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java.lang.Objectorg.apache.commons.io.IOUtils
General IO Stream manipulation.
This class provides static utility methods for input/output operations, particularly buffered
copying between sources (InputStream
, Reader
, String
and
byte[]
) and destinations (OutputStream
, Writer
,
String
and byte[]
).
Unless otherwise noted, these copy
methods do not flush or close the
streams. Often, doing so would require making non-portable assumptions about the streams' origin
and further use. This means that both streams' close()
methods must be called after
copying. if one omits this step, then the stream resources (sockets, file descriptors) are
released when the associated Stream is garbage-collected. It is not a good idea to rely on this
mechanism. For a good overview of the distinction between "memory management" and "resource
management", see this
UnixReview article
For byte-to-char methods, a copy
variant allows the encoding
to be selected (otherwise the platform default is used). We would like to
encourage you to always specify the encoding because relying on the platform
default can lead to unexpected results.
We don't provide special variants for the copy
methods that
let you specify the buffer size because in modern VMs the impact on speed
seems to be minimal. We're using a default buffer size of 4 KB.
The copy
methods use an internal buffer when copying. It is therefore advisable
not to deliberately wrap the stream arguments to the copy
methods in
Buffered*
streams. For example, don't do the
following:
copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
The rationale is as follows:
Imagine that an InputStream's read() is a very expensive operation, which would usually suggest
wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent
InputStream.read(byte[] b, int off, int len)
requests on the underlying InputStream, to
fill an internal buffer, from which further read
requests can inexpensively get
their data (until the buffer runs out).
However, the copy
methods do the same thing, keeping an internal buffer,
populated by InputStream.read(byte[] b, int off, int len)
requests. Having two buffers
(or three if the destination stream is also buffered) is pointless, and the unnecessary buffer
management hurts performance slightly (about 3%, according to some simple experiments).
Behold, intrepid explorers; a map of this class:
Method Input Output Dependency ------ ----- ------ ------- 1 copy InputStream OutputStream (primitive) 2 copy Reader Writer (primitive) 3 copy InputStream Writer 2 4 toString InputStream String 3 5 toByteArray InputStream byte[] 1 6 copy Reader OutputStream 2 7 toString Reader String 2 8 toByteArray Reader byte[] 6 9 copy String OutputStream 2 10 copy String Writer (trivial) 11 toByteArray String byte[] 9 12 copy byte[] Writer 3 13 toString byte[] String 12 14 copy byte[] OutputStream (trivial)
Note that only the first two methods shuffle bytes; the rest use these two, or (if possible) copy using native Java copy methods. As there are method variants to specify the encoding, each row may correspond to up to 2 methods.
Origin of code: Apache Avalon (Excalibur)
Field Summary | |
private static int |
DEFAULT_BUFFER_SIZE
|
Constructor Summary | |
IOUtils()
Instances should NOT be constructed in standard programming. |
Method Summary | |
static void |
closeQuietly(java.io.InputStream input)
Unconditionally close an InputStream . |
static void |
closeQuietly(java.io.OutputStream output)
Unconditionally close an OutputStream . |
static void |
closeQuietly(java.io.Reader input)
Unconditionally close an Reader . |
static void |
closeQuietly(java.io.Writer output)
Unconditionally close an Writer . |
static boolean |
contentEquals(java.io.InputStream input1,
java.io.InputStream input2)
Compare the contents of two Streams to determine if they are equal or not. |
static byte[] |
toByteArray(java.io.InputStream input)
Get the contents of an InputStream as a byte[] . |
static byte[] |
toByteArray(java.io.Reader input)
Get the contents of a Reader as a byte[] . |
static byte[] |
toByteArray(java.lang.String input)
Get the contents of a String as a byte[] . |
static java.lang.String |
toString(byte[] input)
Get the contents of a byte[] as a String. |
static java.lang.String |
toString(byte[] input,
java.lang.String encoding)
Get the contents of a byte[] as a String. |
static java.lang.String |
toString(java.io.InputStream input)
Get the contents of an InputStream as a String. |
static java.lang.String |
toString(java.io.InputStream input,
java.lang.String encoding)
Get the contents of an InputStream as a String. |
static java.lang.String |
toString(java.io.Reader input)
Get the contents of a Reader as a String. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
private static final int DEFAULT_BUFFER_SIZE
Constructor Detail |
public IOUtils()
Method Detail |
public static void closeQuietly(java.io.Reader input)
Reader
.
Equivalent to Reader.close()
, except any exceptions will be ignored.
input
- A (possibly null) Readerpublic static void closeQuietly(java.io.Writer output)
Writer
.
Equivalent to Writer.close()
, except any exceptions will be ignored.
output
- A (possibly null) Writerpublic static void closeQuietly(java.io.OutputStream output)
OutputStream
.
Equivalent to OutputStream.close()
, except any exceptions will be ignored.
output
- A (possibly null) OutputStreampublic static void closeQuietly(java.io.InputStream input)
InputStream
.
Equivalent to InputStream.close()
, except any exceptions will be ignored.
input
- A (possibly null) InputStreampublic static java.lang.String toString(java.io.InputStream input) throws java.io.IOException
InputStream
as a String.
The platform's default encoding is used for the byte-to-char conversion.
input
- the InputStream
to read from
String
java.io.IOException
- In case of an I/O problempublic static java.lang.String toString(java.io.InputStream input, java.lang.String encoding) throws java.io.IOException
InputStream
as a String.
input
- the InputStream
to read fromencoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
String
java.io.IOException
- In case of an I/O problempublic static byte[] toByteArray(java.io.InputStream input) throws java.io.IOException
InputStream
as a byte[]
.
input
- the InputStream
to read from
java.io.IOException
- In case of an I/O problempublic static java.lang.String toString(java.io.Reader input) throws java.io.IOException
Reader
as a String.
input
- the Reader
to read from
String
java.io.IOException
- In case of an I/O problempublic static byte[] toByteArray(java.io.Reader input) throws java.io.IOException
Reader
as a byte[]
.
input
- the Reader
to read from
java.io.IOException
- In case of an I/O problempublic static byte[] toByteArray(java.lang.String input) throws java.io.IOException
String
as a byte[]
.
input
- the String
to convert
java.io.IOException
- In case of an I/O problempublic static java.lang.String toString(byte[] input) throws java.io.IOException
byte[]
as a String.
The platform's default encoding is used for the byte-to-char conversion.
input
- the byte array to read from
String
java.io.IOException
- In case of an I/O problempublic static java.lang.String toString(byte[] input, java.lang.String encoding) throws java.io.IOException
byte[]
as a String.
input
- the byte array to read fromencoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
String
java.io.IOException
- In case of an I/O problempublic static boolean contentEquals(java.io.InputStream input1, java.io.InputStream input2) throws java.io.IOException
input1
- the first streaminput2
- the second stream
java.io.IOException
- In case of an I/O problem
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