Java example source code file (FileHandler.java)
The FileHandler.java Java example source code/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.util.logging;
import static java.nio.file.StandardOpenOption.CREATE_NEW;
import static java.nio.file.StandardOpenOption.WRITE;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.channels.FileChannel;
import java.nio.file.FileAlreadyExistsException;
import java.nio.file.Paths;
import java.security.AccessController;
import java.security.PrivilegedAction;
/**
* Simple file logging <tt>Handler.
* <p>
* The <tt>FileHandler can either write to a specified file,
* or it can write to a rotating set of files.
* <p>
* For a rotating set of files, as each file reaches a given size
* limit, it is closed, rotated out, and a new file opened.
* Successively older files are named by adding "0", "1", "2",
* etc. into the base filename.
* <p>
* By default buffering is enabled in the IO libraries but each log
* record is flushed out when it is complete.
* <p>
* By default the <tt>XMLFormatter class is used for formatting.
* <p>
* <b>Configuration:
* By default each <tt>FileHandler is initialized using the following
* <tt>LogManager configuration properties where <handler-name>
* refers to the fully-qualified class name of the handler.
* If properties are not defined
* (or have invalid values) then the specified default values are used.
* <ul>
* <li> <handler-name>.level
* specifies the default level for the <tt>Handler
* (defaults to <tt>Level.ALL).
* <li> <handler-name>.filter
* specifies the name of a <tt>Filter class to use
* (defaults to no <tt>Filter).
* <li> <handler-name>.formatter
* specifies the name of a <tt>Formatter class to use
* (defaults to <tt>java.util.logging.XMLFormatter)
* <li> <handler-name>.encoding
* the name of the character set encoding to use (defaults to
* the default platform encoding). </li>
* <li> <handler-name>.limit
* specifies an approximate maximum amount to write (in bytes)
* to any one file. If this is zero, then there is no limit.
* (Defaults to no limit). </li>
* <li> <handler-name>.count
* specifies how many output files to cycle through (defaults to 1). </li>
* <li> <handler-name>.pattern
* specifies a pattern for generating the output file name. See
* below for details. (Defaults to "%h/java%u.log"). </li>
* <li> <handler-name>.append
* specifies whether the FileHandler should append onto
* any existing files (defaults to false). </li>
* </ul>
* <p>
* For example, the properties for {@code FileHandler} would be:
* <ul>
* <li> java.util.logging.FileHandler.level=INFO
* <li> java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter
* </ul>
* <p>
* For a custom handler, e.g. com.foo.MyHandler, the properties would be:
* <ul>
* <li> com.foo.MyHandler.level=INFO
* <li> com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter
* </ul>
* <p>
* A pattern consists of a string that includes the following special
* components that will be replaced at runtime:
* <ul>
* <li> "/" the local pathname separator
* <li> "%t" the system temporary directory
* <li> "%h" the value of the "user.home" system property
* <li> "%g" the generation number to distinguish rotated logs
* <li> "%u" a unique number to resolve conflicts
* <li> "%%" translates to a single percent sign "%"
* </ul>
* If no "%g" field has been specified and the file count is greater
* than one, then the generation number will be added to the end of
* the generated filename, after a dot.
* <p>
* Thus for example a pattern of "%t/java%g.log" with a count of 2
* would typically cause log files to be written on Solaris to
* /var/tmp/java0.log and /var/tmp/java1.log whereas on Windows 95 they
* would be typically written to C:\TEMP\java0.log and C:\TEMP\java1.log
* <p>
* Generation numbers follow the sequence 0, 1, 2, etc.
* <p>
* Normally the "%u" unique field is set to 0. However, if the <tt>FileHandler
* tries to open the filename and finds the file is currently in use by
* another process it will increment the unique number field and try
* again. This will be repeated until <tt>FileHandler finds a file name that
* is not currently in use. If there is a conflict and no "%u" field has
* been specified, it will be added at the end of the filename after a dot.
* (This will be after any automatically added generation number.)
* <p>
* Thus if three processes were all trying to log to fred%u.%g.txt then
* they might end up using fred0.0.txt, fred1.0.txt, fred2.0.txt as
* the first file in their rotating sequences.
* <p>
* Note that the use of unique ids to avoid conflicts is only guaranteed
* to work reliably when using a local disk file system.
