003-log-jul,jdk自带日志服务

一、简介

　　java官方日志jul，位于java.util.logging包下。

1.1、POM依赖

　　无依赖

1.2、配置

　　JUL的默认配置文件是logging.properties ,在 $JAVA_HOME/jre/lib下 (Mac 在 $JAVA_HOME/lib). 当然自己也可以修改文件位置,如:-Djava.util.logging.config.file=xxxpath/logging.properties

　　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

　　在tomcat的conf下就有个logging.properties,同时注意catalina.sh 里就有这样代码

# Set juli LogManager if it is present
if [ -r "$CATALINA_BASE"/conf/logging.properties ]; then
  JAVA_OPTS="$JAVA_OPTS -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager"
  LOGGING_CONFIG="-Djava.util.logging.config.file=$CATALINA_BASE/conf/logging.properties"
fi

1.3、使用

import java.util.logging.Level;
import java.util.logging.Logger;

public class ApplicationMain {
    private static Logger logger = Logger.getLogger(ApplicationMain.class.getName());

    public static void main(String[] args) {
        // 记录debug级别的信息
        logger.log(Level.INFO,"This is debug message.");
        // 记录info级别的信息
        logger.info("This is info message.");
        // 记录error级别的信息
        logger.warning("This is warning message.");
    }
}

二、详细说明

jul模块主要包含三个：Level、Formatter和Handler。

1.1、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);

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

1.2、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。

1.3、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。

1.4、简单示例

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");
    }
}

1.5、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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