前一篇博文介绍了JDK logging基础知识
博文中也提到LogManager，本章主要阐述怎么完全定制化LogManager来实现应用程序完全自定制的logger，其实对于大多数开发者来说，很少有需要定制LogManager的时候，只有是需要单独开发一个产品，需要完全独立的logger机制时才有可能需要定制LogManager，比如：
1，希望自由定制log的输出路径
2，希望完全定制log的format
3，希望日志中的国际化信息采用自己定义的一套机制等
当然，对于大型的中间件而言，自定义LogManager则是非常有必要的。
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 noJuli
set 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;
}
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();
}
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。
以上就是通过自定制LogManager实现程序完全自定义的logger的详细内容，更多关于自定制LogManager实现自定义logger的资料请关注编程网其它相关文章！
