如何将 zip 文件读取为字节数组，然后将字节数组转换回 zip 文件？

Question

我曾尝试使用此代码将 ZIP 文件转换为字节数组：

private static byte[] readZipFile(String zipFnm)
// read in fnm, returning it as a single string
{

  FileInputStream fileInputStream=null;

  File file = new File(zipFnm);

  byte[] bFile = new byte[(int) file.length()];

  try{
    //convert file into array of bytes
    fileInputStream = new FileInputStream(zipFnm);
    fileInputStream.read(bFile);
    fileInputStream.close();
  }catch(Exception e){
    e.printStackTrace();
  }
  return bFile;
}  

以及用于将字节数组转换回 ZIP 的代码，通过调用 writeByteToZip(fnm + ".zip");

private static String writeByteToZip(String outFnm)
{
  try {
    FileOutputStream fileOuputStream = new FileOutputStream(outFnm); 
    fileOuputStream.write(bFile);
    fileOuputStream.close();            

  } catch ( IOException iox ){
    iox.printStackTrace();
  }
  return outFnm;
}  // end of writeByteToZip()

我究竟做错了什么？我使用正确的 zip 字节长度

byte[] bzip = readZipFile(zipFnm);

int totalLen1 = bzip.length;
System.out.println("Total byte length of zip: " + totalLen1);

我得到的只是一个零大小的 zip 文件和 Netbeans 中的运行时错误：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at java.io.FileOutputStream.write(FileOutputStream.java:305)
    at steg.Steg.writeByteToZip(Steg.java:402)
    at steg.Steg.save(Steg.java:292)
    at steg.frame1.jButton2ActionPerformed(frame1.java:349)
    at steg.frame1.access$300(frame1.java:24)
    at steg.frame1$4.actionPerformed(frame1.java:172)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Answer 1

bFile您提供的堆栈跟踪将由于为空而导致。

原因可能是您的readZipFile方法中的以下行：

byte[] bFile = new byte[(int) file.length()];

这里你分配给一个局部变量，而不是你的类字段。尝试将该行替换为：

bFile = new byte[file.length()];

您的代码还表明资源处理很差。使用现有的库方法进行阅读（例如commons-io或 Java 7 Files）或编写代码，例如：

FileInputStream fileInputStream = null;
try {
  fileInputStream = new //...
} finally {
  if (fileInputStream != null) {
    fileInputStream.close();
  }
}

如果您有 Java 7，则可以使用 try-with-resources：

try (FileInputStream fileInputStream = new FileInputStream(zipFnm)) {
  // Use your stream
}