好的，通过像here 中描述的那样扩展 DefaultRolloverStrategy 可以解决这个问题。但是
- 它需要大约 150 行代码（包括包装 RolloverDescription 和 appender.rolling.helper.Action）和
- 有点味道，因为需要完全复制 DefaultRolloverStrategy 的工厂方法（使此解决方案维护不友好，例如，如果 DefaultRolloverStrategy 在未来版本中获取更多配置参数）
要让log4j2调用我们的工厂方法，log4j2.xml的根标签必须带有我们类的包，例如：
<Configuration packages="de.jme.toolbox.logging">
...
</Configuration>
在我们自己的 RolloverStrategy 中，我们必须按照 here 的描述处理 @Plugin 和 @PluginFactory。
最后是我完整的 log4j2.xml（您不需要所有这些属性 - 这正是我喜欢配置日志记录的方式）：
<?xml version="1.0" encoding="UTF-8"?>
<Configuration packages="de.jme.toolbox.logging">
<Properties>
<Property name="projectPrefix">Tts</Property>
<Property name="rawPattern">%d %-5p [%t] %C{2} (%F:%L) - %m%n</Property>
<Property name="coloredPattern">%d %highlight{%-5p}{FATAL=bright red, ERROR=red, WARN=yellow, INFO=cyan, DEBUG=green, TRACE=bright blue} %style{[%t] %C{2} (%F:%L) -}{bright,black} %m%n</Property>
<Property name="coloredShortPattern">%d %highlight{%-5p}{FATAL=bright red, ERROR=red, WARN=yellow, INFO=cyan, DEBUG=green, TRACE=bright blue} %style{[%t] -}{bright,black} %m%n</Property>
<Property name="fileName">Log/${projectPrefix}.log</Property>
<Property name="filePattern">Log/${projectPrefix}-%i.log</Property>
</Properties>
<Appenders>
<Console name="Stdout" target="SYSTEM_OUT">
<PatternLayout pattern="${coloredPattern}"/>
</Console>
<RollingFile name="Logfile" fileName="${fileName}" filePattern="${filePattern}">
<PatternLayout pattern="${rawPattern}"/>
<Policies>
<SizeBasedTriggeringPolicy size="1 MB"/>
</Policies>
<MyRolloverStrategy fileIndex="min" max="16"/>
</RollingFile>
</Appenders>
<Loggers>
<Root level="info">
<AppenderRef ref="Stdout"/>
<AppenderRef ref="Logfile"/>
</Root>
</Loggers>
</Configuration>
这里是 MyRolloverStrategy.java：
package de.jme.toolbox.logging;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.zip.Deflater;
import org.apache.logging.log4j.core.appender.rolling.DefaultRolloverStrategy;
import org.apache.logging.log4j.core.appender.rolling.RollingFileManager;
import org.apache.logging.log4j.core.appender.rolling.RolloverDescription;
import org.apache.logging.log4j.core.appender.rolling.helper.Action;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.helpers.Integers;
import org.apache.logging.log4j.core.lookup.StrSubstitutor;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.status.StatusLogger;
/**
* Own RolloverStrategy to hook the DefaultRolloverStrategy's rollover events
*
* Siehe auch:
* - https://issues.apache.org/jira/browse/LOG4J2-486
* - http://apache-logging.6191.n7.nabble.com/log4j2-getting-started-amp-rolling-files-tt8406.html#a42402
* - http://stackoverflow.com/questions/20819376/log4j2-rollingfile-appender-add-custom-info-at-the-start-of-each-logfile
*
* @author Joe Merten
*/
@org.apache.logging.log4j.core.config.plugins.Plugin(name="MyRolloverStrategy", category="Core", printObject=true)
public class MyRolloverStrategy extends DefaultRolloverStrategy {
protected static final Logger logger = StatusLogger.getLogger();
// ==============================
// ↓↓↓ Some stuff copied from ↓↓↓
// https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/DefaultRolloverStrategy.java r1556050
// Just changed »DefaultRolloverStrategy« to »MyRolloverStrategy«
private static final int MIN_WINDOW_SIZE = 1;
private static final int DEFAULT_WINDOW_SIZE = 7;
@PluginFactory
public static MyRolloverStrategy createStrategy(
@PluginAttribute("max") final String max,
@PluginAttribute("min") final String min,
@PluginAttribute("fileIndex") final String fileIndex,
@PluginAttribute("compressionLevel") final String compressionLevelStr,
@PluginConfiguration final Configuration config) {
