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Comprehensive Java common library (Java7+)
/*
* Copyright (C) 2015-2017 S.Violet
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Project GitHub: https://github.com/shepherdviolet/thistle
* Email: [email protected]
*/
package sviolet.thistle.util.file;
import sviolet.thistle.util.common.PlatformUtils;
import java.io.*;
import java.lang.reflect.Method;
import java.nio.MappedByteBuffer;
import java.security.AccessController;
import java.security.PrivilegedAction;
/**
* 文件工具
*
* @author S.Violet
*/
public class FileUtils {
private static final String SUN_MISC_CLEANER = "sun.misc.Cleaner";
/**
* 向文件写入字符串
* @param file 文件
* @param msg 字符串
* @param append true:追加 false:覆盖
*/
public static void writeString(File file, String msg, boolean append) throws IOException {
writeString(file, msg, "utf-8", append);
}
/**
* 向文件写入字符串
* @param file 文件
* @param msg 字符串
* @param charset 字符编码
* @param append true:追加 false:覆盖
*/
public static void writeString(File file, String msg, String charset, boolean append) throws IOException {
File dirFile = file.getParentFile();
if (dirFile != null && !dirFile.exists()){
if (!dirFile.mkdirs()){
throw new IOException("Can not make directory before write string to file, path:" + dirFile.getAbsolutePath());
}
}
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file, append), charset));
writer.write(msg);
} finally {
try { if (writer != null) {writer.flush();} } catch (IOException ignored) { }
try { if (writer != null) {writer.close();} } catch (IOException ignored) { }
}
}
/**
* 读取整个文件(字符串形式), 仅限于读取小文件, 小心OOM
* @param file 文件
* @param maxLength 最大长度, 如果文件大小超过该设定值, 会抛出异常
* @return 字符串
*/
public static String readString(File file, int maxLength) throws LengthOutOfLimitException, IOException {
return readString(file, "utf-8", maxLength);
}
/**
* 读取整个文件(字符串形式), 仅限于读取小文件, 小心OOM
* @param file 文件
* @param charset 字符编码
* @param maxLength 最大长度, 如果文件大小超过该设定值, 会抛出异常
* @return 字符串
*/
public static String readString(File file, String charset, int maxLength) throws LengthOutOfLimitException, IOException {
if (!file.exists() || !file.isFile()) {
throw new FileNotFoundException("File not found, path:" + file.getAbsolutePath());
}
if (file.length() > maxLength){
throw new LengthOutOfLimitException("File length out of limit, file:" + file.getAbsolutePath() + ", length:" + file.length());
}
BufferedReader bufferedReader = null;
try {
bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(file), charset));
StringBuilder stringBuilder = new StringBuilder();
char[] buff = new char[1024];
int length;
while ((length = bufferedReader.read(buff)) >= 0) {
stringBuilder.append(buff, 0, length);
}
return stringBuilder.toString();
} finally {
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (Exception ignore){
}
}
}
}
/**
* 读取文件的头部数据
* @param file 文件
* @param start 起始位置
* @param buffer 获取的数据
* @throws IOException exception
*/
public static long readHead(File file, int start, byte[] buffer) throws IOException {
if (file == null || !file.exists()){
return 0;
}
RandomAccessFile randomAccessFile = null;
try{
randomAccessFile = new RandomAccessFile(file, "r");
randomAccessFile.seek(start);
return randomAccessFile.read(buffer);
} finally {
if (randomAccessFile != null){
try {
randomAccessFile.close();
} catch (IOException ignored) {
}
}
}
}
/************************************************************************************************************
* MappedByteBuffer:注意事项
* MappedByteBuffer在一些运行时环境中(例如HOTSPOT), 会占用内存并占用文件句柄, 导致文件无法读写删除, 直到对象被GC.
* 且没有常规办法可以回收资源. ANDROID中不存在此问题.
