原文
- 人在学校刷题，这道题实在想不出来，求助各路 V 友，第一个粘代码的 V 友，孩子请喝一杯星巴克
- 图下载地址：
https://wormhole.app/D6WqK#hJlIOWQXD_jGhs3Zr5KEPw
尝试编写了一个，包含文件随机切割以及合并
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.SeekableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;
import java.util.zip.ZipEntry;
import java.util.zip.ZipException;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;
public class Main {
public static final String chunkFilePrefix = "p";
public static final String logFileName = "splitlog.txt";
public static final int EOF = -1;
public static final int defaultBufferSize = 1024 << 2;
public static void main(String[] args) throws IOException {
// 切割文件，返回zip
Path zipFile = split(Paths.get("C:\\Users\\KevinBlandy\\Desktop\\test\\springboot.png"), 10);
// 解压zip，以及合并文件块儿
merge(zipFile, zipFile.resolveSibling("springboot-merge.png"));
}
/**
* 随机切割文件
* @param file 文件
* @param chunk 分块数量
* @return 包含了文件块以及切割日志的zip文件
* @throws IOException
*/
public static Path split (Path file, int chunk) throws IOException {
if(Files.notExists(file)){
throw new IllegalArgumentException(file.toString() + " 不存在");
}
// 文件大小
long fileSize = Files.size(file);
// 空文件
if (fileSize == 0) {
return null;
}
// 每个分块文件的最大大小 = (总大小 / 总个数)* 2
long chunkMaxSize = (fileSize / chunk) * 2;
// 切割的日志
Path logFile = file.resolveSibling(logFileName);
// 初始化分块文件
Path[] chunks = new Path[chunk];
for (int i = 0; i < chunk; i ++) {
Path chunkFile = file.resolveSibling(chunkFilePrefix + (i + 1));
if (Files.notExists(chunkFile)){
Files.createFile(chunkFile);
}
chunks[i] = chunkFile;
}
// 随机源
Random random = ThreadLocalRandom.current();
long position = 0;
// 随机切割
try(FileChannel fileChannel = FileChannel.open(file);
BufferedWriter logFileWriter = Files.newBufferedWriter(logFile, StandardOpenOption.CREATE)){
while (true) {
// 随机选一个分片文件，写入随机字节数据
int ramdonChunk = random.nextInt(chunk);
try(FileChannel chunkFileChannel = FileChannel.open(chunks[ramdonChunk], StandardOpenOption.CREATE, StandardOpenOption.APPEND)){
long write = fileChannel.transferTo(position, random.nextLong(1, chunkMaxSize + 1), chunkFileChannel);
if (write == 0) {
break;
}
position += write;
// 写入日志
logFileWriter.write(String.format("%d\t%d", ramdonChunk + 1, write));
logFileWriter.newLine();
logFileWriter.flush();
}
}
}
// 写入到zip文件
Path zip = file.resolveSibling("files.zip");
try(ZipOutputStream zipOutputStream = new ZipOutputStream(Files.newOutputStream(zip, StandardOpenOption.CREATE))){
// 写入分块文件
for (Path chunkFile : chunks) {
zipOutputStream.putNextEntry(new ZipEntry(chunkFile.getFileName().toString()));
Files.copy(chunkFile, zipOutputStream);
}
// 写入日志文件
zipOutputStream.putNextEntry(new ZipEntry(logFile.getFileName().toString()));
Files.copy(logFile, zipOutputStream);
}
// 删除分块文件
for (Path chunkFile : chunks) {
Files.delete(chunkFile);
}
// 删除日志文件
Files.delete(logFile);
return zip;
}
/**
* 合并文件
* @param zipFile 压缩文件
* @param targetFile 合并后的目标文件
* @throws IOException
* @throws ZipException
*/
public static void merge (Path zip, Path targetFile) throws ZipException, IOException {
// 文件所在目录
Path dir = zip.getParent();
// 解压所有文件到目录
try (ZipFile zipFile = new ZipFile(zip.toFile())) {
try (ZipInputStream zipInputStream = new ZipInputStream(Files.newInputStream(zip))) {
ZipEntry zipEntry = null;
while ((zipEntry = zipInputStream.getNextEntry()) != null) {
String entryName = zipEntry.getName();
Path entryFile = dir.resolve(entryName);
if (zipEntry.isDirectory() && !Files.isDirectory(entryFile)) {
Files.createDirectories(entryFile);
} else {
try (InputStream zipEntryInputStream = zipFile.getInputStream(zipEntry)) {
Files.copy(zipEntryInputStream, entryFile);
}
}
}
}
}
// 文件块流
Map<String, FileChannel> chunkFiles = new HashMap<>();
// 创建目标文件，也是还原后的图片文件
try(SeekableByteChannel targetFileChannel = Files.newByteChannel(targetFile, StandardOpenOption.CREATE, StandardOpenOption.WRITE);
// 读取日志文件
BufferedReader logReader = Files.newBufferedReader(dir.resolve(logFileName))){
String line = null;
while ((line = logReader.readLine()) != null) {
// 读取每一行
String[] item = line.split("\t");
// 块文件
String fileNumber = item[0];
// 长度
long size = Long.parseLong(item[1]);
// 文件流
FileChannel chunkFileChannel = chunkFiles.computeIfAbsent(fileNumber, key -> {
try {
return FileChannel.open(dir.resolve(chunkFilePrefix + fileNumber));
} catch (IOException e) {
throw new RuntimeException(e);
}
});
// 复制到目标文件
copyN(chunkFileChannel, targetFileChannel, size);
}
}
// 关闭所有流
chunkFiles.values().stream().forEach(t -> {
try {
t.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
});
}
// 从src 复制n个字节到dest
public static int copyN (ReadableByteChannel src, WritableByteChannel dest, long n) throws IOException {
if (n < 0) {
throw new IllegalArgumentException();
}
ByteBuffer buffer = ByteBuffer.allocate((int) Math.min(n, defaultBufferSize));
int readCount = 0;
while (readCount < n) {
if ((n - readCount) < buffer.capacity()) {
buffer.limit((int) (n - readCount));
}
int count = src.read(buffer);
if (count == EOF) {
break;
}
readCount += count;
buffer.flip();
while (buffer.hasRemaining()) {
dest.write(buffer);
}
buffer.clear();
}
return readCount;
}
}
本地试了一下，可以正常的随机切割文件以及合并。暂时没发现啥问题还。