日志文件自动删除功能必不可少，当然你可以让运维去做这事，只是这不地道。而日志组件是一个必备组件，让其多做一件删除的工作，无可厚非。本文就来探讨下 log4j 的日志文件自动删除实现吧。
0.自动删除配置参考样例: （log4j2.xml）
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<?xml version="1.0" encoding="UTF-8" ?>
<Configuration status="warn" monitorInterval="30" strict="true"
schema="Log4J-V2.2.xsd">
<Properties>
<Property name="log_level">info</Property>
</Properties>
<Appenders>
<!-- 输出到控制台 -->
<Console name="Console" target="SYSTEM_OUT">
<ThresholdFilter level="${log_level}" onMatch="ACCEPT" onMismatch="DENY" />
<PatternLayout pattern="%d{yyyy-MM-dd'T'HH:mm:ss.SSS} [%t] %p - %c - %m%n" />
</Console>
<!-- 与properties文件中位置存在冲突，如有问题，请注意调整 -->
<RollingFile name="logFile" fileName="logs/app/test.log"
filePattern="logs/app/history/test-%d{MM-dd-yyyy}-%i.log.gz">
<ThresholdFilter level="${log_level}" onMatch="ACCEPT" onMismatch="DENY" />
<PatternLayout pattern="%d{yyyy-MM-dd'T'HH:mm:ss.SSS} [%p] [%c:%L] -- %m%n" />
<Policies>
<!-- 按天递计算频率 -->
<TimeBasedTriggeringPolicy interval="1" />
<SizeBasedTriggeringPolicy size="500 MB" />
<OnStartupTriggeringPolicy />
</Policies>
<!-- 删除策略配置 -->
<DefaultRolloverStrategy max="5">
<Delete basePath="logs/app/history" maxDepth="1">
<IfFileName glob="*.log.gz"/>
<IfLastModified age="7d"/>
</Delete>
<Delete basePath="logs/app/history" maxDepth="1">
<IfFileName glob="*.docx"/>
</Delete>
<Delete basePath="logs/app/history" maxDepth="1">
<IfFileName glob="*.vsdx"/>
</Delete>
</DefaultRolloverStrategy>
</RollingFile>
<Async name="Async" bufferSize="2000" blocking="false">
<AppenderRef ref="logFile"/>
</Async>
</Appenders>
<Loggers>
<Root level="${log_level}">
<AppenderRef ref="Console" />
<AppenderRef ref="Async" />
</Root>
<!-- 配置个例 -->
<Logger name="com.xx.filter" level="info" />
</Loggers>
</Configuration>
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如果仅想停留在使用层面，如上log4j2.xml配置文件足矣！
不过，至少得注意一点，以上配置需要基于log4j2, 而如果你是 log4j1.x,则需要做下无缝升级：主要就是换下jar包版本，换个桥接包之类的,比如下参考配置：
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<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.2</version>
</dependency>
<!-- 桥接：告诉commons logging使用Log4j2 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>1.7.26</version>
</dependency>
<!-- 此处老版本，需注释掉 -->
<!--<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>-->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-compress</artifactId>
<version>1.10</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.8.2</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>2.8.2</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.8.2</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-web</artifactId>
<version>2.8.2</version>
</dependency>
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如果还想多了解一点其运行原理，就跟随本文的脚步吧:
1.自动清理大体运行流程
自动删除工作的运行原理大体流程如下。（大抵都是如此）
1. 加载log4j2.xml配置文件;
2. 读取appenders，并添加到log4j上下文中;
3. 加载 policy, 加载 rollover 配置;
4. 写入日志时判断是否满足rollover配置, 默认是一天运行一次, 可自行添加各种运行测试, 比如大小、启动时;
所以，删除策略的核心是每一次添加日志时。代码验证如下：
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// 在每次添加日志时判定
// org.apache.logging.log4j.core.appender.RollingRandomAccessFileAppender#append
/**
* Write the log entry rolling over the file when required.
*
* @param event The LogEvent.
*/
@Override
public void append(final LogEvent event) {
final RollingRandomAccessFileManager manager = getManager();
// 重点：直接检查是否需要 rollover, 如需要直接进行
manager.checkRollover(event);
// Leverage the nice batching behaviour of async Loggers/Appenders:
// we can signal the file manager that it needs to flush the buffer
// to disk at the end of a batch.
