Java 临时用 zip4j 解压文件。（提取读取但在缓存文件中不可见）

extracting files with zip4j temporarily. (Extracted for reading but not visible in cache file)

提问by Ryan

I am working with zip4j & packing & extracting work but i'm curious on how to just extract the file without putting the files in the cache.

我正在使用 zip4j 和打包和提取工作，但我很好奇如何只提取文件而不将文件放入缓存中。

Here is some code i found on another thread:

这是我在另一个线程上找到的一些代码：

public static void main() {
    String source = "C:\Users\gamecaching\Cache.zip";
    String destination = "C:\Users\gamecaching\";
    String password = "mypassword";

    try {
        ZipFile zipFile = new ZipFile(source);
        if (zipFile.isEncrypted()) {
            zipFile.setPassword(password);
        }
        zipFile.extractAll(destination);
    } catch (ZipException e) {
        e.printStackTrace();
    }
}

How do I get it to only extract while the program is running(&& extracted files not visible in directory) & delete after the program has exited.

如何让它仅在程序运行时提取（&& 提取的文件在目录中不可见）并在程序退出后删除。

采纳答案by Srikanth Reddy Lingala

After you create a ZipFile

创建 ZipFile 后

ZipFile zipFile = new ZipFile(source);

you can loop through each File in the zip file like this:

您可以像这样遍历 zip 文件中的每个文件：

ArrayList fileHeaderList = zipFile.getFileHeaders();

For each ZipFile:

对于每个 ZipFile：

for (int i = 0; i < fileHeaderList.size(); i++) {
    FileHeader fileHeader = (FileHeader)fileHeaderList.get(i);

Then, you can get the inputStream by doing this

然后，您可以通过执行此操作获取 inputStream

is = zipFile.getInputStream(fileHeader);

Now you have the InputStream to read from.

现在您有了要读取的 InputStream。

A comprehensive example to work with Streams is below (taken from Zip4j examples package.) Although this example still writes to a file, but it demonstrates the use of streams with the zip file. I suggest having a look at a few more examples in the examples package.

下面是一个使用 Streams 的综合示例（取自Zip4j 示例包。）虽然这个示例仍然写入文件，但它演示了 zip 文件中流的使用。我建议在 examples 包中查看更多示例。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;

import net.lingala.zip4j.core.ZipFile;
import net.lingala.zip4j.exception.ZipException;
import net.lingala.zip4j.io.ZipInputStream;
import net.lingala.zip4j.model.FileHeader;
import net.lingala.zip4j.unzip.UnzipUtil;

/**
 * Example demonstrating the use of InputStreams to extract files from the
 * ZipFile
 */
public class ExtractAllFilesWithInputStreams {

    private final int BUFF_SIZE = 4096;

