自定义Log4j2的Appender

Appender是Log4j2的日志输出方式，Log4j2提供了很多自带的Appender，包括控制台的、文件的、邮件的，kafka的等等。

但是这样也是不能覆盖全部需求的，需要提供自定义的Appender。

 

考虑我们需要提供的Appender所需要的功能：

1、分析Perf4j的日志

2、将分析的日志按时间间隔输出到指定文件

 

提供自定义的Appender，需继承AbstractAppender类，实现append方法。

考虑继承FileAppender的实现将日志输出到指定的文件之中。 

GenericAsyncCoalescingStatisticsAppender 提供一个无参的构造方法，可以提供分析日志的功能。

 

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender;
import org.apache.logging.log4j.core.appender.FileManager;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
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.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.impl.Log4jLogEvent;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.core.net.Advertiser;
import org.apache.logging.log4j.core.util.Booleans;
import org.apache.logging.log4j.core.util.Integers;
import org.apache.logging.log4j.message.ObjectMessage;
import org.perf4j.GroupedTimingStatistics;
import org.perf4j.helpers.GenericAsyncCoalescingStatisticsAppender;
/**
 * 适配Perf4j的Appender
 * 
 * 解决目前Log4j2 没有提供支持Perf4j的Appender的问题
 * <p>
 * PerfjFileAppender提供类似{@link org.apache.logging.log4j.core.appender.FileAppender FileAppender}的实现
 *，并且内置Perfj的{@link org.perf4j.helpers.GenericAsyncCoalescingStatisticsAppender GenericAsyncCoalescingStatisticsAppender}对象
 * </p>
 * PerfjFileAppender的append方法，将日志信息提供到<code>GenericAsyncCoalescingStatisticsAppender</code>对象baseImplementation处理
 * 等到<code>GenericAsyncCoalescingStatisticsAppender</code>的silenceTime周期到了之后，就将<code>GenericAsyncCoalescingStatisticsAppender</code>
 * 的处理结果输出到PerfjFileAppender的父类<code>AbstractOutputStreamAppender</code>的append方法处理，该Appender将负责把统计结果输出到目标文件
 * 
 * <p>
 * <b>注意:</b>
 * <p>
 * 该实现中，始终会keep着第一次接收到的Perf4j的日志对象，
 * 并在每个输出的时机将GenericAsyncCoalescingStatisticsAppender输出的信息设置到日志对象，
 * 这就导致在应用启动之后，需要触发Perf4j才能输出信息，不然连空统计信息也不会输出
 * </p>
 * </p>
 * @author sunwei3
 * 
 */
@Plugin(name = "Perf4jAppender", category = "Core", elementType = "appender", printObject = true)
public class Perf4jFileAppender extends AbstractOutputStreamAppender<FileManager> {
    private final String fileName;
    private final Advertiser advertiser;
    private Object advertisement;
	private static final int DEFAULT_BUFFER_SIZE = 8192;
	private static final long serialVersionUID = 1L;
	private Log4jLogEvent result = null;
    private final GenericAsyncCoalescingStatisticsAppender baseImplementation =
    		new GenericAsyncCoalescingStatisticsAppender();
    
	protected Perf4jFileAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
            final FileManager manager, final String filename, final boolean ignoreExceptions,
            final boolean immediateFlush, final Advertiser advertiser,long timeSlice) {
		super(name, layout, filter, ignoreExceptions, immediateFlush, manager);
		baseImplementation.setTimeSlice(timeSlice);
		
        if (advertiser != null) {
            final Map<String, String> configuration = new HashMap<>(layout.getContentFormat());
            configuration.putAll(manager.getContentFormat());
            configuration.put("contentType", layout.getContentType());
            configuration.put("name", name);
            advertisement = advertiser.advertise(configuration);
        }
        this.fileName = filename;
        this.advertiser = advertiser;
		
		baseImplementation.start(new GenericAsyncCoalescingStatisticsAppender.GroupedTimingStatisticsHandler() {
            public void handle(GroupedTimingStatistics statistics) {
            	if(result == null)
            	{
            		return;
            	}
            	//已经处理完timeSlice时间段的数据，需要把统计结果输出到文件
            	fileAppend(result.asBuilder().setMessage(new ObjectMessage(statistics.toString())).build());
            }
            public void error(String errorMessage) {
                getHandler().error(errorMessage);
            }
        });
	}
	
