log4j日志扩展---自定义PatternLayout

目前扩展log4j的日志一般使用扩展adaper的方法,这里使用一种扩展PatternLayout方法.

log4j.rootLogger=debug, stdout, R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=example.log

log4j.appender.R.MaxFileSize=100KB
# Keep one backup file
log4j.appender.R.MaxBackupIndex=1

log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

这是log4j官网上的配置

请注意:

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.R.layout=org.apache.log4j.PatternLayout

注意到其实这是两个类

那么org.apache.log4j.ConsoleAppender可以自定义,思考是否可以自定义log4j.appender.R.layout=org.apache.log4j.PatternLayout

下载官方文件发现有这样两个类.

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0 *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package examples;

import org.apache.log4j.*;
import org.apache.log4j.helpers.PatternParser;

/**

Example showing how to extend PatternLayout to recognize additional
conversion characters.

<p>In this case MyPatternLayout recognizes %# conversion pattern. It
outputs the value of an internal counter which is also incremented
at each call.

<p>See <a href=doc-files/MyPatternLayout.java><b>source</b></a> code
for more details.

@see MyPatternParser
@see org.apache.log4j.PatternLayout
@author Anders Kristensen
*/
public class MyPatternLayout extends PatternLayout {
public
MyPatternLayout() {
this(DEFAULT_CONVERSION_PATTERN);
}

public
MyPatternLayout(String pattern) {
super(pattern);
}

public
PatternParser createPatternParser(String pattern) {
return new MyPatternParser(
pattern == null ? DEFAULT_CONVERSION_PATTERN : pattern);
}

public
static void main(String[] args) {
Layout layout = new MyPatternLayout("[counter=%.10#] - %m%n");
Logger logger = Logger.getLogger("some.cat");
logger.addAppender(new ConsoleAppender(layout, ConsoleAppender.SYSTEM_OUT));
logger.debug("Hello, log");
logger.info("Hello again...");
}
}
 

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0 *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package examples;

import org.apache.log4j.helpers.FormattingInfo;
import org.apache.log4j.helpers.PatternConverter;
import org.apache.log4j.helpers.PatternParser;
import org.apache.log4j.spi.LoggingEvent;

/**
Example showing how to extend PatternParser to recognize additional
conversion characters.  The examples shows that minimum and maximum
width and alignment settings apply for "extension" conversion
characters just as they do for PatternLayout recognized characters.

<p>In this case MyPatternParser recognizes %# and outputs the value
of an internal counter which is also incremented at each call.

See <a href=doc-files/MyPatternParser.java><b>source</b></a> code
for more details.

@see org.apache.log4j.examples.MyPatternLayout
@see org.apache.log4j.helpers.PatternParser
@see org.apache.log4j.PatternLayout

@author Anders Kristensen
*/
public class MyPatternParser extends PatternParser {

int counter = 0;

public
MyPatternParser(String pattern) {
super(pattern);
}

public
void finalizeConverter(char c) {
if (c == '#') {
addConverter(new UserDirPatternConverter(formattingInfo));
currentLiteral.setLength(0);
} else {
super.finalizeConverter(c);
}
}

private class UserDirPatternConverter extends PatternConverter {
UserDirPatternConverter(FormattingInfo formattingInfo) {
super(formattingInfo);
}

public
String convert(LoggingEvent event) {
return String.valueOf(++counter);
}
}
}

直接粘过去找个类测试一下发现是可以使用的,显示打印日志的行数

发现MyPatternLayout基本调用的是父类的方法

继续扒

public
void finalizeConverter(char c) {
if (c == '#') {
addConverter(new UserDirPatternConverter(formattingInfo));
currentLiteral.setLength(0);
} else {
super.finalizeConverter(c);
}
}

注意看这段代码

发现字符为"#"的时候,创建了UserDirPatternConverter

推荐大家去看PatternParser这里面有答案

给大家举个例子

%#{MMMM}

使用extractOption()可以获得MMMM

有了MMMM是不是就可以处理很多问题.

想一下,比如我们要在日志里面打印公司的编号  orgId

那么首先配置

log4j.appender.R.layout.ConversionPattern= %#{orgId}  %p %t %c - %m%n

这样的话

if (c == '#') {
String exs = super.extractOption();  //获取orgId
addConverter(new ExrPatternConverter(formattingInfo, exs));
currentLiteral.setLength(0);

} else {
super.finalizeConverter(c);
}

考虑orgId的赋值问题

使用ThreadLocal

故完整的代码

package com.yogapay.core;

import java.util.HashMap;
import java.util.Map;

import org.apache.log4j.helpers.FormattingInfo;
import org.apache.log4j.helpers.PatternConverter;
import org.apache.log4j.helpers.PatternParser;
import org.apache.log4j.spi.LoggingEvent;

public class ExPatternParser extends PatternParser {

static final ThreadLocal<Map<String, Object>> TH_LOCAL = new ThreadLocal<Map<String, Object>>(){
@Override
protected HashMap<String, Object> initialValue() {
return new HashMap<String, Object>();
}
};

public static void setCurrentValue(String key, Object value) {
Map<String, Object> map = TH_LOCAL.get();
map.put(key, value);

}

public ExPatternParser(String pattern) {
super(pattern);
}

public void finalizeConverter(char c) {
if (c == '#') {
String exs = super.extractOption();
addConverter(new ExrPatternConverter(formattingInfo, exs));
currentLiteral.setLength(0);

} else {
super.finalizeConverter(c);
}
}

private class ExrPatternConverter extends PatternConverter {

private String cfg;

ExrPatternConverter(FormattingInfo formattingInfo, String cfg) {
super(formattingInfo);
this.cfg = cfg;
}

public String convert(LoggingEvent event) {
Map<String, Object> valueMap = TH_LOCAL.get();
if (valueMap != null) {
Object value = valueMap.get(cfg);
if (value != null) {
return String.valueOf(value);
}
}
return "";
}
}
}

package com.yogapay.core;

import org.apache.log4j.*;
import org.apache.log4j.helpers.PatternParser;

public class ExPatternLayout extends PatternLayout {
public ExPatternLayout() {
this(DEFAULT_CONVERSION_PATTERN);
}

public ExPatternLayout(String pattern) {
super(pattern);
}

@Override
public PatternParser createPatternParser(String pattern) {
return new ExPatternParser(pattern == null ? DEFAULT_CONVERSION_PATTERN : pattern);
}
}

### set log levels ###
log4j.rootLogger = info,stdout

### 输出到控制台 ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = com.yogapay.core.ExPatternLayout
log4j.appender.stdout.layout.ConversionPattern = lgcNo:%#{orgId} %d{yyyy-MM-dd HH:mm:ss} [%t] %p [%c] - %m%n

到此扩展就完成呢!

a9ef