当log4j使用DailyRollingFileAppender进行日志归档时，需要对日志的个数进行控制。
此时需要对DailyRollingFileAppender进行重写。
package org.apache.log4j;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.text.ParseException;
import java.util.*;public class MyDailyRollingFileAppender extends DailyRollingFileAppender {private static Logger logger = LoggerFactory.getLogger(MyDailyRollingFileAppender.class);private int maxFileSize = 60;@Overridevoid rollOver() throws IOException {super.rollOver();List<File> fileList = getAllLogs();sortFiles(fileList);logger.debug(fileList.toString());deleteOvermuch(fileList);}/*** 删除过多的文件* @param fileList 所有日志文件*/private void deleteOvermuch(List<File> fileList) {if (fileList.size() > maxFileSize) {for (int i = 0;i < fileList.size() - maxFileSize;i++) {fileList.get(i).delete();logger.debug("删除日志" + fileList.get(i));}}}/*** 根据文件名称上的特定格式的时间排序日志文件* @param fileList*/private void sortFiles(List<File> fileList) {Collections.sort(fileList, new Comparator<File>() {public int compare(File o1, File o2) {try {if (getDateStr(o1).isEmpty()) {return 1;}Date date1 = sdf.parse(getDateStr(o1));if (getDateStr(o2).isEmpty()) {return -1;}Date date2 = sdf.parse(getDateStr(o2));if (date1.getTime() > date2.getTime()) {return 1;} else if (date1.getTime() < date2.getTime()) {return -1;}} catch (ParseException e) {logger.error("", e);}return 0;}});}private String getDateStr(File file) {if (file == null) {return "null";}return file.getName().replaceAll(new File(fileName).getName(), "");}/*** 获取所有日志文件，只有文件名符合DatePattern格式的才为日志文件* @return*/private List<File> getAllLogs() {final File file = new File(fileName);File logPath = file.getParentFile();if (logPath == null) {logPath = new File(".");}File files[] = logPath.listFiles(new FileFilter() {public boolean accept(File pathname) {try {if (getDateStr(pathname).isEmpty()) {return true;}sdf.parse(getDateStr(pathname));return true;} catch (ParseException e) {logger.error("", e);return false;}}});return Arrays.asList(files);}public int getMaxFileSize() {return maxFileSize;}public void setMaxFileSize(int maxFileSize) {this.maxFileSize = maxFileSize;}
}
然后在log4j的properties文件中添加
log4j.appender.R=org.apache.log4j.MyDailyRollingFileAppender
log4j.appender.R.MaxFileSize=30