// From a user's point of view, this means that all log events are
// _always_ available in the log file, without incurring the overhead
// of immediateFlush=true.
manager.setEndOfBatch(event.isEndOfBatch()); // FIXME manager's EndOfBatch threadlocal can be deleted
// LOG4J2-1292 utilize gc-free Layout.encode() method: taken care of in superclass
super.append(event);
}
// org.apache.logging.log4j.core.appender.rolling.RollingFileManager#checkRollover
/**
* Determines if a rollover should occur.
* @param event The LogEvent.
*/
public synchronized void checkRollover(final LogEvent event) {
// 由各触发策略判定是否需要进行 rolling
// 如需要, 则调用 rollover()
if (triggeringPolicy.isTriggeringEvent(event)) {
rollover();
}
}
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所以，何时进行删除？答案是在适当的时机，这个时机可以是任意时候。
2. log4j 日志滚动
日志滚动，可以是重命名，也可以是删除文件。但总体判断是否可触发滚动的前提是一致的。我们这里主要关注文件删除。我们以时间作为依据看下判断过程。
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// 1. 判断是否是 触发事件时机
// org.apache.logging.log4j.core.appender.rolling.TimeBasedTriggeringPolicy#isTriggeringEvent
/**
* Determines whether a rollover should occur.
* @param event A reference to the currently event.
* @return true if a rollover should occur.
*/
@Override
public boolean isTriggeringEvent(final LogEvent event) {
if (manager.getFileSize() == 0) {
return false;
}
final long nowMillis = event.getTimeMillis();
// TimeBasedTriggeringPolicy, 是基于时间判断的, 此处为每天一次
if (nowMillis >= nextRolloverMillis) {
nextRolloverMillis = manager.getPatternProcessor().getNextTime(nowMillis, interval, modulate);
return true;
}
return false;
}
// org.apache.logging.log4j.core.appender.rolling.RollingFileManager#rollover()
public synchronized void rollover() {
if (!hasOutputStream()) {
return;
}
// strategy 是xml配置的策略
if (rollover(rolloverStrategy)) {
try {
size = 0;
initialTime = System.currentTimeMillis();
createFileAfterRollover();
} catch (final IOException e) {
logError("Failed to create file after rollover", e);
}
}
}
// RollingFileManager 统一管理触发器
// org.apache.logging.log4j.core.appender.rolling.RollingFileManager#rollover
private boolean rollover(final RolloverStrategy strategy) {
boolean releaseRequired = false;
try {
// Block until the asynchronous operation is completed.
// 上锁保证线程安全
semaphore.acquire();
releaseRequired = true;
} catch (final InterruptedException e) {
logError("Thread interrupted while attempting to check rollover", e);
return false;
}
boolean success = true;
try {
// 由各触发器运行 rollover 逻辑
final RolloverDescription descriptor = strategy.rollover(this);
if (descriptor != null) {
writeFooter();
closeOutputStream();
if (descriptor.getSynchronous() != null) {
LOGGER.debug("RollingFileManager executing synchronous {}", descriptor.getSynchronous());
try {
// 先使用同步方法，改名，然后再使用异步方法操作更多
success = descriptor.getSynchronous().execute();
} catch (final Exception ex) {
success = false;
logError("Caught error in synchronous task", ex);
}
}
// 如果配置了异步器, 则使用异步进行 rollover
if (success && descriptor.getAsynchronous() != null) {
LOGGER.debug("RollingFileManager executing async {}", descriptor.getAsynchronous());
// CompositeAction, 使用异步线程池运行用户的 action
asyncExecutor.execute(new AsyncAction(descriptor.getAsynchronous(), this));
// 在异步运行action期间，锁是不会被释放的，以避免线程安全问题
// 直到异步任务完成，再主动释放锁
releaseRequired = false;
}
return true;
}
return false;
} finally {
if (releaseRequired) {
semaphore.release();
}
}
}
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此处滚动有两个处理点，1. 每个滚动策略可以自行处理业务； 2. RollingFileManager 统一管理触发同步和异步的滚动action；
3. DefaultRolloverStrategy 默认滚动策略驱动
DefaultRolloverStrategy 作为一个默认的滚动策略实现，可以配置多个 Action, 然后处理删除操作。
删除有两种方式: 1. 当次滚动的文件数过多，会立即进行删除; 2. 配置单独的 DeleteAction, 根据配置的具体策略进行删除。（但该Action只会被返回给外部调用，自身则不会执行）
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// org.apache.logging.log4j.core.appender.rolling.DefaultRolloverStrategy#rollover
/**
* Performs the rollover.
