {
    super(name, filter, layout, ignoreExceptions, properties);
    this.manager = manager;
    this.immediateFlush = immediateFlush;
}
 

/**
 * Creates a WriterAppender.
 * 
 * @param layout
 *            The layout to use or null to get the default layout.
 * @param filter
 *            The Filter or null.
 * @param target
 *            The target Writer
 * @param follow
 *            If true will follow changes to the underlying output stream.
 *            Use false as the default.
 * @param name
 *            The name of the Appender (required).
 * @param ignore
 *            If {@code "true"} (default) exceptions encountered when
 *            appending events are logged; otherwise they are propagated to
 *            the caller. Use true as the default.
 * @return The ConsoleAppender.
 */
@PluginFactory
public static WriterAppender createAppender(StringLayout layout, final Filter filter, final Writer target,
        final String name, final boolean follow, final boolean ignore) {
    if (name == null) {
        LOGGER.error("No name provided for WriterAppender");
        return null;
    }
    if (layout == null) {
        layout = PatternLayout.createDefaultLayout();
    }
    return new WriterAppender(name, layout, filter, getManager(target, follow, layout), ignore, Property.EMPTY_ARRAY);
}
 

/**
 * Builds instances.
 * 
 * @param writer
 *            The OutputStream.
 * @param type
 *            The name of the target.
 * @param layout
 *            A String layout
 */
public FactoryData(final Writer writer, final String type, final StringLayout layout) {
    this.writer = writer;
    this.name = type;
    this.layout = layout;
}
 

/**
 * Layout of value to write to database (before type conversion). Not applicable if {@link #setType(Class)} is
 * a {@link ReadOnlyStringMap}, {@link ThreadContextMap}, or {@link ThreadContextStack}.
 *
 * @return this.
 */
public Builder setLayout(final StringLayout layout) {
    this.layout = layout;
    return this;
}