byte[] getExtra()

描述 (Description)

java.util.zip.ZipEntry.getExtra()方法返回条目的额外字段数据，如果没有，则返回null。

声明 (Declaration)

以下是java.util.zip.ZipEntry.getExtra()方法的声明。

public byte[] getExtra()

返回值 (Returns)

条目的额外字段数据，如果没有则为null。

先决条件

在D:》 test 》目录中创建一个文件Hello.txt，其中包含以下内容。

This is an example.

例子 (Example)

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

package cn.xnip;
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(); 
      } 
   }
}

让我们编译并运行上面的程序，这将产生以下结果 -

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.