*
* @since 1.4
*/
public class FileHandler extends StreamHandler {
private MeteredStream meter;
private boolean append;
private int limit; // zero => no limit.
private int count;
private String pattern;
private String lockFileName;
private FileChannel lockFileChannel;
private File files[];
private static final int MAX_LOCKS = 100;
private static final java.util.HashMap<String, String> locks = new java.util.HashMap<>();
/**
* A metered stream is a subclass of OutputStream that
* (a) forwards all its output to a target stream
* (b) keeps track of how many bytes have been written
*/
private class MeteredStream extends OutputStream {
final OutputStream out;
int written;
MeteredStream(OutputStream out, int written) {
this.out = out;
this.written = written;
}
@Override
public void write(int b) throws IOException {
out.write(b);
written++;
}
@Override
public void write(byte buff[]) throws IOException {
out.write(buff);
written += buff.length;
}
@Override
public void write(byte buff[], int off, int len) throws IOException {
out.write(buff,off,len);
written += len;
}
@Override
public void flush() throws IOException {
out.flush();
}
@Override
public void close() throws IOException {
out.close();
}
}
private void open(File fname, boolean append) throws IOException {
int len = 0;
if (append) {
len = (int)fname.length();
}
FileOutputStream fout = new FileOutputStream(fname.toString(), append);
BufferedOutputStream bout = new BufferedOutputStream(fout);
meter = new MeteredStream(bout, len);
setOutputStream(meter);
}
/**
* Configure a FileHandler from LogManager properties and/or default values
* as specified in the class javadoc.
*/
private void configure() {
LogManager manager = LogManager.getLogManager();
String cname = getClass().getName();
pattern = manager.getStringProperty(cname + ".pattern", "%h/java%u.log");
limit = manager.getIntProperty(cname + ".limit", 0);
if (limit < 0) {
limit = 0;
}
count = manager.getIntProperty(cname + ".count", 1);
if (count <= 0) {
count = 1;
}
append = manager.getBooleanProperty(cname + ".append", false);
setLevel(manager.getLevelProperty(cname + ".level", Level.ALL));
setFilter(manager.getFilterProperty(cname + ".filter", null));
setFormatter(manager.getFormatterProperty(cname + ".formatter", new XMLFormatter()));
try {
setEncoding(manager.getStringProperty(cname +".encoding", null));
} catch (Exception ex) {
try {
setEncoding(null);
} catch (Exception ex2) {
// doing a setEncoding with null should always work.
// assert false;
}
}
}
/**
* Construct a default <tt>FileHandler. This will be configured
* entirely from <tt>LogManager properties (or their default values).
* <p>
* @exception IOException if there are IO problems opening the files.
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control")).
* @exception NullPointerException if pattern property is an empty String.
*/
public FileHandler() throws IOException, SecurityException {
checkPermission();
configure();
openFiles();
}
/**
* Initialize a <tt>FileHandler to write to the given filename.
* <p>
* The <tt>FileHandler is configured based on LogManager
* properties (or their default values) except that the given pattern
* argument is used as the filename pattern, the file limit is
* set to no limit, and the file count is set to one.
* <p>
* There is no limit on the amount of data that may be written,
* so use this with care.
*
* @param pattern the name of the output file
* @exception IOException if there are IO problems opening the files.
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control").
* @exception IllegalArgumentException if pattern is an empty string
*/
public FileHandler(String pattern) throws IOException, SecurityException {
if (pattern.length() < 1 ) {
throw new IllegalArgumentException();
}
checkPermission();
configure();
this.pattern = pattern;
this.limit = 0;
this.count = 1;
openFiles();
}
/**
* Initialize a <tt>FileHandler to write to the given filename,
* with optional append.
* <p>
* The <tt>FileHandler is configured based on LogManager
* properties (or their default values) except that the given pattern
* argument is used as the filename pattern, the file limit is
* set to no limit, the file count is set to one, and the append
* mode is set to the given <tt>append argument.
* <p>
* There is no limit on the amount of data that may be written,
* so use this with care.
*
* @param pattern the name of the output file
* @param append specifies append mode
* @exception IOException if there are IO problems opening the files.
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control").
* @exception IllegalArgumentException if pattern is an empty string
*/
public FileHandler(String pattern, boolean append) throws IOException,
SecurityException {
if (pattern.length() < 1 ) {
throw new IllegalArgumentException();
}
checkPermission();
configure();
this.pattern = pattern;
this.limit = 0;
this.count = 1;
this.append = append;
openFiles();
}
/**
* Initialize a <tt>FileHandler to write to a set of files. When
* (approximately) the given limit has been written to one file,
* another file will be opened. The output will cycle through a set
* of count files.
