Class IOUtils

java.lang.Object
org.apache.tomcat.util.http.fileupload.IOUtils
public class IOUtils extends Object
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.

Origin of code: Excalibur.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    EOF
    Represents the end-of-file (or stream).

  • Constructor Summary

    Constructors
    Constructor
    Description
    IOUtils()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    closeQuietly(Closeable closeable)
    Closes a Closeable unconditionally.
    static int
    copy(InputStream input, OutputStream output)
    Copies bytes from an InputStream to an OutputStream.
    static long
    copyLarge(InputStream input, OutputStream output)
    Copies bytes from a large (over 2GB) InputStream to an OutputStream.
    static int
    read(InputStream input, byte[] buffer, int offset, int length)
    Reads bytes from an input stream.
    static void
    readFully(InputStream input, byte[] buffer)
    Reads the requested number of bytes or fail if there are not enough left.
    static void
    readFully(InputStream input, byte[] buffer, int offset, int length)
    Reads the requested number of bytes or fail if there are not enough left.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • EOF

      public static final int EOF
      Represents the end-of-file (or stream).
      Since:
      IO 2.5 (made public)
      See Also:

  • Constructor Details

    • IOUtils

      public IOUtils()

  • Method Details

    • closeQuietly

      public static void closeQuietly(Closeable closeable)
      Closes a Closeable unconditionally.

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

      Example code: 

       Closeable closeable = null;
 try {
     closeable = new FileReader("foo.txt");
     // process closeable
     closeable.close();
 } catch (Exception e) {
     // error handling
 } finally {
     IOUtils.closeQuietly(closeable);
 }

      Closing all streams: 

       try {
     return IOUtils.copy(inputStream, outputStream);
 } finally {
     IOUtils.closeQuietly(inputStream);
     IOUtils.closeQuietly(outputStream);
 }
      Parameters:
      closeable - the objects to close, may be null or already closed
      Since:
      IO 2.0

    • copy

      public static int copy(InputStream input, OutputStream output) throws IOException
      Copies 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:
      IO 1.1

    • copyLarge

      public static long copyLarge(InputStream input, OutputStream output) throws IOException
      Copies bytes from a large (over 2GB) InputStream to an OutputStream.

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

      The buffer size is given by DEFAULT_BUFFER_SIZE.

      Parameters:
      input - the InputStream to read from
      output - the OutputStream to write to
      Returns:
      the number of bytes copied
      Throws:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      IO 1.3

    • read

      public static int read(InputStream input, byte[] buffer, int offset, int length) throws IOException
      Reads bytes from an input stream. This implementation guarantees that it will read as many bytes as possible before giving up; this may not always be the case for subclasses of InputStream.
      Parameters:
      input - where to read input from
      buffer - destination
      offset - initial offset into buffer
      length - length to read, must be >= 0
      Returns:
      actual length read; may be less than requested if EOF was reached
      Throws:
      IOException - if a read error occurs
      Since:
      IO 2.2

    • readFully

      public static void readFully(InputStream input, byte[] buffer, int offset, int length) throws IOException
      Reads the requested number of bytes or fail if there are not enough left.

      This allows for the possibility that InputStream.read(byte[], int, int) may not read as many bytes as requested (most likely because of reaching EOF).

      Parameters:
      input - where to read input from
      buffer - destination
      offset - initial offset into buffer
      length - length to read, must be >= 0
      Throws:
      IOException - if there is a problem reading the file
      IllegalArgumentException - if length is negative
      EOFException - if the number of bytes read was incorrect
      Since:
      IO 2.2

    • readFully

      public static void readFully(InputStream input, byte[] buffer) throws IOException
      Reads the requested number of bytes or fail if there are not enough left.

      This allows for the possibility that InputStream.read(byte[], int, int) may not read as many bytes as requested (most likely because of reaching EOF).

      Parameters:
      input - where to read input from
      buffer - destination
      Throws:
      IOException - if there is a problem reading the file
      IllegalArgumentException - if length is negative
      EOFException - if the number of bytes read was incorrect
      Since:
      IO 2.2