Package org.apache.tomcat.util.http.fileupload

Class IOUtils

  • public class IOUtils
extends java.lang.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 int EOF
      Represents the end-of-file (or stream).

    • Constructor Summary

      Constructors 
      Constructor Description
      IOUtils()  

    • Method Summary

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

      • EOF

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

    • Constructor Detail

      • IOUtils

        public IOUtils()

    • Method Detail

      • closeQuietly

        public static void closeQuietly​(java.io.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:
        2.0

      • copy

        public static int copy​(java.io.InputStream input,
                       java.io.OutputStream output)
                throws java.io.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:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.1

      • copyLarge

        public static long copyLarge​(java.io.InputStream input,
                             java.io.OutputStream output)
                      throws java.io.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:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.3

      • read

        public static int read​(java.io.InputStream input,
                       byte[] buffer,
                       int offset,
                       int length)
                throws java.io.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:
        java.io.IOException - if a read error occurs
        Since:
        2.2

      • readFully

        public static void readFully​(java.io.InputStream input,
                             byte[] buffer,
                             int offset,
                             int length)
                      throws java.io.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:
        java.io.IOException - if there is a problem reading the file
        java.lang.IllegalArgumentException - if length is negative
        java.io.EOFException - if the number of bytes read was incorrect
        Since:
        2.2

      • readFully

        public static void readFully​(java.io.InputStream input,
                             byte[] buffer)
                      throws java.io.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:
        java.io.IOException - if there is a problem reading the file
        java.lang.IllegalArgumentException - if length is negative
        java.io.EOFException - if the number of bytes read was incorrect
        Since:
        2.2