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Hutool是一个小而全的Java工具类库，通过静态方法封装，降低相关API的学习成本，提高工作效率，使Java拥有函数式语言般的优雅，让Java语言也可以“甜甜的”。
package cn.hutool.core.io;
import cn.hutool.core.io.copy.ChannelCopier;
import cn.hutool.core.lang.Assert;
import cn.hutool.core.util.CharsetUtil;
import cn.hutool.core.util.StrUtil;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.MappedByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.charset.Charset;
/**
* NIO相关工具封装，主要针对Channel读写、拷贝等封装
*
* @author looly
* @since 5.5.3
*/
public class NioUtil {
/**
* 默认缓存大小 8192
*/
public static final int DEFAULT_BUFFER_SIZE = 2 << 12;
/**
* 默认中等缓存大小 16384
*/
public static final int DEFAULT_MIDDLE_BUFFER_SIZE = 2 << 13;
/**
* 默认大缓存大小 32768
*/
public static final int DEFAULT_LARGE_BUFFER_SIZE = 2 << 14;
/**
* 数据流末尾
*/
public static final int EOF = -1;
/**
* 拷贝流 thanks to: https://github.com/venusdrogon/feilong-io/blob/master/src/main/java/com/feilong/io/IOWriteUtil.java
* 本方法不会关闭流
*
* @param in 输入流
* @param out 输出流
* @param bufferSize 缓存大小
* @param streamProgress 进度条
* @return 传输的byte数
* @throws IORuntimeException IO异常
*/
public static long copyByNIO(InputStream in, OutputStream out, int bufferSize, StreamProgress streamProgress) throws IORuntimeException {
return copyByNIO(in, out, bufferSize, -1, streamProgress);
}
/**
* 拷贝流
* 本方法不会关闭流
*
* @param in 输入流
* @param out 输出流
* @param bufferSize 缓存大小
* @param count 最大长度
* @param streamProgress 进度条
* @return 传输的byte数
* @throws IORuntimeException IO异常
* @since 5.7.8
*/
public static long copyByNIO(InputStream in, OutputStream out, int bufferSize, long count, StreamProgress streamProgress) throws IORuntimeException {
final long copySize = copy(Channels.newChannel(in), Channels.newChannel(out), bufferSize, count, streamProgress);
IoUtil.flush(out);
return copySize;
}
/**
* 拷贝文件Channel，使用NIO，拷贝后不会关闭channel
*
* @param inChannel {@link FileChannel}
* @param outChannel {@link FileChannel}
* @return 拷贝的字节数
* @throws IORuntimeException IO异常
* @since 5.5.3
*/
public static long copy(FileChannel inChannel, FileChannel outChannel) throws IORuntimeException {
Assert.notNull(inChannel, "In channel is null!");
Assert.notNull(outChannel, "Out channel is null!");
try {
return copySafely(inChannel, outChannel);
} catch (IOException e) {
throw new IORuntimeException(e);
}
}
/**
* 文件拷贝实现
*
*
* FileChannel#transferTo 或 FileChannel#transferFrom 的实现是平台相关的，需要确保低版本平台的兼容性
* 例如 android 7以下平台在使用 ZipInputStream 解压文件的过程中，
* 通过 FileChannel#transferFrom 传输到文件时，其返回值可能小于 totalBytes，不处理将导致文件内容缺失
*
* // 错误写法，dstChannel.transferFrom 返回值小于 zipEntry.getSize()，导致解压后文件内容缺失
* try (InputStream srcStream = zipFile.getInputStream(zipEntry);
* ReadableByteChannel srcChannel = Channels.newChannel(srcStream);
* FileOutputStream fos = new FileOutputStream(saveFile);
* FileChannel dstChannel = fos.getChannel()) {
* dstChannel.transferFrom(srcChannel, 0, zipEntry.getSize());
* }
*
*
* @param inChannel 输入通道
* @param outChannel 输出通道
* @return 输入通道的字节数
* @throws IOException 发生IO错误
* @link http://androidxref.com/6.0.1_r10/xref/libcore/luni/src/main/java/java/nio/FileChannelImpl.java
* @link http://androidxref.com/7.0.0_r1/xref/libcore/ojluni/src/main/java/sun/nio/ch/FileChannelImpl.java
* @link http://androidxref.com/7.0.0_r1/xref/libcore/ojluni/src/main/native/FileChannelImpl.c
* @author z8g
* @since 5.7.21
*/
private static long copySafely(FileChannel inChannel, FileChannel outChannel) throws IOException {
final long totalBytes = inChannel.size();
for (long pos = 0, remaining = totalBytes; remaining > 0; ) { // 确保文件内容不会缺失
final long writeBytes = inChannel.transferTo(pos, remaining, outChannel); // 实际传输的字节数
pos += writeBytes;