* isMappedByteBufferCanClean方法可以判断当前运行环境是否能手动回收MappedByteBuffer, 无法手动回收的运行时环境建
* 议不要随便使用MappedByteBuffer, 改用传统的IO.
* cleanMappedByteBuffer方法可以手动回收MappedByteBuffer.
*
* MappedByteBuffer是通过下列方法获得的:
* FileInputStream inputStream = new FileInputStream(file);
* Channel channel = inputStream.getChannel();
* MappedByteBuffer byteBuffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
*/
private static volatile int isMappedByteBufferCanClean = -1;
private static Class directByteBufferClass;
private static Method directByteBufferCleanerMethod;
private static Method cleanerCleanMethod;
/**
* 判断当前运行环境是否能手动回收MappedByteBuffer, 无法手动回收的运行时建议不要随便使用MappedByteBuffer, 改用传统的IO.
* @return true:支持手动回收MappedByteBuffer
*/
public static boolean isMappedByteBufferCanClean(){
if (isMappedByteBufferCanClean >= 0){
return isMappedByteBufferCanClean == 0;
}
//安卓平台不可用手动回收, 但是不回收也不会存在文件被锁的问题
if (PlatformUtils.PLATFORM == PlatformUtils.Platform.DALVIK){
isMappedByteBufferCanClean = 1;
return false;
}
return AccessController.doPrivileged(new PrivilegedAction() {
@Override
public Boolean run() {
try {
directByteBufferClass = Class.forName("java.nio.DirectByteBuffer");
directByteBufferCleanerMethod = directByteBufferClass.getDeclaredMethod("cleaner");
if (directByteBufferCleanerMethod == null){
throw new Exception("Method cleaner can not find in java.nio.DirectByteBuffer");
}
if (!SUN_MISC_CLEANER.equals(directByteBufferCleanerMethod.getReturnType().getName())){
throw new Exception("Return type of method cleaner is not sun.misc.Cleaner");
}
directByteBufferCleanerMethod.setAccessible(true);
Class cleanerClass = Class.forName("sun.misc.Cleaner");
cleanerCleanMethod = cleanerClass.getDeclaredMethod("clean");
if (cleanerCleanMethod == null){
throw new Exception("Method clean can not find in sun.misc.Cleaner");
}
cleanerCleanMethod.setAccessible(true);
isMappedByteBufferCanClean = 0;
return true;
} catch (Throwable t) {
// new Exception("WARNING:This jre environment can not clean MappedByteBuffer manually(1), isMappedByteBufferCanClean = false", t).printStackTrace();
System.out.println("WARNING:This jre environment can not clean MappedByteBuffer manually(1), isMappedByteBufferCanClean = false");
isMappedByteBufferCanClean = 1;
return false;
}
}
});
}
/**
* 手动回收MappedByteBuffer.
* @return true:回收成功
*/
public static boolean cleanMappedByteBuffer(final MappedByteBuffer mappedByteBuffer) {
if (mappedByteBuffer == null){
return false;
}
if (isMappedByteBufferCanClean()){
return AccessController.doPrivileged(new PrivilegedAction() {
@Override
public Boolean run() {
try {
if (!directByteBufferClass.isAssignableFrom(mappedByteBuffer.getClass())){
return false;
}
cleanerCleanMethod.invoke(directByteBufferCleanerMethod.invoke(mappedByteBuffer));
return true;
} catch (Throwable t) {
// new Exception("WARNING:This jre environment can not clean MappedByteBuffer manually(2), isMappedByteBufferCanClean = false", t).printStackTrace();
System.out.println("WARNING:This jre environment can not clean MappedByteBuffer manually(2), isMappedByteBufferCanClean = false");
isMappedByteBufferCanClean = 1;
return false;
}
}
});
} else {
return false;
}
}
/****************************************************************************************************
* Exceptions
*/
public static class LengthOutOfLimitException extends Exception {
public LengthOutOfLimitException(String message) {
super(message);
}
}
}