    public ExtractAllFilesWithInputStreams() {
        ZipInputStream is = null;
        OutputStream os = null;
        try {
            // Initiate the ZipFile
            ZipFile zipFile = new ZipFile(
                "C:\ZipTest\ExtractAllFilesWithInputStreams.zip");
            String destinationPath = "c:\ZipTest";
            // If zip file is password protected then set the password
            if (zipFile.isEncrypted()) {
                zipFile.setPassword("password");
            }
            // Get a list of FileHeader. FileHeader is the header information
            // for all the files in the ZipFile
            List fileHeaderList = zipFile.getFileHeaders();
            // Loop through all the fileHeaders
            for (int i = 0; i < fileHeaderList.size(); i++) {
                FileHeader fileHeader = (FileHeader) fileHeaderList.get(i);
                if (fileHeader != null) {
                    // Build the output file
                    String outFilePath = destinationPath
                        + System.getProperty("file.separator")
                        + fileHeader.getFileName();
                    File outFile = new File(outFilePath);
                    // Checks if the file is a directory
                    if (fileHeader.isDirectory()) {
                        // This functionality is up to your requirements
                        // For now I create the directory
                        outFile.mkdirs();
                        continue;
                    }
                    // Check if the directories(including parent directories)
                    // in the output file path exists
                    File parentDir = outFile.getParentFile();
                    if (!parentDir.exists()) {
                        parentDir.mkdirs();
                    }
                    // Get the InputStream from the ZipFile
                    is = zipFile.getInputStream(fileHeader);
                    // Initialize the output stream
                    os = new FileOutputStream(outFile);
                    int readLen = -1;
                    byte[] buff = new byte[BUFF_SIZE];
                    // Loop until End of File and write the contents to the
                    // output stream
                    while ((readLen = is.read(buff)) != -1) {
                        os.write(buff, 0, readLen);
                    }
                    // Please have a look into this method for some important
                    // comments
                    closeFileHandlers(is, os);
                    // To restore File attributes (ex: last modified file time,
                    // read only flag, etc) of the extracted file, a utility
                    // class can be used as shown below
                    UnzipUtil.applyFileAttributes(fileHeader, outFile);
                    System.out.println("Done extracting: "
                        + fileHeader.getFileName());
                } else {
                    System.err.println("fileheader is null. Shouldn't be here");
                }
            }
        } catch (ZipException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                closeFileHandlers(is, os);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void closeFileHandlers(ZipInputStream is, OutputStream os)
            throws IOException {
        // Close output stream
        if (os != null) {
            os.close();
            os = null;
        }
        // Closing inputstream also checks for CRC of the the just extracted
        // file. If CRC check has to be skipped (for ex: to cancel the unzip
        // operation, etc) use method is.close(boolean skipCRCCheck) and set the
        // flag, skipCRCCheck to false
        // NOTE: It is recommended to close outputStream first because Zip4j
        // throws an exception if CRC check fails
        if (is != null) {
            is.close();
            is = null;
        }
    }

    public static void main(String[] args) {
        new ExtractAllFilesWithInputStreams();
    }
}

回答by agad

To read a concrete entry of a zip file use: zipFile.getInputStream(FileHeader). To read all entries:

要读取 zip 文件的具体条目，请使用：zipFile.getInputStream(FileHeader). 要阅读所有条目：

for (FileHeader entry: zipFile:getFileHeaders()){
    zipFile.getInputStream(FileHeader);
}

回答by SubOptimal

an example derived from ExtractAllFilesWithInputStreams:

从 ExtractAllFilesWithInputStreams 派生的示例：

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import net.lingala.zip4j.core.ZipFile;
import net.lingala.zip4j.exception.ZipException;
import net.lingala.zip4j.io.ZipInputStream;
import net.lingala.zip4j.model.FileHeader;

public class StackoverFlow18974389 {

    public static void main(String[] args) {
        Map<String, InputStream> inMemoryFiles = new HashMap<>();
        try {
            ZipFile zipFile = new ZipFile("test.zip");
            List fileHeaderList = zipFile.getFileHeaders();
            for (int i = 0; i < fileHeaderList.size(); i++) {
                FileHeader fileHeader = (FileHeader) fileHeaderList.get(i);
                ZipInputStream is = zipFile.getInputStream(fileHeader);
                int uncompressedSize = (int) fileHeader.getUncompressedSize();
                OutputStream os = new ByteArrayOutputStream(uncompressedSize);
                int bytesRead;
                byte[] buffer = new byte[4096];
                while ((bytesRead = is.read(buffer)) != -1) {
                    os.write(buffer, 0, bytesRead);
                }
                byte[] uncompressedBytes = ((ByteArrayOutputStream) os).toByteArray();
                inMemoryFiles.put(fileHeader.getFileName(), new ByteArrayInputStream(uncompressedBytes));
                is.close();
            }
        } catch (ZipException | IOException ex) {
            ex.printStackTrace(System.err);
        }
        // very simple example how to access the files from the map
        for (String fileName : inMemoryFiles.keySet()) {
            System.out.print("in memory file: " + fileName);
            InputStream is = new BufferedInputStream(inMemoryFiles.get(fileName));
            long length = 0;
            try {
                while (is.read() != -1) {
                    length++;
                }
            } catch (IOException ex) {
                ex.printStackTrace(System.err);
            }
            System.out.println(" size. " + length);
        }
    }
}