*
* @param manager The RollingFileManager name for current active log file.
* @return A RolloverDescription.
* @throws SecurityException if an error occurs.
*/
@Override
public RolloverDescription rollover(final RollingFileManager manager) throws SecurityException {
int fileIndex;
// 默认 minIndex=1
if (minIndex == Integer.MIN_VALUE) {
final SortedMap<Integer, Path> eligibleFiles = getEligibleFiles(manager);
fileIndex = eligibleFiles.size() > 0 ? eligibleFiles.lastKey() + 1 : 1;
} else {
if (maxIndex < 0) {
return null;
}
final long startNanos = System.nanoTime();
// 删除case1: 获取符合条件的文件数，同时清理掉大于 max 配置的日志文件
// 如配置 max=5, 当前只有4个满足时, 不会立即清理文件, 但也不会阻塞后续流程
// 只要没有出现错误, fileIndex 不会小于0
fileIndex = purge(minIndex, maxIndex, manager);
if (fileIndex < 0) {
return null;
}
if (LOGGER.isTraceEnabled()) {
final double durationMillis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos);
LOGGER.trace("DefaultRolloverStrategy.purge() took {} milliseconds", durationMillis);
}
}
// 进入此区域即意味着，必然有文件需要滚动，重新命名了
final StringBuilder buf = new StringBuilder(255);
manager.getPatternProcessor().formatFileName(strSubstitutor, buf, fileIndex);
final String currentFileName = manager.getFileName();
String renameTo = buf.toString();
final String compressedName = renameTo;
Action compressAction = null;
FileExtension fileExtension = manager.getFileExtension();
if (fileExtension != null) {
renameTo = renameTo.substring(0, renameTo.length() - fileExtension.length());
compressAction = fileExtension.createCompressAction(renameTo, compressedName,
true, compressionLevel);
}
// 未发生文件重命名情况，即文件未被重命名未被滚动
// 该种情况应该不太会发生
if (currentFileName.equals(renameTo)) {
LOGGER.warn("Attempt to rename file {} to itself will be ignored", currentFileName);
return new RolloverDescriptionImpl(currentFileName, false, null, null);
}
// 新建一个重命令的 action, 返回待用
final FileRenameAction renameAction = new FileRenameAction(new File(currentFileName), new File(renameTo),
manager.isRenameEmptyFiles());
// 异步处理器，会处理用户配置的异步action，如本文配置的 DeleteAction
// 它将会在稍后被提交到异步线程池中运行
final Action asyncAction = merge(compressAction, customActions, stopCustomActionsOnError);
// 封装Rollover返回, renameAction 是同步方法, 其他用户配置的动态action 则是异步方法
// 删除case2: 封装异步返回action
return new RolloverDescriptionImpl(currentFileName, false, renameAction, asyncAction);
}
private int purge(final int lowIndex, final int highIndex, final RollingFileManager manager) {
// 默认使用 accending 的方式进行清理文件
return useMax ? purgeAscending(lowIndex, highIndex, manager) : purgeDescending(lowIndex, highIndex, manager);
}
// org.apache.logging.log4j.core.appender.rolling.DefaultRolloverStrategy#purgeAscending
/**
* Purges and renames old log files in preparation for rollover. The oldest file will have the smallest index, the
* newest the highest.
*
* @param lowIndex low index. Log file associated with low index will be deleted if needed.
* @param highIndex high index.
* @param manager The RollingFileManager
* @return true if purge was successful and rollover should be attempted.
