java日志(二)–java官方日志jul的使用

一、简介

java官方日志jul，位于java.util.logging包下。

二、jul模块

jul模块主要包含三个：Level、Formatter和Handler。

2.1 Level

日志级别，由高到低有：OFF/SEVERE/WARNIN/INFO/CONFIG/FINE/FINERG/FINEST/ALL，
每个级别有自己的数值，在java.util.logging.Level类中源码如下：

public static final Level OFF = new Level("OFF",Integer.MAX_VALUE, defaultBundle);
public static final Level SEVERE = new Level("SEVERE",1000, defaultBundle);
public static final Level WARNING = new Level("WARNING", 900, defaultBundle);
public static final Level INFO = new Level("INFO", 800, defaultBundle);
public static final Level CONFIG = new Level("CONFIG", 700, defaultBundle);
public static final Level FINE = new Level("FINE", 500, defaultBundle);
public static final Level FINER = new Level("FINER", 400, defaultBundle);
public static final Level FINEST = new Level("FINEST", 300, defaultBundle);
public static final Level ALL = new Level("ALL", Integer.MIN_VALUE, defaultBundle);

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可自定义日志级别，继承java.util.logging.Level类即可。

2.2 Formatter

定义日志输出的格式，目前有SimpleFormatter和XMLFormatter两种格式，分别对应简单格式和xml格式。
可自定输出格式，继承抽象类java.util.logging.Formatter即可。

2.3 Handler

日志输出的目的，目前有
FileHandler：输出到文件，默认Level为INFO，Formatter为XMLFormatter；；
ConsoleHandler：输出到控制台，默认Level为INFO，流为System.err，Formatter为SimpleFormatter；
SocketHandler：输出到socket；
MemoryHandler：输出到内存；
可自定义日志级别，继承java.util.logging.Formatter类即可。

三、使用

jul关键类是java.util.logging.Logger,通过此类定义logger,相同logger名称只有一个实例。
如：Logger logger = Logger.getLogger(“javaLog”);
java.util.logging包下的类图如下：
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四、简单示例

这里直接通过代码，介绍Logger的使用，详情请查看注释。

import java.util.logging.*;

public class JavaLogStudyMain {
    public static void main(String[] args) throws Exception {
        //简单格式的Formatter
        SimpleFormatter sf = new SimpleFormatter();
        //xml格式的formatter
        XMLFormatter xf = new XMLFormatter();

        //输出到文件的hander,指定日志输出级别为ALL
        FileHandler fh = new FileHandler("jul_study.log");
        fh.setLevel(Level.ALL);
        fh.setFormatter(sf);
//        fh.setFormatter(xf);

        //输出到控制台的handler,指定日志输出级别为INFO
        ConsoleHandler ch = new ConsoleHandler();
        ch.setLevel(Level.INFO);

        //获取logger实例，相同名的只能生成一个实例
        Logger logger = Logger.getLogger("javaLog");
        logger.addHandler(fh);   //添加输出handler
        logger.addHandler(ch);   //添加输出handler
        logger.setLevel(Level.ALL);  //指定logger日志级别

        //日志输出简写形式，有不同的级别，可带参数，其它类似
        logger.log(Level.INFO, "this is a info, {0}", "p1");
        logger.log(Level.WARNING, "this is a warn, {0} {1}", new Object[]{"p1", "p2"});
        logger.log(Level.SEVERE, "this is a severe");
        logger.log(Level.FINE, "this is a fine");
        logger.log(Level.FINEST, "this is a finest");
        logger.log(Level.CONFIG, "this is a config");
        logger.log(Level.INFO, "this is a info", new Exception("my excep")); //带异常输出

        //日志输出简写形式，有不同的级别
        logger.severe("severe log");
        logger.warning("warning log");
        logger.info("info log");
        logger.config("config log");
        logger.fine("fine log");
        logger.finer("finer log");
        logger.finest("finest log");
    }
}

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四、自定义logger
这里通过继承Level、Handler、Formatter自定义Logger，日志存在文件中，且每个不同的loggerName存不同日志文件中。
示例如下，解释请查看注释：

import org.apache.commons.lang.time.DateFormatUtils;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.logging.*;

public class SelfJavaLogMain {
    //生成单例日志输出handler实例
    private static SelfHandle sf = new SelfHandle();

    /**
     * 根据class获取logger
     * @param clazz
     * @return
     */
    public static Logger getLogger(Class clazz){
        return getLogger(clazz.getSimpleName());
    }