回答by mvanle

When doing a Google search on "test zip file zip4j" I got to this thread, so decided to use the existing examples by people to create a method to test zip files. Maybe it will be useful:

在对“测试 zip 文件 zip4j”进行 Google 搜索时，我找到了这个线程，因此决定使用人们现有的示例来创建一种测试 zip 文件的方法。也许它会很有用：

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;

import net.lingala.zip4j.core.ZipFile;
import net.lingala.zip4j.exception.ZipException;
import net.lingala.zip4j.io.ZipInputStream;
import net.lingala.zip4j.model.FileHeader;

import org.apache.commons.io.output.NullOutputStream;

/**
 * Example demonstrating testing Zip files using net.lingala.zip4j
 * 
 * Changes: 
 *      - Created static method testZipFile
 *      - Uses Buffered IO
 *      - Uses Apache Commons' NullOutputStream() for /dev/null
 *      - Uses enhanced for loop
 *      - Skip CRC check
 *      - Removed unapplicable code
 */
public class Zip4jTestZipFile
{
    public static void main(String[] args)
    {
        File zipfile = new File("D:\JDeveloper\mywork\Gas_Market_Systems\GMS-FLISTCopy\test\inetpub\tmp.lem\FLIST_COUNTRYNWO_20140411.zip");
        testZipFile(zipfile);
    }

    /* Adapted from SrikanthLingala's answer (http://stackoverflow.com/a/18974782/1213722) */
    public static void testZipFile(File zipfile) {
        ZipInputStream is = null;
        OutputStream os = new NullOutputStream();   // org.apache.commons.io.output.NullOutputStream

        /* Buffered IO */
        BufferedInputStream bis = null;
        BufferedOutputStream bos = new BufferedOutputStream(os);

        try {
            // Initiate the ZipFile
            ZipFile zipFile = new ZipFile(zipfile);
            // If zip file is password protected then set the password
            if (zipFile.isEncrypted()) {
                zipFile.setPassword("password");
            }
            // Get a list of FileHeader. FileHeader is the header information
            // for all the files in the ZipFile
            List<FileHeader> fileHeaderList = zipFile.getFileHeaders();
            // Loop through all the fileHeaders
            for (FileHeader fileHeader : fileHeaderList) {
                if (fileHeader != null) {

                    // Removed: Build the output file
                    // Removed: directory checks
                    // Removed: parent directory checks

                    // Get the InputStream from the ZipFile
                    is = zipFile.getInputStream(fileHeader);
                    bis = new BufferedInputStream(is);

                    // Removed: Initialize the output stream

                    int readLen = -1;
                    // Loop until End of File and write the contents to the
                    // output stream
                    while ((readLen = bis.read()) != -1)
                    {
                        bos.write(readLen);
                    }

                    // Please have a look into this method for some important
                    // comments
                    closeFileHandlers(is, os);

                    // Removed: restore File attributes

                    System.out.println("Done testing: "
                        + fileHeader.getFileName());
                } else {
                    System.err.println("fileheader is null. Shouldn't be here");
                }
            }
        } catch (ZipException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                closeFileHandlers(is, os);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static void closeFileHandlers(ZipInputStream is, OutputStream os)
            throws IOException {
        // Close output stream
        if (os != null) {
            os.close();
            os = null;
        }

        // Closing inputstream also checks for CRC of the the just extracted
        // file. If CRC check has to be skipped (for ex: to cancel the unzip
        // operation, etc) use method is.close(boolean skipCRCCheck) and set the
        // flag, skipCRCCheck to false
        // NOTE: It is recommended to close outputStream first because Zip4j
        // throws an exception if CRC check fails
        if (is != null) {
//            is.close();
            boolean skipCRCCheck = false;
            is.close(skipCRCCheck);
            is = null;
        }
    }
}