* <p>
* The <tt>FileHandler is configured based on LogManager
* properties (or their default values) except that the given pattern
* argument is used as the filename pattern, the file limit is
* set to the limit argument, and the file count is set to the
* given count argument.
* <p>
* The count must be at least 1.
*
* @param pattern the pattern for naming the output file
* @param limit the maximum number of bytes to write to any one file
* @param count the number of files to use
* @exception IOException if there are IO problems opening the files.
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control").
* @exception IllegalArgumentException if {@code limit < 0}, or {@code count < 1}.
* @exception IllegalArgumentException if pattern is an empty string
*/
public FileHandler(String pattern, int limit, int count)
throws IOException, SecurityException {
if (limit < 0 || count < 1 || pattern.length() < 1) {
throw new IllegalArgumentException();
}
checkPermission();
configure();
this.pattern = pattern;
this.limit = limit;
this.count = count;
openFiles();
}
/**
* Initialize a <tt>FileHandler to write to a set of files
* with optional append. When (approximately) the given limit has
* been written to one file, another file will be opened. The
* output will cycle through a set of count files.
* <p>
* The <tt>FileHandler is configured based on LogManager
* properties (or their default values) except that the given pattern
* argument is used as the filename pattern, the file limit is
* set to the limit argument, and the file count is set to the
* given count argument, and the append mode is set to the given
* <tt>append argument.
* <p>
* The count must be at least 1.
*
* @param pattern the pattern for naming the output file
* @param limit the maximum number of bytes to write to any one file
* @param count the number of files to use
* @param append specifies append mode
* @exception IOException if there are IO problems opening the files.
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control").
* @exception IllegalArgumentException if {@code limit < 0}, or {@code count < 1}.
* @exception IllegalArgumentException if pattern is an empty string
*
*/
public FileHandler(String pattern, int limit, int count, boolean append)
throws IOException, SecurityException {
if (limit < 0 || count < 1 || pattern.length() < 1) {
throw new IllegalArgumentException();
}
checkPermission();
configure();
this.pattern = pattern;
this.limit = limit;
this.count = count;
this.append = append;
openFiles();
}
/**
* Open the set of output files, based on the configured
* instance variables.
*/
private void openFiles() throws IOException {
LogManager manager = LogManager.getLogManager();
manager.checkPermission();
if (count < 1) {
throw new IllegalArgumentException("file count = " + count);
}
if (limit < 0) {
limit = 0;
}
// We register our own ErrorManager during initialization
// so we can record exceptions.
InitializationErrorManager em = new InitializationErrorManager();
setErrorManager(em);
// Create a lock file. This grants us exclusive access
// to our set of output files, as long as we are alive.
int unique = -1;
for (;;) {
unique++;
if (unique > MAX_LOCKS) {
throw new IOException("Couldn't get lock for " + pattern);
}
// Generate a lock file name from the "unique" int.
lockFileName = generate(pattern, 0, unique).toString() + ".lck";
// Now try to lock that filename.
// Because some systems (e.g., Solaris) can only do file locks
// between processes (and not within a process), we first check
// if we ourself already have the file locked.
synchronized(locks) {
if (locks.get(lockFileName) != null) {
// We already own this lock, for a different FileHandler
// object. Try again.
continue;
}
try {
lockFileChannel = FileChannel.open(Paths.get(lockFileName),
CREATE_NEW, WRITE);
} catch (FileAlreadyExistsException ix) {
// try the next lock file name in the sequence
continue;
}
boolean available;
try {
available = lockFileChannel.tryLock() != null;
// We got the lock OK.
} catch (IOException ix) {
// We got an IOException while trying to get the lock.
// This normally indicates that locking is not supported
// on the target directory. We have to proceed without
// getting a lock. Drop through.
available = true;
}
if (available) {
// We got the lock. Remember it.
locks.put(lockFileName, lockFileName);
break;
}
// We failed to get the lock. Try next file.
lockFileChannel.close();
}
}
files = new File[count];
for (int i = 0; i < count; i++) {
files[i] = generate(pattern, i, unique);
}
// Create the initial log file.
if (append) {
open(files[0], true);
} else {
rotate();
}
// Did we detect any exceptions during initialization?
