java.io.UTFDataFormatException 正在读取文件条目名称

Question

我正在尝试使用 DataInputStream / DataOutputStream 在另一个非 jar 文件中“打包”多个文件（以前在 jar 存档中）。

当时的想法是：

    First int = number of entries
    
    First UTF is the first entry name
    
    Second Int is entry byte array length (entry size)

    Then repeat for every entry.

代码：

 public static void main(String[] args) throws Throwable {
        test();

        System.out.println("========================================================================================");

        final DataInputStream dataInputStream = new DataInputStream(new FileInputStream(new File("C:\Users\Admin\Desktop\randomJarOut")));

        for (int int1 = dataInputStream.readInt(), i = 0; i < int1; ++i) {
            final String utf = dataInputStream.readUTF();
            System.out.println("Entry name: " + utf);
            final byte[] array = new byte[dataInputStream.readInt()];
            for (int j = 0; j < array.length; ++j) {
                array[j] = dataInputStream.readByte();
            }
            System.out.println("Entry bytes length: " + array.length);
        }

    }

拆开原始包装并包装成新包装：

private static void test() throws Throwable {
    JarInputStream stream = new JarInputStream(new FileInputStream(new File("C:\Users\Admin\Desktop\randomJar.jar")));
    JarInputStream stream1 = new JarInputStream(new FileInputStream(new File("C:\Users\Admin\Desktop\randomJar.jar")));

    final byte[] buffer = new byte[2048];
    final DataOutputStream outputStream = new DataOutputStream(new FileOutputStream(new File("C:\Users\Admin\Desktop\randomJarOut")));

    int entryCount = 0;
    for (ZipEntry entry; (entry = stream.getNextJarEntry()) != null; ) {
        entryCount++;
    }

    outputStream.writeInt(entryCount);

    for (JarEntry entry; (entry = stream1.getNextJarEntry()) != null; ) {
        int entryRealSize = stream1.read(buffer);
        if (!(entryRealSize == -1)) {
            System.out.println("Writing: " + entry.getName() + " Length: " + entryRealSize);

            outputStream.writeUTF(entry.getName());
            outputStream.writeInt(entryRealSize);

            for (int len = stream1.read(buffer); len != -1; len = stream1.read(buffer)) {
                outputStream.write(buffer, 0, len);
            }
        }
    }
    outputStream.flush();
    outputStream.close();
}

显然我能够毫无问题地解压第一个条目，第二个和其他条目：

Entry name: META-INF/services/org.jd.gui.spi.ContainerFactory
Entry bytes length: 434
Exception in thread "main" java.io.UTFDataFormatException: malformed input around byte 279
    at java.io.DataInputStream.readUTF(DataInputStream.java:656)
    at java.io.DataInputStream.readUTF(DataInputStream.java:564)
    at it.princekin.esercizio.Bootstrap.main(Bootstrap.java:29)
Disconnected from the target VM, address: '127.0.0.1:54384', transport: 'socket'

Process finished with exit code 1

有谁知道如何解决这个问题？为什么这适用于第一个条目而不适用于其他条目？

Answer 1

问题可能在于您混合的不是互惠 read/write 方法：

writer方法用outputStream.writeInt(entryCount)写入，main方法用dataInputStream.readInt()读取。没关系。
writer方法用outputStream.writeUTF(entry.getName())写入，main方法用dataInputStream.readUTF()读取。没关系。
writer方法用outputStream.writeInt(entryRealSize)写入，main方法用dataInputStream.readInt()读取。没关系。
writer方法用outputStream.write(buffer, 0, len)写，main方法用dataInputStream.readByte()读几次。错误。

如果用 write(buffer, offset, len) 写入一个字节数组，则必须用 read(buffer, offset, len) 读取它，因为 write(buffer, offset, len) 恰好将 len 个物理字节写入输出流，而 writeByte（readByte 的对应部分）写了很多关于对象类型的元数据开销，然后是它的状态变量。

writer 方法中的错误

writer 方法还有一个主要错误：它最多调用三次stream1.read(buffer)，但只使用一次buffer 内容。结果是文件的实际大小实际上写入了输出流元数据，但后面只有一小部分数据。

如果在将输入文件写入输出流之前需要知道输入文件的大小，您有两种选择：

要么选择足够大的缓冲区大小（例如 204800），这样您就可以在 一次读取 中读取整个文件，并在 一次写入中写。
或者将读取算法与写入算法分开：首先是读取整个文件并将其存储在内存中的方法（例如 byte[]），然后是将 byte[] 写入输出流的另一种方法.

全固定解

我已经修复了你的程序，每个任务都有特定的、解耦的方法。该过程包括将输入文件解析为内存模型，根据您的自定义定义将其写入中间文件，然后再读回。

public static void main(String[] args)
    throws Throwable
{
    File inputJarFile=new File(args[0]);
    File intermediateFile=new File(args[1]);
    List<FileData> fileDataEntries=parse(inputJarFile);
    write(fileDataEntries, intermediateFile);
    read(intermediateFile);
}

public static List<FileData> parse(File inputJarFile)
    throws IOException
{
    List<FileData> list=new ArrayList<>();
    try (JarInputStream stream=new JarInputStream(new FileInputStream(inputJarFile)))
    {
        for (ZipEntry entry; (entry=stream.getNextJarEntry()) != null;)
        {
            byte[] data=readAllBytes(stream);
            if (data.length > 0)
            {
                list.add(new FileData(entry.getName(), data));
            }
            stream.closeEntry();
        }
    }
    return list;
}