*/
private int purgeAscending(final int lowIndex, final int highIndex, final RollingFileManager manager) {
final SortedMap<Integer, Path> eligibleFiles = getEligibleFiles(manager);
final int maxFiles = highIndex - lowIndex + 1;
boolean renameFiles = false;
// 依次迭代 eligibleFiles, 删除
while (eligibleFiles.size() >= maxFiles) {
try {
LOGGER.debug("Eligible files: {}", eligibleFiles);
Integer key = eligibleFiles.firstKey();
LOGGER.debug("Deleting {}", eligibleFiles.get(key).toFile().getAbsolutePath());
// 调用nio的接口删除文件
Files.delete(eligibleFiles.get(key));
eligibleFiles.remove(key);
renameFiles = true;
} catch (IOException ioe) {
LOGGER.error("Unable to delete {}, {}", eligibleFiles.firstKey(), ioe.getMessage(), ioe);
break;
}
}
final StringBuilder buf = new StringBuilder();
if (renameFiles) {
// 针对未完成删除的文件，继续处理
// 比如使用 匹配的方式匹配文件, 则不能被正常删除
// 还有些未超过maxFiles的文件
for (Map.Entry<Integer, Path> entry : eligibleFiles.entrySet()) {
buf.setLength(0);
// LOG4J2-531: directory scan & rollover must use same format
manager.getPatternProcessor().formatFileName(strSubstitutor, buf, entry.getKey() - 1);
String currentName = entry.getValue().toFile().getName();
String renameTo = buf.toString();
int suffixLength = suffixLength(renameTo);
if (suffixLength > 0 && suffixLength(currentName) == 0) {
renameTo = renameTo.substring(0, renameTo.length() - suffixLength);
}
Action action = new FileRenameAction(entry.getValue().toFile(), new File(renameTo), true);
try {
LOGGER.debug("DefaultRolloverStrategy.purgeAscending executing {}", action);
if (!action.execute()) {
return -1;
}
} catch (final Exception ex) {
LOGGER.warn("Exception during purge in RollingFileAppender", ex);
return -1;
}
}
}
// 此处返回的 findIndex 一定是 >=0 的
return eligibleFiles.size() > 0 ?
(eligibleFiles.lastKey() < highIndex ? eligibleFiles.lastKey() + 1 : highIndex) : lowIndex;
}
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4. 符合过滤条件的文件查找
当配置了 max 参数，这个参数是如何匹配的呢？比如我某个文件夹下有很历史文件，是否都会匹配呢？
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// 文件查找规则
// org.apache.logging.log4j.core.appender.rolling.AbstractRolloverStrategy#getEligibleFiles
protected SortedMap<Integer, Path> getEligibleFiles(final RollingFileManager manager) {
return getEligibleFiles(manager, true);
}
protected SortedMap<Integer, Path> getEligibleFiles(final RollingFileManager manager,
final boolean isAscending) {
final StringBuilder buf = new StringBuilder();
// 此处的pattern 即是在appender上配置的 filePattern, 一般会受限于 MM-dd-yyyy-$i.log.gz
String pattern = manager.getPatternProcessor().getPattern();
// 此处会将时间替换为当前, 然后按照此规则进行匹配要处理的文件
manager.getPatternProcessor().formatFileName(strSubstitutor, buf, NotANumber.NAN);
return getEligibleFiles(buf.toString(), pattern, isAscending);
}
// 细节匹配要处理的文件
protected SortedMap<Integer, Path> getEligibleFiles(String path, String logfilePattern, boolean isAscending) {
TreeMap<Integer, Path> eligibleFiles = new TreeMap<>();
File file = new File(path);
File parent = file.getParentFile();
if (parent == null) {
parent = new File(".");
} else {
parent.mkdirs();
}
if (!logfilePattern.contains("%i")) {
return eligibleFiles;
}
Path dir = parent.toPath();
String fileName = file.getName();
int suffixLength = suffixLength(fileName);
if (suffixLength > 0) {
fileName = fileName.substring(0, fileName.length() - suffixLength) + ".*";
}
String filePattern = fileName.replace(NotANumber.VALUE, "(\\d+)");
Pattern pattern = Pattern.compile(filePattern);
try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir)) {
for (Path entry: stream) {
// 该匹配相当精确
// 只会删除当天或者在时间交替的时候删除上一天的数据咯
// 如果在这个时候进行了重启操作，就再也不会删除此文件了
Matcher matcher = pattern.matcher(entry.toFile().getName());
if (matcher.matches()) {
Integer index = Integer.parseInt(matcher.group(1));
eligibleFiles.put(index, entry);
}
}
} catch (IOException ioe) {
throw new LoggingException("Error reading folder " + dir + " " + ioe.getMessage(), ioe);
}
return isAscending? eligibleFiles : eligibleFiles.descendingMap();
}
// 此处会将 各种格式的文件名，替换为当前时间或者最后一次滚动的文件的时间。所以匹配的时候，并不会匹配超时当前认知范围的文件
/**
* Formats file name.