Exception ex = em.lastException;
if (ex != null) {
if (ex instanceof IOException) {
throw (IOException) ex;
} else if (ex instanceof SecurityException) {
throw (SecurityException) ex;
} else {
throw new IOException("Exception: " + ex);
}
}
// Install the normal default ErrorManager.
setErrorManager(new ErrorManager());
}
/**
* Generate a file based on a user-supplied pattern, generation number,
* and an integer uniqueness suffix
* @param pattern the pattern for naming the output file
* @param generation the generation number to distinguish rotated logs
* @param unique a unique number to resolve conflicts
* @return the generated File
* @throws IOException
*/
private File generate(String pattern, int generation, int unique)
throws IOException {
File file = null;
String word = "";
int ix = 0;
boolean sawg = false;
boolean sawu = false;
while (ix < pattern.length()) {
char ch = pattern.charAt(ix);
ix++;
char ch2 = 0;
if (ix < pattern.length()) {
ch2 = Character.toLowerCase(pattern.charAt(ix));
}
if (ch == '/') {
if (file == null) {
file = new File(word);
} else {
file = new File(file, word);
}
word = "";
continue;
} else if (ch == '%') {
if (ch2 == 't') {
String tmpDir = System.getProperty("java.io.tmpdir");
if (tmpDir == null) {
tmpDir = System.getProperty("user.home");
}
file = new File(tmpDir);
ix++;
word = "";
continue;
} else if (ch2 == 'h') {
file = new File(System.getProperty("user.home"));
if (isSetUID()) {
// Ok, we are in a set UID program. For safety's sake
// we disallow attempts to open files relative to %h.
throw new IOException("can't use %h in set UID program");
}
ix++;
word = "";
continue;
} else if (ch2 == 'g') {
word = word + generation;
sawg = true;
ix++;
continue;
} else if (ch2 == 'u') {
word = word + unique;
sawu = true;
ix++;
continue;
} else if (ch2 == '%') {
word = word + "%";
ix++;
continue;
}
}
word = word + ch;
}
if (count > 1 && !sawg) {
word = word + "." + generation;
}
if (unique > 0 && !sawu) {
word = word + "." + unique;
}
if (word.length() > 0) {
if (file == null) {
file = new File(word);
} else {
file = new File(file, word);
}
}
return file;
}
/**
* Rotate the set of output files
*/
private synchronized void rotate() {
Level oldLevel = getLevel();
setLevel(Level.OFF);
super.close();
for (int i = count-2; i >= 0; i--) {
File f1 = files[i];
File f2 = files[i+1];
if (f1.exists()) {
if (f2.exists()) {
f2.delete();
}
f1.renameTo(f2);
}
}
try {
open(files[0], false);
} catch (IOException ix) {
// We don't want to throw an exception here, but we
// report the exception to any registered ErrorManager.
reportError(null, ix, ErrorManager.OPEN_FAILURE);
}
setLevel(oldLevel);
}
/**
* Format and publish a <tt>LogRecord.
*
* @param record description of the log event. A null record is
* silently ignored and is not published
*/
@Override
public synchronized void publish(LogRecord record) {
if (!isLoggable(record)) {
return;
}
super.publish(record);
flush();
if (limit > 0 && meter.written >= limit) {
// We performed access checks in the "init" method to make sure
// we are only initialized from trusted code. So we assume
// it is OK to write the target files, even if we are
// currently being called from untrusted code.
// So it is safe to raise privilege here.
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
rotate();
return null;
}
});
}
}
/**
* Close all the files.
*
* @exception SecurityException if a security manager exists and if
* the caller does not have <tt>LoggingPermission("control").
*/
@Override
public synchronized void close() throws SecurityException {
super.close();
// Unlock any lock file.
if (lockFileName == null) {
return;
}
try {
// Close the lock file channel (which also will free any locks)
lockFileChannel.close();
} catch (Exception ex) {
// Problems closing the stream. Punt.
}
synchronized(locks) {
locks.remove(lockFileName);
}
new File(lockFileName).delete();
lockFileName = null;
lockFileChannel = null;
}
private static class InitializationErrorManager extends ErrorManager {
Exception lastException;
@Override
public void error(String msg, Exception ex, int code) {
lastException = ex;
}
}
/**
* check if we are in a set UID program.
*/
private static native boolean isSetUID();
}
Other Java examples (source code examples)Here is a short list of links related to this Java FileHandler.java source code file: |
The search page
Other Java source code examples at this package level
Click here to learn more about this project
