Class IOUtils
- java.lang.Object
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- org.apache.tomcat.util.http.fileupload.IOUtils
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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
BufferedInputStreamorBufferedReader. 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.
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Field Summary
Fields Modifier and Type Field Description static intEOFRepresents the end-of-file (or stream).
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Constructor Summary
Constructors Constructor Description IOUtils()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static voidcloseQuietly(Closeable closeable)Closes aCloseableunconditionally.static intcopy(InputStream input, OutputStream output)Copies bytes from anInputStreamto anOutputStream.static longcopyLarge(InputStream input, OutputStream output)Copies bytes from a large (over 2GB)InputStreamto anOutputStream.static intread(InputStream input, byte[] buffer, int offset, int length)Reads bytes from an input stream.static voidreadFully(InputStream input, byte[] buffer)Reads the requested number of bytes or fail if there are not enough left.static voidreadFully(InputStream input, byte[] buffer, int offset, int length)Reads the requested number of bytes or fail if there are not enough left.
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Field Detail
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EOF
public static final int EOF
Represents the end-of-file (or stream).- Since:
- 2.5 (made public)
- See Also:
- Constant Field Values
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Method Detail
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closeQuietly
public static void closeQuietly(Closeable closeable)
Closes aCloseableunconditionally.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
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copy
public static int copy(InputStream input, OutputStream output) throws IOException
Copies bytes from anInputStreamto anOutputStream.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
-1after the copy has completed since the correct number of bytes cannot be returned as an int. For large streams use thecopyLarge(InputStream, OutputStream)method.- Parameters:
input- theInputStreamto read fromoutput- theOutputStreamto write to- Returns:
- the number of bytes copied, or -1 if > Integer.MAX_VALUE
- Throws:
NullPointerException- if the input or output is nullIOException- if an I/O error occurs- Since:
- 1.1
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copyLarge
public static long copyLarge(InputStream input, OutputStream output) throws IOException
Copies bytes from a large (over 2GB)InputStreamto anOutputStream.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- theInputStreamto read fromoutput- theOutputStreamto write to- Returns:
- the number of bytes copied
- Throws:
NullPointerException- if the input or output is nullIOException- if an I/O error occurs- Since:
- 1.3
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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 ofInputStream.- Parameters:
input- where to read input frombuffer- destinationoffset- initial offset into bufferlength- 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:
- 2.2
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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 frombuffer- destinationoffset- initial offset into bufferlength- length to read, must be >= 0- Throws:
IOException- if there is a problem reading the fileIllegalArgumentException- if length is negativeEOFException- if the number of bytes read was incorrect- Since:
- 2.2
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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 frombuffer- destination- Throws:
IOException- if there is a problem reading the fileIllegalArgumentException- if length is negativeEOFException- if the number of bytes read was incorrect- Since:
- 2.2
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