* @param subst The StrSubstitutor.
* @param buf string buffer to which formatted file name is appended, may not be null.
* @param obj object to be evaluated in formatting, may not be null.
*/
public final void formatFileName(final StrSubstitutor subst, final StringBuilder buf, final boolean useCurrentTime,
final Object obj) {
// LOG4J2-628: we deliberately use System time, not the log4j.Clock time
// for creating the file name of rolled-over files.
final long time = useCurrentTime && currentFileTime != 0 ? currentFileTime :
prevFileTime != 0 ? prevFileTime : System.currentTimeMillis();
formatFileName(buf, new Date(time), obj);
final LogEvent event = new Log4jLogEvent.Builder().setTimeMillis(time).build();
final String fileName = subst.replace(event, buf);
buf.setLength(0);
buf.append(fileName);
}
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AsyncAction 是一个 Runnable 的实现, 被直接提交到线程池运行. AsyncAction -> AbstractAction -> Action -> Runnable
它是一个统一管理异步Action的包装，主要是管理锁和异常类操作。
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// org.apache.logging.log4j.core.appender.rolling.RollingFileManager.AsyncAction
/**
* Performs actions asynchronously.
*/
private static class AsyncAction extends AbstractAction {
private final Action action;
private final RollingFileManager manager;
/**
* Constructor.
* @param act The action to perform.
* @param manager The manager.
*/
public AsyncAction(final Action act, final RollingFileManager manager) {
this.action = act;
this.manager = manager;
}
/**
* Executes an action.
*
* @return true if action was successful. A return value of false will cause
* the rollover to be aborted if possible.
* @throws java.io.IOException if IO error, a thrown exception will cause the rollover
* to be aborted if possible.
*/
@Override
public boolean execute() throws IOException {
try {
// 门面调用 action.execute(), 一般是调用 CompositeAction, 里面封装了多个 action
return action.execute();
} finally {
// 任务执行完成，才会释放外部的锁
// 虽然不是很优雅，但是很准确很安全
manager.semaphore.release();
}
}
...
}
// CompositeAction 封装了多个 action 处理
// org.apache.logging.log4j.core.appender.rolling.action.CompositeAction#run
/**
* Execute sequence of actions.
*
* @return true if all actions were successful.
* @throws IOException on IO error.
*/
@Override
public boolean execute() throws IOException {
if (stopOnError) {
// 依次调用action
for (final Action action : actions) {
if (!action.execute()) {
return false;
}
}
return true;
}
boolean status = true;
IOException exception = null;
for (final Action action : actions) {
try {
status &= action.execute();
} catch (final IOException ex) {
status = false;
if (exception == null) {
exception = ex;
}
}
}
if (exception != null) {
throw exception;
}
return status;
}
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DeleteAction是我们真正关心的动作。
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// CompositeAction 封装了多个 action 处理
// org.apache.logging.log4j.core.appender.rolling.action.CompositeAction#run
/**
* Execute sequence of actions.
*
* @return true if all actions were successful.
* @throws IOException on IO error.
