简介

这几天在做通过流下载zip文件以及上传zip文件不解压读取zip文件内容的功能，在读取zip文件内容的时候遇到了size为-1的情况，在此记录下遇到的情况、解决办法、以及未解决的问题。

示例

将上传和下载zip文件的功能做成了一个示例，放到了github上，链接：export-import-zip-use-stream，可以尝试运行下。

遇到的问题

通过流下载zip文件之后，再次导入该zip文件，不解压读取zip文件内容，发现ZipEntry的size()返回-1，如下图所示：

但是尝试使用系统自带的压缩软件压缩了一个zip文件，并上传读取，发现一切正常，size不为-1。使用zipinfo命令查看两个文件作为对比，如下：

可以看到上面文件是通过导出功能生成的，红框里缺少size。而下面的是系统压缩软件压缩的zip文件，红框里面带有size大小。故猜测可能是由于代码里生成ZipEntry的时候没有设置size，compressize，crc32等属性的原因。

读取zip文件时ZipEntry的size为-1解决办法

直接读取当前ZipEntry的流，直到为-1为止，代码如下：

@PostMapping("import")
@ResponseBody
public void importZip(@RequestParam("file")MultipartFile file) throws IOException {ZipInputStream zipInputStream = new ZipInputStream(file.getInputStream());ZipEntry zipEntry;while ((zipEntry = zipInputStream.getNextEntry()) != null) {if (zipEntry.isDirectory()) {// do nothing}else {String name = zipEntry.getName();long size = zipEntry.getSize();// unknown size// ZipEntry的size可能为-1，表示未知// 通过上面的几种方式下载，就会产生这种情况if (size == -1) {ByteArrayOutputStream baos = new ByteArrayOutputStream();while (true) {int bytes = zipInputStream.read();if (bytes == -1) break;baos.write(bytes);}baos.close();System.out.println(String.format("Name:%s,Content:%s",name,new String(baos.toByteArray())));} else { // ZipEntry的size正常byte[] bytes = new byte[(int) zipEntry.getSize()];zipInputStream.read(bytes, 0, (int) zipEntry.getSize());System.out.println(String.format("Name:%s,Content:%s",name,new String(bytes)));}}}zipInputStream.closeEntry();zipInputStream.close();
}

此时可以正确读取文件内容。

下载文件时设置size的解决办法

需要设置ZipEntry的size，compresSize以及crc32等属性。

例如：

public static void main(String[] args) throws IOException {File infile  = new File("test_file.pdf");File outfile = new File("test.zip");try (FileInputStream  fis = new FileInputStream(infile);FileOutputStream fos = new FileOutputStream(outfile);ZipOutputStream  zos = new ZipOutputStream(fos) ) {byte[]  buffer = new byte[1024];ZipEntry entry = new ZipEntry("data");precalc(entry, fis.getChannel());zos.putNextEntry(entry);for(int bytesRead; (bytesRead = fis.read(buffer)) >= 0; )zos.write(buffer, 0, bytesRead);zos.closeEntry();}try(FileInputStream fin = new FileInputStream(outfile);ZipInputStream  zis = new ZipInputStream(fin) ) {ZipEntry entry = zis.getNextEntry();System.out.println("Entry size: " + entry.getSize());System.out.println("Compressed size: " + entry.getCompressedSize());System.out.println("CRC: " + entry.getCrc());zis.closeEntry();}
}private static void precalc(ZipEntry entry, FileChannel fch) throws IOException {long uncompressed = fch.size();int method = entry.getMethod();CRC32 crc = new CRC32();Deflater def;byte[] drain;if(method != ZipEntry.STORED) {def   = new Deflater(Deflater.DEFAULT_COMPRESSION, true);drain = new byte[1024];}else {def   = null;drain = null;}ByteBuffer buf = ByteBuffer.allocate((int)Math.min(uncompressed, 4096));for(int bytesRead; (bytesRead = fch.read(buf)) != -1; buf.clear()) {crc.update(buf.array(), buf.arrayOffset(), bytesRead);if(def!=null) {def.setInput(buf.array(), buf.arrayOffset(), bytesRead);while(!def.needsInput()) def.deflate(drain, 0, drain.length);}}entry.setSize(uncompressed);if(def!=null) {def.finish();while(!def.finished()) def.deflate(drain, 0, drain.length);entry.setCompressedSize(def.getBytesWritten());}entry.setCrc(crc.getValue());fch.position(0);
}

