java.util.zip.ZipEntry.getExtra()方法示例

java.util.zip.ZipEntry.getExtra()方法返回條目的額外字段數據，如果沒有，則返回null。

聲明

以下是java.util.zip.ZipEntry.getExtra()方法的聲明。

public byte[] getExtra()

返回值

• 條目的額外字段數據，如果沒有，則返回null。

前提條件

在D:\test>目錄下用以下內容創建一個檔Hello.txt。

This is an example.

示例

以下示例顯示了java.util.zip.ZipEntry.getExtra()方法的用法。

package com.zaixian;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.Enumeration;
import java.util.zip.Adler32;
import java.util.zip.CheckedOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

public class ZipEntryDemo {
   private static String SOURCE_FILE = "D:\\test\\Hello.txt";
   private static String TARGET_FILE = "D:\\test\\Hello.zip";

   public static void main(String[] args) {
      try {
         createZipFile();
         readZipFile();
      } catch(IOException ioe) {
         System.out.println("IOException : " + ioe);
      }
   }

   private static void createZipFile() throws IOException{
      FileOutputStream fout = new FileOutputStream(TARGET_FILE);
      CheckedOutputStream checksum = new CheckedOutputStream(fout, new Adler32());
      ZipOutputStream zout = new ZipOutputStream(checksum);

      FileInputStream fin = new FileInputStream(SOURCE_FILE);
      ZipEntry zipEntry = new ZipEntry(SOURCE_FILE);
      zipEntry.setExtra("sample data".getBytes());
      zout.putNextEntry(zipEntry);
      int length;
      byte[] buffer = new byte[1024];
      while((length = fin.read(buffer)) > 0) {
         zout.write(buffer, 0, length);
      }

      zout.closeEntry();
      fin.close();
      zout.close();
   }

   private static void readZipFile() throws IOException{
      final ZipFile file = new ZipFile(TARGET_FILE);
      System.out.println("Iterating over zip file : " + TARGET_FILE);
      try {
         final Enumeration<? extends ZipEntry> entries = file.entries();
         while (entries.hasMoreElements()) {
            final ZipEntry entry = entries.nextElement();
            System.out.printf("File: %s Size %d Modified on %TD %n",
               entry.getName(), entry.getSize(),
                  new Date(entry.getTime()));
            System.out.println(new String(entry.getExtra(), 0, entry.getExtra().length, "UTF-8"));
            extractFile(entry, file.getInputStream(entry));
         }
         System.out.printf("Zip file %s extracted successfully.", SOURCE_FILE);
      }
      finally {
         file.close();
      }
   }

   private static void extractFile(final ZipEntry entry, InputStream is)
      throws IOException {
      FileOutputStream fos = null;
      try {
         fos = new FileOutputStream(entry.getName());
         final byte[] buf = new byte[1024];
         int read = 0;
         int length;
         while ((length = is.read(buf, 0, buf.length)) >= 0) {
            fos.write(buf, 0, length);
         }
      } catch (IOException ioex) {
         fos.close();
      }
   }
}

讓我們編譯並運行上面的程式，這會產生以下結果 -

Iterating over zip file : D:\test\Hello.zip
File: D:\test\Hello.txt Size 19 Modified on 05/20/17
sample data
Zip file D:\test\Hello.txt extracted successfully.