*/
@Override
public boolean execute() throws IOException {
if (stopOnError) {
// 依次调用action
for (final Action action : actions) {
if (!action.execute()) {
return false;
}
}
return true;
}
boolean status = true;
IOException exception = null;
for (final Action action : actions) {
try {
status &= action.execute();
} catch (final IOException ex) {
status = false;
if (exception == null) {
exception = ex;
}
}
}
if (exception != null) {
throw exception;
}
return status;
}
// DeleteAction 做真正的删除动作
// org.apache.logging.log4j.core.appender.rolling.action.DeleteAction#execute()
@Override
public boolean execute() throws IOException {
// 如果没有script配置，则直接委托父类处理
return scriptCondition != null ? executeScript() : super.execute();
}
org.apache.logging.log4j.core.appender.rolling.action.AbstractPathAction#execute()
@Override
public boolean execute() throws IOException {
// 根据指定的basePath, 和过滤条件，选择相关文件
// 调用 DeleteAction 的 createFileVisitor(), 返回 DeletingVisitor
return execute(createFileVisitor(getBasePath(), pathConditions));
}
// org.apache.logging.log4j.core.appender.rolling.action.DeleteAction#execute(java.nio.file.FileVisitor<java.nio.file.Path>)
@Override
public boolean execute(final FileVisitor<Path> visitor) throws IOException {
// 根据maxDepth设置，遍历所有可能的文件路径
// 使用 Files.walkFileTree() 实现, 添加到 collected 中
final List<PathWithAttributes> sortedPaths = getSortedPaths();
trace("Sorted paths:", sortedPaths);
for (final PathWithAttributes element : sortedPaths) {
try {
// 依次调用 visitFile, 依次判断是否需要删除
visitor.visitFile(element.getPath(), element.getAttributes());
} catch (final IOException ioex) {
LOGGER.error("Error in post-rollover Delete when visiting {}", element.getPath(), ioex);
visitor.visitFileFailed(element.getPath(), ioex);
}
}
// TODO return (visitor.success || ignoreProcessingFailure)
return true; // do not abort rollover even if processing failed
}
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最终，即和想像的一样：找到要查找的文件夹，遍历各文件，用多个条件判断是否满足。删除符合条件的文件。
只是这其中注意的点：如何删除文件的线程安全性；如何保证删除工作不影响业务线程；很常见的锁和多线程的应用。
5.真正的删除
真正的删除动作就是在DeleteAction中配置的，但上面可以看它是调用visitor的visitFile方法，所以有必要看看是如何真正处理删除的。（实际上前面在purge时已经做过一次删除操作了，所以别被两个点迷惑了，建议尽量只依赖于Delete配置，可以将外部max设置很大以避免两处生效）
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// org.apache.logging.log4j.core.appender.rolling.action.DeletingVisitor#visitFile
@Override
public FileVisitResult visitFile(final Path file, final BasicFileAttributes attrs) throws IOException {
for (final PathCondition pathFilter : pathConditions) {
final Path relative = basePath.relativize(file);
// 遍历所有条件，只要有一个不符合，即不进行删除。
// 所以，所以条件是 AND 关系， 没有 OR 关系
// 如果想配置 OR 关系，只能配置多个DELETE
if (!pathFilter.accept(basePath, relative, attrs)) {
LOGGER.trace("Not deleting base={}, relative={}", basePath, relative);
return FileVisitResult.CONTINUE;
}
}
// 直接删除文件
if (isTestMode()) {
LOGGER.info("Deleting {} (TEST MODE: file not actually deleted)", file);
} else {
delete(file);
}
return FileVisitResult.CONTINUE;
}
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删除策略配置比如:
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<RollingFile name="logFile" fileName="logs/app/test.log"
filePattern="logs/app/history/test-%d{MM-dd-yyyy}-%i.log.gz">
<ThresholdFilter level="${log_level}" onMatch="ACCEPT" onMismatch="DENY" />
<PatternLayout pattern="%d{yyyy-MM-dd'T'HH:mm:ss.SSS} [%p] [%c:%L] -- %m%n" />
<Policies>
<!-- 按天递计算频率 -->
<TimeBasedTriggeringPolicy interval="1" />
<SizeBasedTriggeringPolicy size="500 MB" />
<OnStartupTriggeringPolicy />
</Policies>
<!-- 删除策略配置 -->
<DefaultRolloverStrategy max="5000">
<Delete basePath="logs/app/history" maxDepth="1">
<!-- 配置且关系 -->
<IfFileName glob="*.log.gz"/>
<IfLastModified age="7d"/>
</Delete>
<!-- 配置或关系 -->
<Delete basePath="logs/app/history" maxDepth="1">
<IfFileName glob="*.docx"/>
</Delete>
<Delete basePath="logs/app/history" maxDepth="1">
<IfFileName glob="*.vsdx"/>
</Delete>
</DefaultRolloverStrategy>
</RollingFile>
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另外说明，之所以能够无缝替换，是因为利用了不同实现版本的 org/slf4j/impl/StaticLoggerBinder.class, 而外部都使用 slf4j 接口定义实现的，比如 org.apache.logging.log4j:log4j-slf4j-impl 包的实现。
总结
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原文链接：https://www.cnblogs.com/yougewe/p/13407812.html