remaining -= writeBytes;
}
return totalBytes;
}
/**
* 拷贝流，使用NIO，不会关闭channel
*
* @param in {@link ReadableByteChannel}
* @param out {@link WritableByteChannel}
* @return 拷贝的字节数
* @throws IORuntimeException IO异常
* @since 4.5.0
*/
public static long copy(ReadableByteChannel in, WritableByteChannel out) throws IORuntimeException {
return copy(in, out, DEFAULT_BUFFER_SIZE);
}
/**
* 拷贝流，使用NIO，不会关闭channel
*
* @param in {@link ReadableByteChannel}
* @param out {@link WritableByteChannel}
* @param bufferSize 缓冲大小，如果小于等于0，使用默认
* @return 拷贝的字节数
* @throws IORuntimeException IO异常
* @since 4.5.0
*/
public static long copy(ReadableByteChannel in, WritableByteChannel out, int bufferSize) throws IORuntimeException {
return copy(in, out, bufferSize, null);
}
/**
* 拷贝流，使用NIO，不会关闭channel
*
* @param in {@link ReadableByteChannel}
* @param out {@link WritableByteChannel}
* @param bufferSize 缓冲大小，如果小于等于0，使用默认
* @param streamProgress {@link StreamProgress}进度处理器
* @return 拷贝的字节数
* @throws IORuntimeException IO异常
*/
public static long copy(ReadableByteChannel in, WritableByteChannel out, int bufferSize, StreamProgress streamProgress) throws IORuntimeException {
return copy(in, out, bufferSize, -1, streamProgress);
}
/**
* 拷贝流，使用NIO，不会关闭channel
*
* @param in {@link ReadableByteChannel}
* @param out {@link WritableByteChannel}
* @param bufferSize 缓冲大小，如果小于等于0，使用默认
* @param count 读取总长度
* @param streamProgress {@link StreamProgress}进度处理器
* @return 拷贝的字节数
* @throws IORuntimeException IO异常
* @since 5.7.8
*/
public static long copy(ReadableByteChannel in, WritableByteChannel out, int bufferSize, long count, StreamProgress streamProgress) throws IORuntimeException {
return new ChannelCopier(bufferSize, count, streamProgress).copy(in, out);
}
/**
* 从流中读取内容，读取完毕后并不关闭流
*
* @param channel 可读通道，读取完毕后并不关闭通道
* @param charset 字符集
* @return 内容
* @throws IORuntimeException IO异常
* @since 4.5.0
*/
public static String read(ReadableByteChannel channel, Charset charset) throws IORuntimeException {
FastByteArrayOutputStream out = read(channel);
return null == charset ? out.toString() : out.toString(charset);
}
/**
* 从流中读取内容，读到输出流中
*
* @param channel 可读通道，读取完毕后并不关闭通道
* @return 输出流
* @throws IORuntimeException IO异常
*/
public static FastByteArrayOutputStream read(ReadableByteChannel channel) throws IORuntimeException {
final FastByteArrayOutputStream out = new FastByteArrayOutputStream();
copy(channel, Channels.newChannel(out));
return out;
}
/**
* 从FileChannel中读取UTF-8编码内容
*
* @param fileChannel 文件管道
* @return 内容
* @throws IORuntimeException IO异常
*/
public static String readUtf8(FileChannel fileChannel) throws IORuntimeException {
return read(fileChannel, CharsetUtil.CHARSET_UTF_8);
}
/**
* 从FileChannel中读取内容，读取完毕后并不关闭Channel
*
* @param fileChannel 文件管道
* @param charsetName 字符集
* @return 内容
* @throws IORuntimeException IO异常
*/
public static String read(FileChannel fileChannel, String charsetName) throws IORuntimeException {
return read(fileChannel, CharsetUtil.charset(charsetName));
}
/**
* 从FileChannel中读取内容
*
* @param fileChannel 文件管道
* @param charset 字符集
* @return 内容
* @throws IORuntimeException IO异常
*/
public static String read(FileChannel fileChannel, Charset charset) throws IORuntimeException {
MappedByteBuffer buffer;
try {
buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size()).load();
} catch (IOException e) {
throw new IORuntimeException(e);
}
return StrUtil.str(buffer, charset);
}
/**
* 关闭
* 关闭失败不会抛出异常
*
* @param closeable 被关闭的对象
*/
public static void close(AutoCloseable closeable) {
if (null != closeable) {
try {
closeable.close();
} catch (Exception e) {
// 静默关闭
}
}
}
}
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