另外一种解决方法，通过Enumeration 

一、分析下原因

（PS:参考大佬的博客地址：https://blog.csdn.net/zbj18314469395/article/details/84109499）

二、解决办法：

把判断条件由【(ze=zin.getNextEntry())!=null】换成【zipEnum.hasMoreElements ()】
使用了枚举， Enumeration 接口（枚举）。

通常用 Enumeration 中的以下两个方法打印向量中的所有元素：

(1) boolean hasMoreElements(); // 是否还有元素，如果返回 true ，则表示至少含有一个元素

(2) public Object nextElement(); // 如果 Enumeration 枚举对象还含有元素，该方法返回对象中的下一个元素。如果没有，则抛出NoSuchElementException 异常。

附上我的代码，已经修改过的，大家可以参考一下

public void processFile(String path) throws Exception {ZipFile zf = new ZipFile(path);//主要是这块java.util.Enumeration zipEnum = zf.entries();InputStream in = new BufferedInputStream(new FileInputStream(path));ZipInputStream zin = new ZipInputStream(in, Charset.forName("gbk"));ZipEntry ze;//重点是是这块的判断while (zipEnum.hasMoreElements()) {ze = (ZipEntry) zipEnum.nextElement();if (!ze.getName().contains("__MACOSX") && !ze.getName().contains(".DS_Store")) {if (!ze.isDirectory()) {System.out.println("##name##" + ze.getName());System.out.println("##size##" + ze.getSize());}}}zin.closeEntry();}

另外一个例子：

https://github.com/yrom/shrinker/blob/master/shrinker/src/main/java/net/yrom/tools/JarProcessor.java

package net.yrom.tools;import com.google.common.collect.ImmutableList;import org.apache.commons.io.IOUtils;import org.apache.commons.io.output.ByteArrayOutputStream;import java.io.ByteArrayInputStream;import java.io.EOFException;import java.io.IOException;import java.io.OutputStream;import java.io.UncheckedIOException;import java.nio.file.Files;import java.nio.file.Path;import java.util.List;import java.util.function.Function;import java.util.stream.Collectors;import java.util.zip.CRC32;import java.util.zip.ZipEntry;import java.util.zip.ZipInputStream;import java.util.zip.ZipOutputStream;
/*** @author yrom* @version 2017/11/29*/
class JarProcessor extends ClassesProcessor {JarProcessor(Function<byte[], byte[]> classTransform, Path src, Path dst) {super(classTransform, src, dst);}@Overridepublic void proceed() {try {List<Pair<String, byte[]>> entryList = readZipEntries(src).parallelStream().map(this::transformClassBlob).collect(Collectors.toList());if (entryList.isEmpty()) return;try (OutputStream fileOut = Files.newOutputStream(dst)) {ByteArrayOutputStream buffer = zipEntries(entryList);buffer.writeTo(fileOut);}} catch (IOException e) {throw new RuntimeException("Reading jar entries failure", e);}}private ByteArrayOutputStream zipEntries(List<Pair<String, byte[]>> entryList) throws IOException {ByteArrayOutputStream buffer = new ByteArrayOutputStream(8192);try (ZipOutputStream jar = new ZipOutputStream(buffer)) {jar.setMethod(ZipOutputStream.STORED);final CRC32 crc = new CRC32();for (Pair<String, byte[]> entry : entryList) {byte[] bytes = entry.second;final ZipEntry newEntry = new ZipEntry(entry.first);newEntry.setMethod(ZipEntry.STORED); // chose STORED methodcrc.reset();crc.update(entry.second);newEntry.setCrc(crc.getValue());newEntry.setSize(bytes.length);writeEntryToJar(newEntry, bytes, jar);}jar.flush();}return buffer;}private Pair<String, byte[]> transformClassBlob(Pair<String, byte[]> entry) {byte[] bytes = entry.second;entry.second = classTransform.apply(bytes);return entry;}private List<Pair<String, byte[]>> readZipEntries(Path src) throws IOException {ImmutableList.Builder<Pair<String, byte[]>> list = ImmutableList.builder();try (ZipInputStream zip = new ZipInputStream(new ByteArrayInputStream(Files.readAllBytes(src)))) {for (ZipEntry entry = zip.getNextEntry();entry != null;entry = zip.getNextEntry()) {String name = entry.getName();if (!name.endsWith(".class")) {
// skipcontinue;}long entrySize = entry.getSize();if (entrySize >= Integer.MAX_VALUE) {throw new OutOfMemoryError("Too large class file " + name + ", size is " + entrySize);}byte[] bytes = readByteArray(zip, (int) entrySize);list.add(Pair.of(name, bytes));}}return list.build();}private byte[] readByteArray(ZipInputStream zip, int expected) throws IOException {if (expected == -1) { // unknown sizereturn IOUtils.toByteArray(zip);}final byte[] bytes = new byte[expected];int read = 0;do {int n = zip.read(bytes, read, expected - read);if (n <= 0) {break;}read += n;} while (read < expected);if (expected != bytes.length) {throw new EOFException("unexpected EOF");}return bytes;}private static void writeEntryToJar(ZipEntry entry, byte[] bytes, ZipOutputStream jar) {try {jar.putNextEntry(entry);jar.write(bytes);jar.closeEntry();} catch (IOException e) {throw new UncheckedIOException(e);}}// mutable pairstatic class Pair<F, S> {F first;S second;Pair(F first, S second) {this.first = first;this.second = second;}static <F, S> Pair<F, S> of(F first, S second) {return new Pair<>(first, second);}}
}

