com.mchange.util.impl.SyncedProperties Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java v.0.2.3
*
* Copyright (C) 2012 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1, as
* published by the Free Software Foundation.
*
* This software 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this software; see the file LICENSE. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*/
package com.mchange.util.impl;
import java.io.*;
import java.util.*;
import com.mchange.io.InputStreamUtils;
import com.mchange.io.OutputStreamUtils;
public class SyncedProperties
{
private final static String[] SA_TEMPLATE = new String[0];
private final static byte H_START_BYTE = (byte) '#';
private final static byte[] H_LF_BYTES;
private final static String ASCII = "8859_1";
static
{
try
{H_LF_BYTES = System.getProperty("line.separator", "\r\n").getBytes(ASCII);}
catch (UnsupportedEncodingException e)
{throw new InternalError("Encoding " + ASCII + " not supported ?!?");}
}
Properties props;
byte[] headerBytes;
File file;
long last_mod = -1;
public SyncedProperties(File file, String header) throws IOException
{this(file, makeHeaderBytes(header));}
public SyncedProperties(File file, String[] header) throws IOException
{this(file, makeHeaderBytes(header));}
public SyncedProperties(File file) throws IOException
{this(file, (byte[]) null);}
private SyncedProperties(File file, byte[] headerBytes) throws IOException
{
if (file.exists())
{
if (!file.isFile())
throw new IOException(file.getPath() + ": Properties file can't be a directory or special file!");
if (headerBytes == null)
{
//I'd rather not use a localized reader; I'd rather have a fixed, location
//independent file format, but Properties uses a localized print stream to write.
BufferedReader br = null;
try
{
br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
List list = new LinkedList();
String line = br.readLine();
while (line.trim().equals(""))
line = br.readLine();
while (line.charAt(0) == '#')
list.add(line.substring(1).trim());
headerBytes = makeHeaderBytes((String[]) list.toArray(SA_TEMPLATE));
}
finally
{if (br != null) br.close();}
}
}
/*
else //workaround fact that canWrite() returns false one non-existent but creatable files by creating...
{
OutputStream os = null;
try
{
os = new FileOutputStream(file);
os.write('\n');
os.flush();
}
finally
{if (os == null) os.close();}
}
*/
if (!file.canWrite())
throw new IOException("Can't write to file " + file.getPath());
this.props = new Properties();
this.headerBytes = headerBytes;
this.file = file;
ensureUpToDate();
}
public synchronized String getProperty(String property) throws IOException
{
ensureUpToDate();
return props.getProperty(property);
}
public synchronized String getProperty(String property, String defaultValue) throws IOException
{
String out = props.getProperty(property);
return (out == null ? defaultValue : out);
}
public synchronized void put(String property, String value) throws IOException
{
ensureUpToDate();
props.put(property, value);
rewritePropsFile();
}
public synchronized void remove(String property) throws IOException
{
ensureUpToDate();
props.remove(property);
rewritePropsFile();
}
public synchronized void clear() throws IOException
{
ensureUpToDate();
props.clear();
rewritePropsFile();
}
public synchronized boolean contains(String value) throws IOException
{
ensureUpToDate();
return props.contains(value);
}
public synchronized boolean containsKey(String key) throws IOException
{
ensureUpToDate();
return props.containsKey(key);
}
public synchronized Enumeration elements() throws IOException
{
ensureUpToDate();
return props.elements();
}
public synchronized Enumeration keys() throws IOException
{
ensureUpToDate();
return props.keys();
}
public synchronized int size() throws IOException
{
ensureUpToDate();
return props.size();
}
public synchronized boolean isEmpty() throws IOException
{
ensureUpToDate();
return props.isEmpty();
}
private synchronized void ensureUpToDate() throws IOException
{
long new_mod = file.lastModified();
if (new_mod > last_mod)
{
InputStream is = null;
try
{
is = new BufferedInputStream(new FileInputStream(file));
props.clear();
props.load(is);
this.last_mod = new_mod;
}
finally
{InputStreamUtils.attemptClose(is);}
}
}
private synchronized void rewritePropsFile() throws IOException
{
OutputStream os = null;
try
{
os = new BufferedOutputStream(new FileOutputStream(file));
if (headerBytes != null) os.write(headerBytes);
props.store(os, null);
os.flush();
this.last_mod = file.lastModified();
}
finally
{OutputStreamUtils.attemptClose(os);}
}
private static byte[] makeHeaderBytes(String[] header)
{
try
{
ByteArrayOutputStream baos = new ByteArrayOutputStream();
for (int i = 0, len = header.length; i < len; ++i)
{
baos.write(H_START_BYTE);
baos.write(header[i].getBytes());
baos.write(H_LF_BYTES);
}
return baos.toByteArray();
}
catch (IOException e)
{throw new InternalError("IOException working with ByteArrayOutputStream?!?");}
}
private static byte[] makeHeaderBytes(String header)
{
try
{
ByteArrayOutputStream baos = new ByteArrayOutputStream();
baos.write(H_START_BYTE);
baos.write(header.getBytes());
baos.write(H_LF_BYTES);
return baos.toByteArray();
}
catch (IOException e)
{throw new InternalError("IOException working with ByteArrayOutputStream?!?");}
}
}