Package com.google.common.io

Class FileBackedOutputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable
    @Beta
@GwtIncompatible
@J2ObjCIncompatible
public final class FileBackedOutputStream
extends java.io.OutputStream
    An OutputStream that starts buffering to a byte array, but switches to file buffering once the data reaches a configurable size.

    When this stream creates a temporary file, it restricts the file's permissions to the current user or, in the case of Android, the current app. If that is not possible (as is the case under the very old Android Ice Cream Sandwich release), then this stream throws an exception instead of creating a file that would be more accessible. (This behavior is new in Guava 32.0.0. Previous versions would create a file that is more accessible, as discussed in Guava issue 2575. TODO: b/283778848 - Fill in CVE number once it's available.)

    Temporary files created by this stream may live in the local filesystem until either:

    • reset() is called (removing the data in this stream and deleting the file), or...
    • this stream (or, more precisely, its asByteSource() view) is finalized during garbage collection, AND this stream was not constructed with the 1-arg constructor or the 2-arg constructor passing false in the second parameter.

    This class is thread-safe.

    Since:
    1.0
    Author:
    Chris Nokleberg

    • Constructor Summary

      Constructors 
      Constructor Description
      FileBackedOutputStream​(int fileThreshold)
      Creates a new instance that uses the given file threshold, and does not reset the data when the ByteSource returned by asByteSource() is finalized.
      FileBackedOutputStream​(int fileThreshold, boolean resetOnFinalize)
      Creates a new instance that uses the given file threshold, and optionally resets the data when the ByteSource returned by asByteSource() is finalized.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      ByteSource asByteSource()
      Returns a readable ByteSource view of the data that has been written to this stream.
      void close()  
      void flush()  
      void reset()
      Calls close() if not already closed, and then resets this object back to its initial state, for reuse.
      void write​(byte[] b)  
      void write​(byte[] b, int off, int len)  
      void write​(int b)  

      • Methods inherited from class java.io.OutputStream

        nullOutputStream

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • FileBackedOutputStream

        public FileBackedOutputStream​(int fileThreshold)
        Creates a new instance that uses the given file threshold, and does not reset the data when the ByteSource returned by asByteSource() is finalized.
        Parameters:
        fileThreshold - the number of bytes before the stream should switch to buffering to a file
        Throws:
        java.lang.IllegalArgumentException - if fileThreshold is negative

      • FileBackedOutputStream

        public FileBackedOutputStream​(int fileThreshold,
                              boolean resetOnFinalize)
        Creates a new instance that uses the given file threshold, and optionally resets the data when the ByteSource returned by asByteSource() is finalized.
        Parameters:
        fileThreshold - the number of bytes before the stream should switch to buffering to a file
        resetOnFinalize - if true, the reset() method will be called when the ByteSource returned by asByteSource() is finalized.
        Throws:
        java.lang.IllegalArgumentException - if fileThreshold is negative

    • Method Detail

      • reset

        public void reset()
           throws java.io.IOException
        Calls close() if not already closed, and then resets this object back to its initial state, for reuse. If data was buffered to a file, it will be deleted.
        Throws:
        java.io.IOException - if an I/O error occurred while deleting the file buffer

      • write

        public void write​(int b)
           throws java.io.IOException
        Specified by:
        write in class java.io.OutputStream
        Throws:
        java.io.IOException

      • write

        public void write​(byte[] b)
           throws java.io.IOException
        Overrides:
        write in class java.io.OutputStream
        Throws:
        java.io.IOException

      • write

        public void write​(byte[] b,
                  int off,
                  int len)
           throws java.io.IOException
        Overrides:
        write in class java.io.OutputStream
        Throws:
        java.io.IOException

      • close

        public void close()
           throws java.io.IOException
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class java.io.OutputStream
        Throws:
        java.io.IOException

      • flush

        public void flush()
           throws java.io.IOException
        Specified by:
        flush in interface java.io.Flushable
        Overrides:
        flush in class java.io.OutputStream
        Throws:
        java.io.IOException