    /**
     * 根据loggerName获取logger
     * @param loggerName
     * @return
     */
    public static Logger getLogger(String loggerName){
        Logger logger = Logger.getLogger(loggerName);
        logger.addHandler(sf);
        return logger;
    }

    /**
     * 自定义日志格式formatter
     */
    public static class SelfFormater extends Formatter {

        public static SelfFormater selfFormater = new SelfFormater();

        @Override
        public String format(LogRecord record) {
            return String.format("[%s] %s %s.%s: %s\r\n", DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss"),
                    record.getLevel().getName(), record.getSourceClassName(), record.getSourceMethodName(), record.getMessage());
        }

        public static SelfFormater getInstance() {
            return selfFormater;
        }
    }

    /**
     * 自定义日志level
     */
    public static class SelfLevel extends Level {

        public static SelfLevel ERROR = new SelfLevel("ERROR", 910);

        /**
         * @param name  自定义级别名称
         * @param value 自定义级别的权重值
         */
        protected SelfLevel(String name, int value) {
            super(name, value);
        }
    }

    /**
     * 自定义日志输出handler
     */
    public static class SelfHandle extends Handler {

        /**
         * 日志写入的位置
         *
         * @param record
         */
        @Override
        public void publish(LogRecord record) {
            try {
                //每一个不同的loggerName分别记在不同的日志文件中
                File file = new File(String.format("%s_%s.log",record.getLoggerName(), DateFormatUtils.format(new Date(),"yyyy-MM-dd")));
                if(!file.exists()){
                    file.createNewFile();
                }
                FileWriter fw = new FileWriter(file,true);
                PrintWriter pw = new PrintWriter(fw);
                String log = String.format("[%s] %s %s.%s: %s\r\n", DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss"),
                        record.getLevel().getName(), record.getSourceClassName(), record.getSourceMethodName(), record.getMessage());
                pw.write(log);
                pw.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

        /**
         * 刷新缓存区，保存数据
         */
        @Override
        public void flush() {
        }

        /**
         * 关闭
         *
         * @throws SecurityException
         */
        @Override
        public void close() throws SecurityException {
        }
    }

    public static void main(String[] args) throws Exception {
        //获取自定义的logger
        Logger logger = getLogger(SelfJavaLogMain.class);
        logger.info("info log");
        logger.severe("severe log");
        //使用自定义的logger level
        logger.log(SelfLevel.ERROR, "error log");
    }
}

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五、jre日志默认配置

jre(java runtime environment, 即java运行环境)的默认日志配置为jre/lib/logging.properties，
其配置如下：

\############################################################
\#    Default Logging Configuration File
\#
\# You can use a different file by specifying a filename
\# with the java.util.logging.config.file system property.  
\# For example java -Djava.util.logging.config.file=myfile
\############################################################

\############################################################
\#    Global properties
\############################################################

\# "handlers" specifies a comma separated list of log Handler 
\# classes.  These handlers will be installed during VM startup.
\# Note that these classes must be on the system classpath.
\# By default we only configure a ConsoleHandler, which will only
\# show messages at the INFO and above levels.
handlers= java.util.logging.ConsoleHandler

\# To also add the FileHandler, use the following line instead.
\#handlers= java.util.logging.FileHandler, java.util.logging.ConsoleHandler

\# Default global logging level.
\# This specifies which kinds of events are logged across
\# all loggers.  For any given facility this global level
\# can be overriden by a facility specific level
\# Note that the ConsoleHandler also has a separate level
\# setting to limit messages printed to the console.
.level= INFO

\############################################################
\# Handler specific properties.
\# Describes specific configuration info for Handlers.
\############################################################

\# default file output is in user's home directory.
java.util.logging.FileHandler.pattern = %h/java%u.log
java.util.logging.FileHandler.limit = 50000
java.util.logging.FileHandler.count = 1
java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

\# Limit the message that are printed on the console to INFO and above.
java.util.logging.ConsoleHandler.level = INFO
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

\# Example to customize the SimpleFormatter output format 
\# to print one-line log message like this:
\#   <level>: <log message> [<date/time>]
\#
\# java.util.logging.SimpleFormatter.format=%4$s: %5$s [%1$tc]%n

\############################################################
\# Facility specific properties.
\# Provides extra control for each logger.
\############################################################

\# For example, set the com.xyz.foo logger to only log SEVERE
\# messages:
com.xyz.foo.level = SEVERE