public static void write(List<FileData> fileDataEntries, File output)
    throws Throwable
{
    try (DataOutputStream outputStream=new DataOutputStream(new FileOutputStream(output)))
    {
        int entryCount=fileDataEntries.size();

        outputStream.writeInt(entryCount);

        for (FileData fileData : fileDataEntries)
        {
            int entryRealSize=fileData.getData().length;
            {
                System.out.println("Writing: " + fileData.getName() + " Length: " + entryRealSize);

                outputStream.writeUTF(fileData.getName());
                outputStream.writeInt(entryRealSize);
                outputStream.write(fileData.getData());
            }
        }
        outputStream.flush();
    }
}

public static void read(File intermediateFile)
    throws IOException
{
    try (DataInputStream dataInputStream=new DataInputStream(new FileInputStream(intermediateFile)))
    {
        for (int entryCount=dataInputStream.readInt(), i=0; i < entryCount; i++)
        {
            String utf=dataInputStream.readUTF();
            int entrySize=dataInputStream.readInt();
            System.out.println("Entry name: " + utf + " size: " + entrySize);
            byte[] data=readFixedLengthBuffer(dataInputStream, entrySize);
            System.out.println("Entry bytes length: " + data.length);
        }
    }
}

private static byte[] readAllBytes(InputStream input)
    throws IOException
{
    byte[] buffer=new byte[4096];
    byte[] total=new byte[0];
    int len;
    do
    {
        len=input.read(buffer);
        if (len > 0)
        {
            byte[] total0=total;
            total=new byte[total0.length + len];
            System.arraycopy(total0, 0, total, 0, total0.length);
            System.arraycopy(buffer, 0, total, total0.length, len);
        }
    }
    while (len >= 0);
    return total;
}

private static byte[] readFixedLengthBuffer(InputStream input, int size)
    throws IOException
{
    byte[] buffer=new byte[size];
    int pos=0;
    int len;
    do
    {
        len=input.read(buffer, pos, size - pos);
        if (len > 0)
        {
            pos+=len;
        }
    }
    while (pos < size);
    return buffer;
}

private static class FileData
{
    private final String name;

    private final byte[] data;

    public FileData(String name, byte[] data)
    {
        super();
        this.name=name;
        this.data=data;
    }

    public String getName()
    {
        return this.name;
    }

    public byte[] getData()
    {
        return this.data;
    }
}

Answer 2

我对此的看法是 jar 文件（实际上是一个 zip 文件）有一个 Central Directory，它只能用 ZipFile（或 JarFile）class 读取。中央目录包含有关条目的一些数据，例如大小。

我认为 ZipInputStream 不会读取中央目录，因此 ZipEntry 不会包含大小（返回 -1，因为它是未知的），而从 ZipFile class 读取 ZipEntry 会。

因此，如果您首先使用 ZipFile 读取每个条目的大小并将其存储在地图中，则在使用 ZipInputStream 读取数据时可以轻松获取它。

This page 也包括一些很好的例子。

所以我的代码版本是：

import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;

public class JarRepacker {

    public static void main(String[] args) throws Throwable {
        JarRepacker repacker = new JarRepacker();
        repacker.repackJarToMyFileFormat("commons-cli-1.3.1.jar", "randomJarOut.bin");
        repacker.readMyFileFormat("randomJarOut.bin");
    }
    
    private void repackJarToMyFileFormat(String inputJar, String outputFile) throws Throwable {
        int entryCount;
        Map<String, Integer> sizeMap = new HashMap<>();
        try (ZipFile zipFile = new ZipFile(inputJar)) {
            entryCount = zipFile.size();
            zipFile.entries().asIterator().forEachRemaining(e -> sizeMap.put(e.getName(), (int) e.getSize()));
        }

        try (final DataOutputStream outputStream = new DataOutputStream(new FileOutputStream(outputFile))) {

            outputStream.writeInt(entryCount);

            try (ZipInputStream stream = new ZipInputStream(new BufferedInputStream(new FileInputStream(inputJar)))) {
                ZipEntry entry;
                final byte[] buffer = new byte[2048];
                while ((entry = stream.getNextEntry()) != null) {
                    final String name = entry.getName();
                    outputStream.writeUTF(name);
                    final Integer size = sizeMap.get(name);
                    outputStream.writeInt(size);
                    //System.out.println("Writing: " + name + " Size: " + size);

                    int len;
                    while ((len = stream.read(buffer)) > 0) {
                        outputStream.write(buffer, 0, len);
                    }
                }
            }
            outputStream.flush();
        }
    }

    private void readMyFileFormat(String fileToRead) throws IOException {
        try (DataInputStream dataInputStream
                     = new DataInputStream(new BufferedInputStream(new FileInputStream(fileToRead)))) {

            int entries = dataInputStream.readInt();
            System.out.println("Entries in file: " + entries);
            for (int i = 1; i <= entries; i++) {
                final String name = dataInputStream.readUTF();
                final int size = dataInputStream.readInt();
                System.out.printf("[%3d] Reading: %s of size: %d%n", i, name, size);
                final byte[] array = new byte[size];
                for (int j = 0; j < array.length; ++j) {
                    array[j] = dataInputStream.readByte();
                }
                // Still need to do something with this array...
            }
        }
    }

}

java.io.UTFDataFormatException 正在读取文件条目名称

java.io.UTFDataFormatException while reading file entry name

java

file

packing

offset

datainputstream

writer 方法中的错误

全固定解