zip例子：

https://www.programcreek.com/java-api-examples/?code=FutureSonic/FutureSonic-Server/FutureSonic-Server-master/futuresonic-main/src/main/java/net/sourceforge/subsonic/controller/DownloadController.java

/*** Computes the CRC checksum for the given file.** @param file The file to compute checksum for.* @return A CRC32 checksum.* @throws IOException If an I/O error occurs.*/private static long computeCrc(File file) throws IOException {CRC32 crc = new CRC32();InputStream in = new FileInputStream(file);try {byte[] buf = new byte[8192];int n = in.read(buf);while (n != -1) {crc.update(buf, 0, n);n = in.read(buf);}} finally {in.close();}return crc.getValue();}private static void copyFileToStream(File file, OutputStream out) throws IOException {//LOG.info("Downloading '" + FileUtil.getShortPath(file) + "' to " + status.getPlayer());final int bufferSize = 16 * 1024; // 16 KbitInputStream in = new BufferedInputStream(new FileInputStream(file), bufferSize);try {byte[] buf = new byte[bufferSize];long bitrateLimit = 0;long lastLimitCheck = 0;while (true) {long before = System.currentTimeMillis();int n = in.read(buf);if (n == -1) {break;}out.write(buf, 0, n);}} finally {out.flush();in.close();}}private static void zip(ZipOutputStream out, String root, File file) throws IOException {// Exclude all hidden files starting with a "."if (file.getName().startsWith(".")) {return;}String zipName = file.getCanonicalPath().substring(root.length() + 1);if (file.isFile()) {ZipEntry zipEntry = new ZipEntry(zipName);zipEntry.setSize(file.length());zipEntry.setCompressedSize(file.length());zipEntry.setCrc(computeCrc(file));out.putNextEntry(zipEntry);copyFileToStream(file, out);out.closeEntry();} else {ZipEntry zipEntry = new ZipEntry(zipName + '/');zipEntry.setSize(0);zipEntry.setCompressedSize(0);zipEntry.setCrc(0);out.putNextEntry(zipEntry);out.closeEntry();File[] children = file.listFiles(); //FileUtil.listFiles(file);for (File child : children) {zip(out, root, child);}}}public static void zipDir(String zipFileName, String dir) {try {File zipFile = new File(zipFileName);FileOutputStream fos = new FileOutputStream(zipFile);//ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(fos));CheckedOutputStream checksum = new CheckedOutputStream(fos, new CRC32());ZipOutputStream zos = new ZipOutputStream(checksum);File dirFile = new File(dir);String root = zipFile.getCanonicalPath().substring(0, zipFile.getCanonicalPath().length() - zipFile.getName().length() - 1);zip(zos, root, dirFile);} catch (IOException e) {e.printStackTrace();}}

但是上面的zip方法，压缩zip后，用Zip4J解压会失败，文件也有问题。这个后面来研究。

转自：

http://cxis.me/2018/03/03/%E4%B8%8A%E4%BC%A0Zip%E6%96%87%E4%BB%B6%E4%B8%8D%E8%A7%A3%E5%8E%8B%E8%AF%BB%E5%8F%96%E6%96%87%E4%BB%B6%E5%86%85%E5%AE%B9%E6%97%B6ZipEntry%E7%9A%84size%E4%B8%BA-1%E7%9A%84%E9%97%AE%E9%A2%98/