log4j按日期输出日志的同时限制保存的个数

Appender为日志输出目的地, log4j已经提供了非常丰富的Appender用以满足不同的需求:

• org.apache.log4j.ConsoleAppender 输出到控制台
• org.apache.log4j.FileAppender 输出到文件
• org.apache.log4j.DailyRollingFileAppender 每天产生一个日志文件
• org.apache.log4j.RollingFileAppender 文件大小到达指定尺寸的时候产生一个新的文件
• org.apache.log4j.WriterAppender 将日志信息以流格式发送到任意指定的地方

可见, 丰富的功能已经可以满足我们的大部分需求, 但是有时候我们需要按日期归档每日的log, 又不想保留太多的文件, 比如只要最近三天, 或者一周就好了. 这个时候就只能我们自己写Appender了:

package pplive.auth.conf;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Layout;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;

/**
 * 扩展的一个按天滚动的appender类, 暂时不支持datePattern设置, 但是可以配置maxBackupIndex
 * 
 * @author Dan Shan
 *
 */
public class CustomLogAppender extends FileAppender {

    /** 不允许改写的datepattern */
    private static final String datePattern = "'.'yyyy-MM-dd";
    /** 最多文件增长个数 */
    private int maxBackupIndex = 2;
    /** 文件名+上次最后更新时间 */
    private String scheduledFilename;
    
    /**
     * The next time we estimate a rollover should occur.
     */
    private long nextCheck = System.currentTimeMillis() - 1;

    Date now = new Date();
    SimpleDateFormat sdf;

    /**
     * The default constructor does nothing.
     */
    public CustomLogAppender() {
    }

    /**
     * 改造过的构造器
     */
    public CustomLogAppender(Layout layout, String filename, int maxBackupIndex) throws IOException {
        super(layout, filename, true);
        this.maxBackupIndex = maxBackupIndex;
        activateOptions();
    }
    
    /** * 初始化本Appender对象的时候调用一次 */
    @Override
    public void activateOptions() {
        super.activateOptions();
        if (fileName != null) {
            // perf.log now.setTime(System.currentTimeMillis());
            sdf = new SimpleDateFormat(datePattern);
            File file = new File(fileName);
            // 获取最后更新时间拼成的文件名
            scheduledFilename = fileName + sdf.format(new Date(file.lastModified()));
        } else {
            LogLog.error("File is not set for appender [" + name + "].");
        } if (maxBackupIndex <= 0) {
            LogLog.error("maxBackupIndex reset to default value[2],orignal value is:" + maxBackupIndex);
            maxBackupIndex = 2;
        }
    }
    
    /**
     * 滚动文件的函数:<br>
     * 1. 对文件名带的时间戳进行比较, 确定是否更新<br>
     * 2. if需要更新, 当前文件rename到文件名+日期, 重新开始写文件<br>
     * 3. 针对配置的maxBackupIndex,删除过期的文件
     */
    void rollOver() throws IOException {
        String datedFilename = fileName + sdf.format(now);
        // 如果上次写的日期跟当前日期相同，不需要换文件
        if (scheduledFilename.equals(datedFilename)) {
            return;
        }
        // close current file, and rename it to datedFilename 
        this.closeFile();
        File target = new File(scheduledFilename);
        if (target.exists()) {
            try {
                target.delete();
            } catch (SecurityException e) {
                e.printStackTrace();
            }
        }

        File file = new File(fileName);
        boolean result = file.renameTo(target);
        if (result) {
            LogLog.debug(fileName + " -> " + scheduledFilename);
        } else {
            LogLog.error("Failed to rename [" + fileName + "] to [" + scheduledFilename + "].");
        }
        
        // 删除过期文件
        if (maxBackupIndex > 0) {
            File folder = new File(file.getParent());
            List<String> maxBackupIndexDates = getMaxBackupIndexDates();
            for (File ff : folder.listFiles()) {
                // 遍历目录，将日期不在备份范围内的日志删掉
                if (ff.getName().startsWith(file.getName()) && !ff.getName().equals(file.getName())) {
                    // 获取文件名带的日期时间戳
                    String markedDate = ff.getName().substring( file.getName().length());
                    if (!maxBackupIndexDates.contains(markedDate)) {
                        result = ff.delete();
                    }
                    if (result) {
                        LogLog.debug(ff.getName() + " -> deleted ");
                    } else {
                        LogLog.error("Failed to deleted old DayRollingFileAppender file :" + ff.getName());
                    }
                }
            }    
        }
        
        try {
            // This will also close the file. This is OK since multiple
            // close operations are safe. 
            this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
        } catch (IOException e) {
            errorHandler.error("setFile(" + fileName + ", false) call failed.");
        }
        
        scheduledFilename = datedFilename;
        // 更新最后更新日期戳 
    }
    
    /**
     * Actual writing occurs here.
     * 这个方法是写操作真正的执行过程.
     */
    @Override
    protected void subAppend(LoggingEvent event) {
        
        long n = System.currentTimeMillis();
        if (n >= nextCheck) {
        
            // 在每次写操作前判断一下是否需要滚动文件
            now.setTime(n);
            nextCheck = getNextDayCheckPoint(now);
            try {
                rollOver();
            } catch (IOException ioe) {
                LogLog.error("rollOver() failed.", ioe);
            }
        } super.subAppend(event);
    }
    
    /**
     * 获取下一天的时间变更点
     *
     * @param now
     * @return
     */
    long getNextDayCheckPoint(Date now) {
    
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(now);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);// 注意MILLISECOND,毫秒也要置0.。。否则错了也找不出来的 calendar.add(Calendar.DATE, 1);
        return calendar.getTimeInMillis();
    }

    /**
     * 根据maxBackupIndex配置的备份文件个数，获取要保留log文件的日期范围集合
     * @return list<'fileName+yyyy-MM-dd'>
     */
    List<String> getMaxBackupIndexDates() {
        
        List<String> result = new ArrayList<String>();
        if (maxBackupIndex > 0) {
            for (int i = 1; i <= maxBackupIndex; i++) {
                Calendar calendar = Calendar.getInstance();
                calendar.setTime(now);
                calendar.set(Calendar.HOUR_OF_DAY, 0);
                calendar.set(Calendar.MINUTE, 0);
                calendar.set(Calendar.SECOND, 0);
                calendar.set(Calendar.MILLISECOND, 0);
                
                // 注意MILLISECOND,毫秒也要置0...否则错了也找不出来的
                calendar.add(Calendar.DATE, -i);
                result.add(sdf.format(calendar.getTime()));
            }
        }
        
        return result;
    }
    
    public int getMaxBackupIndex() {
        return maxBackupIndex;
    }
    public void setMaxBackupIndex(int maxBackupIndex) {
        this.maxBackupIndex = maxBackupIndex;
    }
    public String getDatePattern() {
        return datePattern;
    }
}

在log4j.properties中定义如下

log4j.rootLogger=INFO, A1
log4j.appender.A1=pplive.auth.conf.CustomLogAppender
log4j.appender.A1.File=/auth.log

# 输出的文件目录
log4j.appender.A1.maxBackupIndex=7
# 保存的天数
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%d{HH:mm:ss,SSS} %c{1} %M %m%n