	 @Override
	    public void stop() {
		 //先结束GenericAsyncCoalescingStatisticsAppender
		 	baseImplementation.stop();
	        super.stop();
	        if (advertiser != null) {
	            advertiser.unadvertise(advertisement);
	        }
	    }
	public void append(LogEvent event) {
		//仿照GenericAsyncCoalescingStatisticsAppender的实现，标准的Perf4j的输出是以start开头的
			if(result == null && String.valueOf(event.getMessage().getFormattedMessage()).startsWith("start")){
				//为了避免每次构造Log4jLogEvent，记录下第一次的Log4jLogEvent，每次设置其Message就可以输出到文件了
			result = new Log4jLogEvent.Builder(event).build();
			}
			//将日志交与GenericAsyncCoalescingStatisticsAppender处理，符合条件的日志将会被处理
			baseImplementation.append(String.valueOf(event.getMessage().getFormattedMessage()));
	}
	
	public void fileAppend(LogEvent event) {
		super.append(event);
	}
	
    public String getFileName() {
        return this.fileName;
    }
	@PluginFactory
	public static Perf4jFileAppender createAppender(
            // @formatter:off
            @PluginAttribute("fileName") final String fileName,
            @PluginAttribute("append") final String append,
            @PluginAttribute("locking") final String locking,
            @PluginAttribute("name") final String name,
            @PluginAttribute("immediateFlush") final String immediateFlush,
            @PluginAttribute("ignoreExceptions") final String ignore,
            @PluginAttribute("bufferedIo") final String bufferedIo,
            @PluginAttribute("bufferSize") final String bufferSizeStr,
            @PluginElement("Layout") Layout<? extends Serializable> layout,
            @PluginElement("Filter") final Filter filter,
            @PluginAttribute("advertise") final String advertise,
            @PluginAttribute("advertiseUri") final String advertiseUri,
            @PluginConfiguration final Configuration config,
            @PluginAttribute("timeSlice") final long timeSlice
			) {
        // @formatter:on
        final boolean isAppend = Booleans.parseBoolean(append, true);
        final boolean isLocking = Boolean.parseBoolean(locking);
        boolean isBuffered = Booleans.parseBoolean(bufferedIo, true);
        final boolean isAdvertise = Boolean.parseBoolean(advertise);
        if (isLocking && isBuffered) {
            if (bufferedIo != null) {
                LOGGER.warn("Locking and buffering are mutually exclusive. No buffering will occur for " + fileName);
            }
            isBuffered = false;
        }
        final int bufferSize = Integers.parseInt(bufferSizeStr, DEFAULT_BUFFER_SIZE);
        if (!isBuffered && bufferSize > 0) {
            LOGGER.warn("The bufferSize is set to {} but bufferedIO is not true: {}", bufferSize, bufferedIo);
        }
        final boolean isFlush = Booleans.parseBoolean(immediateFlush, true);
        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
        if (name == null) {
            LOGGER.error("No name provided for FileAppender");
            return null;
        }
        if (fileName == null) {
            LOGGER.error("No filename provided for FileAppender with name "  + name);
            return null;
        }
        if (layout == null) {
            layout = PatternLayout.createDefaultLayout();
        }
        final FileManager manager = FileManager.getFileManager(fileName, isAppend, isLocking, isBuffered, advertiseUri,
            layout, bufferSize);
        if (manager == null) {
            return null;
        }
        return new Perf4jFileAppender(name, layout, filter, manager, fileName, ignoreExceptions, isFlush,
                isAdvertise ? config.getAdvertiser() : null,timeSlice);
    }
}

　　log4j2的配置文件为：

<Perf4jAppender name="perfsStatistics" TimeSlice="1800000"
            fileName="${profile.log.root.path}/${profile.log.name.web}/perfStats.log">
            <PatternLayout>
                <Pattern>%m%n</Pattern>
            </PatternLayout>
</Perf4jAppender>