怎么自定制LogManager实现程序完全自定义的logger

本篇内容主要讲解"怎么自定制LogManager实现程序完全自定义的logger"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"怎么自定制LogManager实现程序完全自定义的logger"吧!

引言

对tomcat熟悉的读者，有可能会注意到tomcat的启动脚本catalina.bat中也使用定制的LogManager，如下：

if not exist "%CATALINA_HOME%\bin\tomcat-juli.jar" goto noJuliset JAVA_OPTS=%JAVA_OPTS% -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file="%CATALINA_BASE%\conf\logging.properties"

当tomcat的bin路径下存在tomcat-juli.jar文件(也就是存在定制的LogManager)时，那么会强制在JVM系统属性中指定org.apache.juli.ClassLoaderLogManager作为整个JVM的LogManager，以此来完成一些特殊操作。

websphere的启动脚本startServer.bat中也定义了自己的LogManager，如下：

java.util.logging.manager=com.ibm.ws.bootstrap.WsLogManager

怎么实现自定义的LogManager

首先要实现一个继承自java.util.logging.LogManager的类：

子类覆盖java.util.logging.LogManager的addLogger方法，在成功添加logger之后对logger做定制化操作，从代码中可以看出addLogger方法调用了子类的internalInitializeLogger方法，internalInitializeLogger方法中先清空logger的所有handler，然后再增加一个自定义的Handler

需要说明一下：internalInitializeLogger方法中的操作(给logger增设我们自定义的handler)是我们自定义LogManager的一大目的。

package com.bes.logging;import java.util.logging.Handler;import java.util.logging.Level;import java.util.logging.LogManager;import java.util.logging.Logger;public class ServerLogManager extends LogManager {        private static ServerFileHandler handlerSingleton;        private static ServerLogManager thisInstance;        private Object lockObj = new Object();        public ServerLogManager() {                super();        }        public static synchronized ServerLogManager getInstance() {                if (thisInstance == null) {                        thisInstance = new ServerLogManager();                }                return thisInstance;        }        public boolean addLogger(Logger logger) {                boolean result = super.addLogger(logger);                 //initialize Logger                if (logger.getResourceBundleName() == null) {                        try {                                Logger newLogger = Logger.getLogger(logger.getName(),                                                getLoggerResourceBundleName(logger.getName()));                                assert (logger == newLogger);                        } catch (Throwable ex) {                                //ex.printStackTrace();                        }                }                synchronized (lockObj) {                        internalInitializeLogger(logger);                }                return result;        }        /**         * Internal Method to initialize a list of unitialized loggers.         */        private void internalInitializeLogger(final Logger logger) {                // Explicitly remove all handlers.                Handler[] h = logger.getHandlers();                for (int i = 0; i < h.length; i++) {                        logger.removeHandler(h[i]);                }                logger.addHandler(getServerFileHandler());                logger.setUseParentHandlers(false);                logger.setLevel(Level.FINEST);// only for test        }        private static synchronized Handler getServerFileHandler() {                if (handlerSingleton == null) {                        try {                                handlerSingleton = ServerFileHandler.getInstance();                                handlerSingleton.setLevel(Level.ALL);                        } catch (Exception e) {                                e.printStackTrace();                        }                }                return handlerSingleton;        }        public String getLoggerResourceBundleName(String loggerName) {                String result = loggerName + "." + "LogStrings";                return result;        }}

自定义的LogManager中使用到的ServerFileHandler

如下：

该ServerFileHandler是一个把logger日志输出到文件中的handler，可以通过com.bes.instanceRoot系统属性来指定日志文件跟路径；其次，ServerFileHandler也指定了自己的UniformLogFormatter；最后是需要覆盖父类的publish方法，覆盖的publish方法在做真正的日志输入之前会检查日志文件是否存在，然后就是创建一个和日志文件对应的输出流，把该输出流设置为ServerFileHandler的输出流以至日志输出的时候能输出到文件中。另外，WrapperStream仅仅是一个流包装类。

这里也需要说一下：ServerFileHandler构造方法中的setFormatter(new UniformLogFormatter());操作是我们自定义LogManager的第二大目的。

