摘要：既能設置大小，也能定時刷新無論是否達到設定的大小的適用于既想使用的提高性能，又想定時強制輸出以不影響某些依賴日志輸出的后續流程的場景默認的默認的定時刷新間隔秒下一次刷新的時間點默認的默認的至少秒本必須是否則沒意義配置使用樣例

package test;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import org.apache.log4j.DailyRollingFileAppender;
import org.apache.log4j.Layout;

/**
 * 既能設置buffer大小，也能定時刷新(無論是否達到設定的buffer大小)的appender;適用于既想使用buffer的IO提高性能，又想定時強制輸出以不影響某些依賴日志輸出的后續流程的場景
 * 
 * @author pf-miles
 * @since 2015-4-7
 */
public class TimedBufferedDailyRollingFileAppender extends DailyRollingFileAppender {

    private static final int                                         CHECK_INTERVAL      = 5;
    private static final Object                                      appendersLock       = new Object();
    private static final List appenders           = new ArrayList();
    static {
        new Thread(new Runnable() {

            public void run() {
                while (true) {
                    try {
                        synchronized (appendersLock) {
                            for (TimedBufferedDailyRollingFileAppender appender : appenders)
                                appender.flush();
                        }
                        Thread.sleep(CHECK_INTERVAL * 1000);
                    } catch (Throwable t) {
                        // ignore...
                    }
                }
            }
        }, "TimedBufferedDailyRollingFileAppender-timed-flush").start();
    }
    private static final int                                         DEFAULT_BUFFER_SIZE = 1024 * 1024;                                           // 默認1MB的buffer

    protected int                                                    flushInterval       = 60;                                                    // 默認的定時刷新間隔(秒)

    private Date                                                     flushTime           = new Date();                                            // 下一次刷新的時間點

    public TimedBufferedDailyRollingFileAppender(){
        super();
        this.setBufferedIO(true);
        this.setBufferSize(DEFAULT_BUFFER_SIZE);// 默認1MB的buffer
        this.setImmediateFlush(false);
        synchronized (appendersLock) {
            appenders.add(this);
        }
    }

    public TimedBufferedDailyRollingFileAppender(Layout layout, String filename, String datePattern) throws IOException{
        super(layout, filename, datePattern);
        this.setBufferedIO(true);
        this.setBufferSize(DEFAULT_BUFFER_SIZE);// 默認1MB的buffer
        this.setImmediateFlush(false);
        synchronized (appendersLock) {
            appenders.add(this);
        }
    }

    private void flush() {
        if (!(new Date()).after(flushTime)) return;
        if (!checkEntryConditions()) return;
        qw.flush();
        this.flushTime = new Date(System.currentTimeMillis() + this.flushInterval * 1000);
    }

    public void setFlushInterval(int flushInterval) {
        if (flushInterval < CHECK_INTERVAL) flushInterval = CHECK_INTERVAL;// 至少CHECK_INTERVAL秒
        this.flushInterval = flushInterval;
    }

    // 本appender必須是bufferedIO, 否則沒意義
    @Override
    public boolean getBufferedIO() {
        return true;
    }

    @Override
    public void setBufferedIO(boolean bufferedIO) {
        super.setBufferedIO(true);
    }

    @Override
    public void setImmediateFlush(boolean value) {
        super.setImmediateFlush(false);
    }

    @Override
    public boolean getImmediateFlush() {
        return false;
    }
}

配置使用樣例：