java - LOG4J:使用自定义附加程序修改记录的消息

Question

出于安全原因，我需要查看我的应用程序中的每条记录消息，并可能在将其转到日志文件之前对其进行修改。我想我可以编写一个自定义附加程序(扩展 DailyRollingFileAppender)并覆盖 subAppend(LoggingEvent 事件)。问题是，LoggingEvent 中的消息文本没有 setter ，消息是私有(private)属性。我可以用我修改过的消息创建一个新的 LoggingEvent，但是 API 不容易复制原始 LoggingEvent 的其余部分。这一切似乎都是为了阻止在自定义附加程序中干预消息。

我能看到的唯一其他选项是修改数百个日志记录语句以调用一个新的全局方法，该方法可以先修改文本然后进行 Log4J 调用。我宁愿不要!

有没有其他人需要修改自定义附加程序中记录的消息？

Answer 1

我不完全确定为什么创建一个新的 LoggingEvent 如此繁重。这似乎对我有用:

package test.logging;

import org.apache.log4j.DailyRollingFileAppender;
import org.apache.log4j.spi.LoggingEvent;

public class MyDailyRollingFileAppender extends DailyRollingFileAppender {

    @Override
    protected void subAppend(LoggingEvent event) {
        String modifiedMessage = String.format("**** Message modified by MyDailyRollingFileAppender ****\n\n%s\n\n**** Finished modified message ****", event.getMessage());
        LoggingEvent modifiedEvent = new LoggingEvent(event.getFQNOfLoggerClass(), event.getLogger(), event.getTimeStamp(), event.getLevel(), modifiedMessage,
                                                      event.getThreadName(), event.getThrowableInformation(), event.getNDC(), event.getLocationInformation(),
                                                      event.getProperties());

        super.subAppend(modifiedEvent);
    }

}

通过这个测试:

package test;

import org.apache.log4j.Logger;

public class TestLogging {

    public static void main(String[] args) {
        Logger log = Logger.getLogger(TestLogging.class);
        log.info("I am testing my logging");
        log.info("Here is an exception", new Exception());
    }

}

和这个配置:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

    <appender name="MyDailyRollingFileAppender" class="test.logging.MyDailyRollingFileAppender">
        <param name="Append" value="true"/>
        <param name="datePattern" value="'.'yyyy-MM-dd"/>
        <param name="File" value="mine.log"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d %-5p (%x) [%t] %c{1} - %m%n" />
        </layout>
    </appender>

    <root>
        <priority value="debug"/>
        <appender-ref ref="MyDailyRollingFileAppender"/>
    </root>

</log4j:configuration>

我得到以下输出:

2011-10-14 10:09:09,322 INFO  () [main] TestLogging - **** Message modified by MyDailyRollingFileAppender ****

I am testing my logging

**** Finished modified message ****
2011-10-14 10:09:09,333 INFO  () [main] TestLogging - **** Message modified by MyDailyRollingFileAppender ****

Here is an exception

**** Finished modified message ****
java.lang.Exception
    at test.TestLogging.main(TestLogging.java:10)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

虽然我也做过类似的事情，但我使用的方法略有不同。我没有编写我想使用的每种类型的 Appender 的子类，而是创建了一个 Appender 来包装其他 Appender 对象，并在之前修改消息发送到包装的 Appender。像这样:

package test.logging;

import org.apache.log4j.Appender;
import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.spi.AppenderAttachable;
import org.apache.log4j.spi.LoggingEvent;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;

public class MyAppenderWrapper extends AppenderSkeleton implements AppenderAttachable {

    private final List<Appender> appenders = new ArrayList<Appender>();

    public void close() {
        synchronized (appenders) {
            for (Appender appender : appenders) {
                appender.close();
            }
        }
    }

    public boolean requiresLayout() {
        return false;
    }

    public void addAppender(Appender appender) {
        synchronized (appenders) {
            appenders.add(appender);
        }
    }

    public Enumeration getAllAppenders() {
        return Collections.enumeration(appenders);
    }

    public Appender getAppender(String name) {
        synchronized (appenders) {
            for (Appender appender : appenders) {
                if (appender.getName().equals(name)) {
                    return appender;
                }
            }
        }
        return null;
    }

    public boolean isAttached(Appender appender) {
        synchronized (appenders) {
            for (Appender wrapped : appenders) {
                if (wrapped.equals(appender)) {
                    return true;
                }
            }
            return false;
        }
    }

    public void removeAllAppenders() {
        synchronized (appenders) {
            appenders.clear();
        }
    }

    public void removeAppender(Appender appender) {
        synchronized (appenders) {
            for (Iterator<Appender> i = appenders.iterator(); i.hasNext(); ) {
                if (i.next().equals(appender)) {
                    i.remove();
                }
            }
        }
    }

    public void removeAppender(String name) {
        synchronized (appenders) {
            for (Iterator<Appender> i = appenders.iterator(); i.hasNext(); ) {
                if (i.next().getName().equals(name)) {
                    i.remove();
                }
            }
        }
    }

    @Override
    protected void append(LoggingEvent event) {
        String modifiedMessage = String.format("**** Message modified by MyAppenderWrapper ****\n\n%s\n\n**** Finished modified message ****", event.getMessage());
        LoggingEvent modifiedEvent = new LoggingEvent(event.getFQNOfLoggerClass(), event.getLogger(), event.getTimeStamp(), event.getLevel(), modifiedMessage,
                                                      event.getThreadName(), event.getThrowableInformation(), event.getNDC(), event.getLocationInformation(),
                                                      event.getProperties());

        synchronized (appenders) {
            for (Appender appender : appenders) {
                appender.doAppend(modifiedEvent);
            }
        }
    }

}

你可以这样配置:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

    <appender name="StdOut" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d %-5p (%x) [%t] %c{1} - %m%n" />
        </layout>
    </appender>

    <appender name="FileAppender" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="Append" value="true"/>
        <param name="datePattern" value="'.'yyyy-MM-dd"/>
        <param name="File" value="mine.log"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d %-5p (%x) [%t] %c{1} - %m%n" />
        </layout>
    </appender>

    <appender name="AppenderWrapper" class="test.logging.MyAppenderWrapper">
        <appender-ref ref="StdOut"/>
        <appender-ref ref="FileAppender"/>
    </appender>

    <root>
        <priority value="debug"/>
        <appender-ref ref="AppenderWrapper"/>
    </root>

</log4j:configuration>

这样，消息仍会发送到原始附加程序，但带有修改后的消息。