log4j提供了标准的日志输出，简单配置即可记录日志（参考Spring Boot入门：使用AOP实现拦截器 8、日志记录），但使用默认Appender记录日志时，有时并不能满足我们的需求，这时我们可以自定义log4j日志输出格式。
下面我们实现按日期记录日志，日志达到指定大小后重命名保存为新文件。
首先新建GlobalRollingFileAppender继承RollingFileAppender
import org.apache.log4j.RollingFileAppender;
import org.apache.log4j.helpers.CountingQuietWriter;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;
import java.io.File;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class GlobalRollingFileAppender extends RollingFileAppender {
private long nextRollover = 0L;
private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMdd");
public void rollOver() {
if (qw != null) {
long size = ((CountingQuietWriter) qw).getCount();
LogLog.debug("rolling over count=" + size);
nextRollover = size + maxFileSize;
}
LogLog.debug("maxBackupIndex=" + maxBackupIndex);
boolean renameSucceeded = true;
if (maxBackupIndex > 0) {
File file;
File target;
for (int i = maxBackupIndex - 1; i >= 1 && renameSucceeded; i--) {
file = new File(genFileName(fileName, i));
if (file.exists()) {
target = new File(genFileName(fileName, i + 1));
LogLog.debug("Renaming file " + file + " to " + target);
renameSucceeded = file.renameTo(target);
}
}
if (renameSucceeded) {
target = new File(genFileName(fileName, 1));
this.closeFile();
file = new File(fileName);
LogLog.debug("Renaming file " + file + " to " + target);
renameSucceeded = file.renameTo(target);
if (!renameSucceeded) {
try {
this.setFile(fileName, true, bufferedIO, bufferSize);
} catch (IOException e) {
if (e instanceof InterruptedIOException) {
Thread.currentThread().interrupt();
}
LogLog.error("setFile(" + fileName + ", true) call failed.", e);
}
}
}
}
if (renameSucceeded) {
try {
this.setFile(fileName, false, bufferedIO, bufferSize);
nextRollover = 0L;
} catch (IOException e) {
if (e instanceof InterruptedIOException) {
Thread.currentThread().interrupt();
}
LogLog.error("setFile(" + fileName + ", false) call failed.", e);
}
}
}
private String genFileName(String name, int index) {
String fileName;
if (index > 0) {
String num = index < 10 ? "0" + index : String.valueOf(index);
fileName = name.replace(".log", "") + "_" + num + ".log";
} else {
fileName = name;
}
return fileName;
}
protected void subAppend(LoggingEvent event) {
boolean flag = false;
String fileNameNow = fileName.substring(fileName.lastIndexOf("/"));
String fileNameDate = simpleDateFormat.format(new Date());
if (!fileNameNow.contains(fileNameDate)) {
flag = true;
int tag = fileNameNow.indexOf("_");
fileName = fileName.replace(fileNameNow.substring(tag + 1, tag + 9), fileNameDate);
}
if (fileName != null && qw != null) {
long size = ((CountingQuietWriter) qw).getCount();
if (flag) {
size = 0L;
}
if ((size >= maxFileSize && size >= nextRollover) || flag) {
rollOver();
}
}
super.subAppend(event);
}
public void setFile(String file) {
fileName = file.trim().replace(".log", "") +
"_" + simpleDateFormat.format(new Date()) + ".log";
}
}
然后我们将log4j.properties日志输出appender设为GlobalRollingFileAppender ，即log4j.appender.logInfo=cn.wbnull.springbootdemo.boot.GlobalRollingFileAppender
log4j.rootLogger=debug,Console,logInfo,logError,logDebug
log4j.category.org.springframework=debug,Console,logInfo,logError,logDebug
#
#输出到控制台
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.Target=System.out
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=[%p][%d{yyyy-MM-dd HH\:mm\:ss,SSS}][%C.%M(%F\:%L)] || %m%n
#
#输出到文件
log4j.appender.logInfo=cn.wbnull.springbootdemo.boot.GlobalRollingFileAppender
log4j.appender.logInfo.File=./logs/log.log
log4j.appender.logInfo.Append=true
log4j.appender.logInfo.Threshold=INFO
log4j.appender.logInfo.MaxFileSize=2048KB
log4j.appender.logInfo.MaxBackupIndex=1024
log4j.appender.logInfo.layout=org.apache.log4j.PatternLayout
log4j.appender.logInfo.layout.ConversionPattern=[%p][%d{yyyy-MM-dd HH\:mm\:ss,SSS}][%C.%M(%F\:%L)] || %m%n
#
#错误日志单独记录
log4j.appender.logError=cn.wbnull.springbootdemo.boot.GlobalRollingFileAppender
log4j.appender.logError.File=./logs/error.log
log4j.appender.logError.Append=true
log4j.appender.logError.Threshold=ERROR
log4j.appender.logError.MaxFileSize=2048KB
log4j.appender.logError.MaxBackupIndex=1024
log4j.appender.logError.layout=org.apache.log4j.PatternLayout
log4j.appender.logError.layout.ConversionPattern=[%p][%d{yyyy-MM-dd HH\:mm\:ss,SSS}][%C.%M(%F\:%L)] || %m%n
#
#Debug日志单独记录
log4j.appender.logDebug=cn.wbnull.springbootdemo.boot.GlobalRollingFileAppender
log4j.appender.logDebug.File=./logs/debug.log
log4j.appender.logDebug.Append=true
log4j.appender.logDebug.Threshold=DEBUG
log4j.appender.logDebug.MaxFileSize=2048KB
log4j.appender.logDebug.MaxBackupIndex=1024
log4j.appender.logDebug.layout=org.apache.log4j.PatternLayout
log4j.appender.logDebug.filter.infoFilter=org.apache.log4j.varia.LevelRangeFilter
log4j.appender.logDebug.filter.infoFilter.LevelMin=DEBUG
log4j.appender.logDebug.filter.infoFilter.LevelMax=DEBUG
log4j.appender.logDebug.layout.ConversionPattern=[%p][%d{yyyy-MM-dd HH\:mm\:ss,SSS}][%C.%M(%F\:%L)] || %m%n
GitHub：github.com/dkbnull/spr…
Gitee：gitee.com/dkbnull/spr…
CSDN：blog.csdn.net/dkbnull/art…
微信：mp.weixin.qq.com/s/TY0lb921o…
知乎：zhuanlan.zhihu.com/p/95405807