package com.bes.logging;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.OutputStream;import java.util.logging.LogRecord;import java.util.logging.StreamHandler;public class ServerFileHandler extends StreamHandler {  private WrapperStream wrappedStream;  private String absoluteFileName = null;  static final String LOG_FILENAME_PREFIX = "server";  static final String LOG_FILENAME_SUFFIX = ".log";  private String logFileName = LOG_FILENAME_PREFIX + LOG_FILENAME_SUFFIX;  public static final ServerFileHandler thisInstance = new ServerFileHandler();  public static synchronized ServerFileHandler getInstance() {    return thisInstance;  }  protected ServerFileHandler() {    try {      setFormatter(new UniformLogFormatter());    } catch (Exception e) {      e.printStackTrace();    }  }  public synchronized void publish(LogRecord record) {    if (wrappedStream == null) {      try {        absoluteFileName = createFileName();        openFile(absoluteFileName);      } catch (Exception e) {        throw new RuntimeException(            "Serious Error Couldn't open Log File" + e);      }    }    super.publish(record);    flush();  }  public String createFileName() {    String instDir = "";    instDir = System.getProperty("com.bes.instanceRoot");    if(instDir == null || "".equals(instDir)){      instDir = ".";    }    return instDir + "/" + getLogFileName();  }  /**   * Creates the file and initialized WrapperStream and passes it on to   * Superclass (java.util.logging.StreamHandler).   */  private void openFile(String fileName) throws IOException {    File file = new File(fileName);    if(!file.exists()){      if(file.getParentFile() != null && !file.getParentFile().exists()){        file.getParentFile().mkdir();      }      file.createNewFile();    }    FileOutputStream fout = new FileOutputStream(fileName, true);    BufferedOutputStream bout = new BufferedOutputStream(fout);    wrappedStream = new WrapperStream(bout, file.length());    setOutputStream(wrappedStream);  }  private class WrapperStream extends OutputStream {    OutputStream out;    long written;    WrapperStream(OutputStream out, long written) {      this.out = out;      this.written = written;    }    public void write(int b) throws IOException {      out.write(b);      written++;    }    public void write(byte buff[]) throws IOException {      out.write(buff);      written += buff.length;    }    public void write(byte buff[], int off, int len) throws IOException {      out.write(buff, off, len);      written += len;    }    public void flush() throws IOException {      out.flush();    }    public void close() throws IOException {      out.close();    }  }  protected String getLogFileName() {    return logFileName;  }}

实现Formatter

之前已经提到过，使用logger日志输出的时候，handler会自动调用自己的formatter对日志做format，然后输出格式化之后的日志。自定义的Formatter只需要覆盖public String format(LogRecord record)便可。这个类本身很简单，就是日志输出时自动增加指定格式的时间，加上分隔符，对日志进行国际化处理等操作。 需要注意的是类中对ResourceBundle做了缓存以提高效率。

package com.bes.logging;import java.text.MessageFormat;import java.text.SimpleDateFormat;import java.util.Date;import java.util.HashMap;import java.util.ResourceBundle;import java.util.logging.Formatter;import java.util.logging.LogManager;import java.util.logging.LogRecord;public class UniformLogFormatter extends Formatter {  private Date date = new Date();  private HashMap loggerResourceBundleTable;  private LogManager logManager;  private static final char FIELD_SEPARATOR = '|';  private static final String CRLF = System.getProperty("line.separator");  private static final SimpleDateFormat dateFormatter = new SimpleDateFormat(      "yyyy-MM-dd'T'HH:mm:ss.SSSZ");  public UniformLogFormatter() {    super();    loggerResourceBundleTable = new HashMap();    logManager = LogManager.getLogManager();  }  public String format(LogRecord record) {    return uniformLogFormat(record);  }  private String uniformLogFormat(LogRecord record) {    try {      String logMessage = record.getMessage();      int msgLength = 150; // typical length of log record      if (logMessage != null)        msgLength += logMessage.length();      StringBuilder recordBuffer = new StringBuilder(msgLength);      // add date to log      date.setTime(record.getMillis());      recordBuffer.append(dateFormatter.format(date)).append(          FIELD_SEPARATOR);      // add log level and logger name to log      recordBuffer.append(record.getLevel()).append(FIELD_SEPARATOR);      recordBuffer.append(record.getLoggerName()).append(FIELD_SEPARATOR);      if (logMessage == null) {        logMessage = "The log message is null.";      }      if (logMessage.indexOf("{0}") >= 0) {        try {          logMessage = java.text.MessageFormat.format(logMessage,              record.getParameters());        } catch (Exception e) {          // e.printStackTrace();        }      } else {        ResourceBundle rb = getResourceBundle(record.getLoggerName());        if (rb != null) {          try {            logMessage = MessageFormat.format(                rb.getString(logMessage),                record.getParameters());          } catch (java.util.MissingResourceException e) {          }        }      }      recordBuffer.append(logMessage);      recordBuffer.append(CRLF);      return recordBuffer.toString();    } catch (Exception ex) {      return "Log error occurred on msg: " + record.getMessage() + ": "          + ex;    }  }  private synchronized ResourceBundle getResourceBundle(String loggerName) {    if (loggerName == null) {      return null;    }    ResourceBundle rb = (ResourceBundle) loggerResourceBundleTable        .get(loggerName);    if (rb == null) {      rb = logManager.getLogger(loggerName).getResourceBundle();      loggerResourceBundleTable.put(loggerName, rb);    }    return rb;  }}

完成了定制的LogManager之后，在启动JVM的命令中增加系统属性便可

java -Djava.util.logging.manager=com.bes.logging.ServerLogManager

加上这个系统属性之后通过java.util.logging.Logger类获取的logger都是经过定制的LogManager作为初始化的，日志输出的时候便会使用上面的ServerFileHandler#publish()方法进行日志输出，并使用UniformLogFormatter对日志进行格式化。

到此，相信大家对"怎么自定制LogManager实现程序完全自定义的logger"有了更深的了解，不妨来实际操作一番吧！这里是网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！