「log4j でエンコード指定できる SyslogAppendar を作る(おまけ)」ブログ用

SyslogAppendarTest.java

import java.io.FilterWriter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import org.apache.log4j.Layout;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.PatternLayout;
import org.apache.log4j.helpers.SyslogQuietWriter;
import org.apache.log4j.helpers.SyslogWriter;
import org.apache.log4j.net.SyslogAppender;

public class SyslogAppendarTest {

	public void execute(String syslogHost, int syslogFacility)
			throws NoSuchFieldException, IllegalAccessException {
		Layout layout = new PatternLayout("%d|%p|%m");
		SyslogAppender appender = new SyslogAppender(layout, syslogHost, syslogFacility);

		// Writer を入れ替える
		setEncodeSpecifiableWriter(appender, "UTF-8");

		Logger logger = Logger.getLogger(SyslogAppendarTest.class);
		logger.addAppender(appender);
		logger.setLevel(Level.WARN);
		logger.warn("警告ですよ！！");
	}

	private static void setEncodeSpecifiableWriter(
			SyslogAppender appender, String encode) throws NoSuchFieldException, IllegalAccessException {
		// SyslogAppender が持っている SyslogQuietWriter を取得
		Field sqwField = SyslogAppender.class.getDeclaredField("sqw");
		sqwField.setAccessible(true);
		SyslogQuietWriter writer = (SyslogQuietWriter) sqwField.get(appender);

		// SyslogQuietWriter が持っている SyslogWriter を EncodeSpecifiableSyslogWriter に入れ替える
		Field outField = FilterWriter.class.getDeclaredField("out");
		outField.setAccessible(true);
		outField.set(writer, new EncodeSpecifiableSyslogWriter(appender.getSyslogHost(), encode));
	}

	// SyslogWriter を継承した Writer を実装する。
	private static class EncodeSpecifiableSyslogWriter extends SyslogWriter {

		private final String encode;

		public EncodeSpecifiableSyslogWriter(String syslogHost, String encode) {
			super(syslogHost);
			this.encode = encode;
		}

		// write をオーバーライドする。string.getBytes(encode) 以外は親クラスと同じ。
		@Override
		public void write(String string) throws IOException {
			if (getDs() != null && getAddress() != null) {
				byte[] bytes = string.getBytes(encode);
				int bytesLength = bytes.length;
				if (bytesLength >= 1024)
					bytesLength = 1024;
				DatagramPacket packet = new DatagramPacket(
						bytes, bytesLength, getAddress(), getPort());
				getDs().send(packet);
			}
		}

		private DatagramSocket getDs() {
			try {
				Field field = SyslogWriter.class.getDeclaredField("ds");
				field.setAccessible(true);
				return (DatagramSocket) field.get(this);
			} catch (Exception e) {
				e.printStackTrace();
				return null;
			}
		}

		private InetAddress getAddress() {
			try {
				Field field = SyslogWriter.class.getDeclaredField("address");
				field.setAccessible(true);
				return (InetAddress) field.get(this);
			} catch (Exception e) {
				e.printStackTrace();
				return null;
			}
		}

		private int getPort() {
			try {
				Field field = SyslogWriter.class.getDeclaredField("port");
				field.setAccessible(true);
				return ((Integer) field.get(this)).intValue();
			} catch (Exception e) {
				e.printStackTrace();
				return 514;
			}
		}
	}

	public static void main(String[] args)
			throws NoSuchFieldException, IllegalAccessException {
		new SyslogAppendarTest().execute(
				"xxx.xxx.xxx.xxx", SyslogAppender.getFacility("LOCAL0"));
	}
}