final boolean useMax = fileIndex == null ? true : fileIndex.equalsIgnoreCase("max");
int minIndex;
if (min != null) {
minIndex = Integer.parseInt(min);
if (minIndex < 1) {
LOGGER.error("Minimum window size too small. Limited to " + MIN_WINDOW_SIZE);
minIndex = MIN_WINDOW_SIZE;
}
} else {
minIndex = MIN_WINDOW_SIZE;
}
int maxIndex;
if (max != null) {
maxIndex = Integer.parseInt(max);
if (maxIndex < minIndex) {
maxIndex = minIndex < DEFAULT_WINDOW_SIZE ? DEFAULT_WINDOW_SIZE : minIndex;
LOGGER.error("Maximum window size must be greater than the minimum windows size. Set to " + maxIndex);
}
} else {
maxIndex = DEFAULT_WINDOW_SIZE;
}
final int compressionLevel = Integers.parseInt(compressionLevelStr, Deflater.DEFAULT_COMPRESSION);
return new MyRolloverStrategy(minIndex, maxIndex, useMax, compressionLevel, config.getStrSubstitutor());
}
// ↑↑↑ Some stuff copied from ↑↑↑
// ==============================
protected MyRolloverStrategy(int minIndex, int maxIndex, boolean useMax, int compressionLevel, StrSubstitutor subst) {
super(minIndex, maxIndex, useMax, compressionLevel, subst);
}
// Wrapper class only for setting a hook to execute()
static class MyAction implements Action {
final Action delegate;
final String fileName;
public MyAction(final Action delegate, final String fileName) {
this.delegate = delegate;
this.fileName = fileName;
}
@Override public void run() {
delegate.run();
}
@Override public boolean execute() throws IOException {
try {
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new FileWriter(new File(fileName), true));
writer.write("****************************\n");
writer.write("*** Bye, bye old logfile ***\n");
writer.write("****************************\n");
} finally {
if (writer != null)
writer.close();
}
} catch (Throwable e) {
logger.error("Writing to bottom of old logfile \"" + fileName + "\" with", e);
}
boolean ret = delegate.execute();
try {
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new FileWriter(new File(fileName), true));
writer.write("*************************\n");
writer.write("*** Hello new logfile ***\n");
writer.write("*************************\n");
} finally {
if (writer != null)
writer.close();
}
} catch (Throwable e) {
logger.error("Writing to top of new logfile \"" + fileName + "\" with", e);
}
return ret;
}
@Override public void close() {
delegate.close();
}
@Override public boolean isComplete() {
return delegate.isComplete();
}
}
// Wrapper class only for setting a hook to getSynchronous().execute()
static class MyRolloverDescription implements RolloverDescription {
final RolloverDescription delegate;
public MyRolloverDescription(final RolloverDescription delegate) {
this.delegate = delegate;
}
@Override public String getActiveFileName() {
return delegate.getActiveFileName();
}
@Override public boolean getAppend() {
//return delegate.getAppend();
// As long as we already put some data to the top of the new logfile, subsequent writes should be performed with "append".
return true;
}
// The synchronous action is for renaming, here we want to hook
@Override public Action getSynchronous() {
Action delegateAction = delegate.getSynchronous();
if (delegateAction == null) return null;
return new MyAction(delegateAction, delegate.getActiveFileName());
}
// The asynchronous action is for compressing, we don't need to hook here
@Override public Action getAsynchronous() {
return delegate.getAsynchronous();
}
}
public RolloverDescription rollover(final RollingFileManager manager) {
RolloverDescription ret = super.rollover(manager);
return new MyRolloverDescription(ret);
}
}
如果我发布的feature request 能够实现，那么在 log4j2 的未来版本中解决这个要求可能会更容易。