Aquí hay una implementación simple de un registrador sincronizado utilizando el FileChannel java nio. En este ejemplo, los mensajes de registro están limitados a 1024 bytes. Puede ajustar la longitud del mensaje de registro cambiando el valor BUFFER_SIZE.
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.HashMap;
/**
* The MyLogger class abstracts the writing of log messages to a file.
* This is a synchronized implementation due to the usage of java.nio.channels.FileChannel
* which is used to write log messages to the log file.
*
* The MyLogger class maintains a HashMap of MyLogger instances per log file.
* The Key is the MD5 hash of the log file path and the Value is the MyLogger instance for that log file.
*
*/
public final class MyLogger {
private static final int BUFFER_SIZE = 1024;
private static final int DIGEST_BASE_RADIX = 16;
private static final String LINE_SEPARATOR = System.getProperty("line.separator");
private static HashMap<String, MyLogger> sLoggerMap;
private FileChannel mLogOutputChannel;
private ByteBuffer mByteBuffer;
private String mLogDir;
private String mLogFileName;
/**
* Private constructor which creates our log dir and log file if they do not already already exist.
* If the log file exists, then it is opened in append mode.
*
* @param logDir
* The dir where the log file resides
* @param logFileName
* The file name of the log file
* @throws IOException
* Thrown if the file could not be created or opened for writing.
*/
private MyLogger(String logDir, String logFileName) throws IOException {
mLogDir = logDir;
mLogFileName = logFileName;
// create the log dir and log file if they do not exist
FileOutputStream logFile;
new File(mLogDir).mkdirs();
final String logFilePath = mLogDir + File.separatorChar + mLogFileName;
final File f = new File(logFilePath);
if(!f.exists()) {
f.createNewFile();
}
logFile = new FileOutputStream(logFilePath, true);
// set up our output channel and byte buffer
mLogOutputChannel = logFile.getChannel();
mByteBuffer = ByteBuffer.allocate(BUFFER_SIZE);
}
/**
* Writes the given log message to the log file that is represented by this MyLogger instance.
* If the log message could not be written to the log file an error is logged in the System log.
*
* @param logMessage
* The log message to write to the log file.
*/
public void log(String logMessage) {
// write the log message to the log file
if (mLogOutputChannel != null) {
mByteBuffer.put(logMessage.getBytes());
mByteBuffer.put(LINE_SEPARATOR.getBytes());
mByteBuffer.flip();
try {
mLogOutputChannel.write(mByteBuffer);
// ensure that the data we just wrote to the log file is pushed to the disk right away
mLogOutputChannel.force(true);
} catch (IOException e) {
// Could not write to log file output channel
e.printStackTrace();
return;
}
}
if(mByteBuffer != null) {
mByteBuffer.clear();
}
}
/**
* Get an instance of the MyLogger for the given log file. Passing in the same logDir and logFileName will result in the same MyLogger instance being returned.
*
* @param logDir
* The directory path where the log file resides. Cannot be empty or null.
* @param logFileName
* The name of the log file Cannot be empty or null.
* @return The instance of the MyLogger representing the given log file. Null is returned if either logDir or logFilename is null or empty string.
* @throws IOException
* Thrown if the file could not be created or opened for writing.
*/
public static MyLogger getLog(String logDir, String logFileName) throws IOException {
if(logDir == null || logFileName == null || logDir.isEmpty() || logFileName.isEmpty()) {
return null;
}
if(sLoggerMap == null) {
sLoggerMap = new HashMap<String, MyLogger>();
}
final String logFilePathHash = getHash(logDir + File.separatorChar + logFileName);
if(!sLoggerMap.containsKey(logFilePathHash)) {
sLoggerMap.put(logFilePathHash, new MyLogger(logDir, logFileName));
}
return sLoggerMap.get(logFilePathHash);
}
/**
* Utility method for generating an MD5 hash from the given string.
*
* @param path
* The file path to our log file
* @return An MD5 hash of the log file path. If an MD5 hash could not be generated, the path string is returned.
*/
private static String getHash(String path) {
try {
final MessageDigest digest = MessageDigest.getInstance("MD5");
digest.update(path.getBytes());
return new BigInteger(digest.digest()).toString(DIGEST_BASE_RADIX);
} catch (NoSuchAlgorithmException ex) {
// this should never happen, but just to make sure return the path string
return path;
}
}
}
Esta es la forma en que lo utilizaría:
MyLogger aLogger = MyLogger.getLog("/path/to/log/dir", "logFilename");
aLogger.log("my log message");
es posible que desee buscar en [FileChannel] (http://docs.oracle.com/javase/6/docs/api/java /nio/channels/FileChannel.html) – Nerdtron
Respondo en segundo lugar la respuesta de Nerdtron. La solución Java nio FileChannel es, de lejos, la más simple de implementar. –