如何使用InputStream从ZIP读取文件？

Question

我必须使用SFTP从ZIP存档(只有一个文件,我知道它的名称)中获取文件内容.我唯一拥有的是ZIP InputStream.大多数示例显示如何使用此语句获取内容:

ZipFile zipFile = new ZipFile("location");

但正如我所说,我的本地机器上没有ZIP文件,我不想下载它.是否InputStream足以阅读？

UPD:这是我的方式:

import java.util.zip.ZipInputStream;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;

public class SFTP {


    public static void main(String[] args) {

        String SFTPHOST = "host";
        int SFTPPORT = 3232;
        String SFTPUSER = "user";
        String SFTPPASS = "mypass";
        String SFTPWORKINGDIR = "/dir/work";
        Session session = null;
        Channel channel = null;
        ChannelSftp channelSftp = null;
        try {
            JSch jsch = new JSch();
            session = jsch.getSession(SFTPUSER, SFTPHOST, SFTPPORT);
            session.setPassword(SFTPPASS);
            java.util.Properties config = new java.util.Properties();
            config.put("StrictHostKeyChecking", "no");
            session.setConfig(config);
            session.connect();
            channel = session.openChannel("sftp");
            channel.connect();
            channelSftp = (ChannelSftp) channel;
            channelSftp.cd(SFTPWORKINGDIR);
            ZipInputStream stream = new ZipInputStream(channelSftp.get("file.zip"));
            ZipEntry entry = zipStream.getNextEntry();
            System.out.println(entry.getName); //Yes, I got its name, now I need to get content
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            session.disconnect();
            channelSftp.disconnect();
            channel.disconnect();
        }


    }
}

Answer 1

下面是一个关于如何提取ZIP文件的简单示例,您需要检查该文件是否是目录.但这是最简单的.

您缺少的步骤是读取输入流并将内容写入写入输出流的缓冲区.

// Expands the zip file passed as argument 1, into the
// directory provided in argument 2
public static void main(String args[]) throws Exception
{
    if(args.length != 2)
    {
        System.err.println("zipreader zipfile outputdir");
        return;
    }

    // create a buffer to improve copy performance later.
    byte[] buffer = new byte[2048];

    // open the zip file stream
    InputStream theFile = new FileInputStream(args[0]);
    ZipInputStream stream = new ZipInputStream(theFile);
    String outdir = args[1];

    try
    {

        // now iterate through each item in the stream. The get next
        // entry call will return a ZipEntry for each file in the
        // stream
        ZipEntry entry;
        while((entry = stream.getNextEntry())!=null)
        {
            String s = String.format("Entry: %s len %d added %TD",
                            entry.getName(), entry.getSize(),
                            new Date(entry.getTime()));
            System.out.println(s);

            // Once we get the entry from the stream, the stream is
            // positioned read to read the raw data, and we keep
            // reading until read returns 0 or less.
            String outpath = outdir + "/" + entry.getName();
            FileOutputStream output = null;
            try
            {
                output = new FileOutputStream(outpath);
                int len = 0;
                while ((len = stream.read(buffer)) > 0)
                {
                    output.write(buffer, 0, len);
                }
            }
            finally
            {
                // we must always close the output file
                if(output!=null) output.close();
            }
        }
    }
    finally
    {
        // we must always close the zip file.
        stream.close();
    }
}

代码摘录来自以下网站:

http://www.thecoderscorner.com/team-blog/java-and-jvm/12-reading-a-zip-file-from-java-using-zipinputstream#.U4RAxYamixR

Answer 2

好吧,我做到了这个:

 zipStream = new ZipInputStream(channelSftp.get("Port_Increment_201405261400_2251.zip"));
 zipStream.getNextEntry();

 sc = new Scanner(zipStream);
 while (sc.hasNextLine()) {
     System.out.println(sc.nextLine());
 }

它帮助我阅读ZIP的内容,而无需写入另一个文件.

Answer 3

它ZipInputStream是一个InputStream单独的,并在每次调用后传递每个条目的内容getNextEntry().必须特别小心,不要关闭读取内容的流,因为它与ZIP流相同:

public void readZipStream(InputStream in) throws IOException {
    ZipInputStream zipIn = new ZipInputStream(in);
    ZipEntry entry;
    while ((entry = zipIn.getNextEntry()) != null) {
        System.out.println(entry.getName());
        readContents(zipIn);
        zipIn.closeEntry();
    }
}

private void readContents(InputStream contentsIn) throws IOException {
    byte contents[] = new byte[4096];
    int direct;
    while ((direct = contentsIn.read(contents, 0, contents.length)) >= 0) {
        System.out.println("Read " + direct + "bytes content.");
    }
}

将读取内容委托给其他逻辑时,可能需要ZipInputStream用a 包装 FilterInputStream来仅关闭条目而不是整个流,如下所示:

public void readZipStream(InputStream in) throws IOException {
    ZipInputStream zipIn = new ZipInputStream(in);
    ZipEntry entry;
    while ((entry = zipIn.getNextEntry()) != null) {
        System.out.println(entry.getName());

        readContents(new FilterInputStream(zipIn) {
            @Override
            public void close() throws IOException {
                zipIn.closeEntry();
            }
        });
    }
}

Answer 4

OP 很接近。只需要读取字节即可。对 getNextEntry 的调用positions the stream at the beginning of the entry data（文档）。如果这是我们想要的条目（或唯一的条目），那么 InputStream 就位于正确的位置。我们需要做的就是读取该条目的解压缩字节。

byte[] bytes = new byte[(int) entry.getSize()];
int i = 0;
while (i < bytes.length) {
    // .read doesn't always fill the buffer we give it.
    // Keep calling it until we get all the bytes for this entry.
    i += zipStream.read(bytes, i, bytes.length - i);
}

因此，如果这些字节确实是文本，那么我们可以将这些字节解码为字符串。我只是假设 utf8 编码。

new String(bytes, "utf8")

旁注：我个人使用 apache commons-io IOUtils来减少这种较低级别的东西。ZipInputStream.read 的文档似乎暗示读取将在当前 zip 条目的末尾停止。如果这是真的，那么用 IOUtils 读取当前的文本条目就是一行。

String text = IOUtils.toString(zipStream)