分享代码片段：既能设置buffer大小，也能定时刷新(无论是否达到设定的buffer大小)的log4

摘要：既能设置大小，也能定时刷新无论是否达到设定的大小的适用于既想使用的提高性能，又想定时强制输出以不影响某些依赖日志输出的后续流程的场景默认的默认的定时刷新间隔秒下一次刷新的时间点默认的默认的至少秒本必须是否则没意义配置使用样例

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;

/**
 * 既能设置buffer大小，也能定时刷新(无论是否达到设定的buffer大小)的appender;适用于既想使用buffer的IO提高性能，又想定时强制输出以不影响某些依赖日志输出的后续流程的场景
 * 
 * @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;                                           // 默认1MB的buffer

    protected int                                                    flushInterval       = 60;                                                    // 默认的定时刷新间隔(秒)

    private Date                                                     flushTime           = new Date();                                            // 下一次刷新的时间点

    public TimedBufferedDailyRollingFileAppender(){
        super();
        this.setBufferedIO(true);
        this.setBufferSize(DEFAULT_BUFFER_SIZE);// 默认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);// 默认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必须是bufferedIO, 否则没意义
    @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;
    }
}

配置使用样例：