org.apache.commons.io.IOUtils IOUtils.copy与IOUtils.closeQuietly的用法

org.apache.commons.io.IOUtils IOUtils.copy与IOUtils.closeQuietly的用法

2012年10月05日 17:11:25

阅读数：9691

byte[] data = new byte[1024];
InputStream in = null;
OutputStream out = null;

try {
      in = new FileInputStream("foo.txt");
      in.read(data);

      out = new FileOutputStream("foo.txt");
      data = "Hello, World".getBytes();
      out.write(data);

      //将OutputStream复制到InputStream大文件(超过2GB),这个方法已经使用了缓存,所以不再需要缓存 如果文件大小超过2GB,则返回-1
      IOUtils.copy(in, out);

      in.close(); //close errors are handled
      out.close();
    } catch (IOException e) {
      // error handling
    } finally {
      IOUtils.closeQuietly(in);
      IOUtils.closeQuietly(out);
}

org.apache.commons.io.IOUtils  API

org.apache.commons.io
Class IOUtils

General IO stream manipulation utilities.

This class provides static utility methods for input/output operations.

• closeQuietly - these methods close a stream ignoring nulls and exceptions
• toXxx/read - these methods read data from a stream
• write - these methods write data to a stream
• copy - these methods copy all the data from one stream to another
• contentEquals - these methods compare the content of two streams

The byte-to-char methods and char-to-byte methods involve a conversion step. Two methods are provided in each case, one that uses the platform default encoding and the other which allows you to specify an encoding. You are encouraged to always specify an encoding because relying on the platform default can lead to unexpected results, for example when moving from development to production.

All the methods in this class that read a stream are buffered internally. This means that there is no cause to use a BufferedInputStream or BufferedReader. The default buffer size of 4K has been shown to be efficient in tests.

Wherever possible, the methods in this class do not flush or close the stream. This is to avoid making non-portable assumptions about the streams' origin and further use. Thus the caller is still responsible for closing streams after use.

copy

public static int copy(InputStream input,
                       OutputStream output)
                throws IOException

Copy bytes from an InputStream to an OutputStream.

This method buffers the input internally, so there is no need to use a BufferedInputStream.

Large streams (over 2GB) will return a bytes copied value of -1 after the copy has completed since the correct number of bytes cannot be returned as an int. For large streams use the copyLarge(InputStream, OutputStream) method.

Parameters:

input - the InputStream to read from

output - the OutputStream to write to

Returns:

the number of bytes copied, or -1 if > Integer.MAX_VALUE

Throws:

NullPointerException - if the input or output is null

IOException - if an I/O error occurs

Since:

Commons IO 1.1

closeQuietly

public static void closeQuietly(InputStream input)

Unconditionally close an InputStream.

Equivalent to InputStream.close(), except any exceptions will be ignored. This is typically used in finally blocks.

Example code:

   byte[] data = new byte[1024];
   InputStream in = null;
   try {
       in = new FileInputStream("foo.txt");
       in.read(data);
       in.close(); //close errors are handled
   } catch (Exception e) {
       // error handling
   } finally {
       IOUtils.closeQuietly(in);
   }
 

Parameters:

input - the InputStream to close, may be null or already closed

closeQuietly

public static void closeQuietly(OutputStream output)

Unconditionally close an OutputStream.

Equivalent to OutputStream.close(), except any exceptions will be ignored. This is typically used in finally blocks.

Example code:

 byte[] data = "Hello, World".getBytes();

 OutputStream out = null;
 try {
     out = new FileOutputStream("foo.txt");
     out.write(data);
     out.close(); //close errors are handled
 } catch (IOException e) {
     // error handling
 } finally {
     IOUtils.closeQuietly(out);
 }
 

Parameters:

output - the OutputStream to close, may be null or already closed