问

BufferOverflowException的原因是什么？

发布于 2023-02-08 09:19

异常堆栈是

java.nio.BufferOverflowException
     at java.nio.DirectByteBuffer.put(DirectByteBuffer.java:327)
     at java.nio.ByteBuffer.put(ByteBuffer.java:813)
            mappedByteBuffer.put(bytes);

代码:

randomAccessFile = new RandomAccessFile(file, "rw");
fileChannel = randomAccessFile.getChannel();
mappedByteBuffer = fileChannel.map(MapMode.READ_WRITE, 0, file.length());

并打电话 mappedByteBuffer.put(bytes);

是什么原因 mappedByteBuffer.put(bytes)抛出BufferOverflowException
如何查找原因？

1 个回答

FileChannel #map:

此方法返回的映射字节缓冲区的位置为零,限制和大小容量;

换句话说,如果bytes.length > file.length(),你应该收到一个BufferOverflowException.

为了证明这一点,我测试了这段代码:

File f = new File("test.txt");
try (RandomAccessFile raf = new RandomAccessFile(f, "rw")) {
  FileChannel ch = raf.getChannel();
  MappedByteBuffer buf = ch.map(MapMode.READ_WRITE, 0, f.length());
  final byte[] src = new byte[10];
  System.out.println(src.length > f.length());
  buf.put(src);
}

当且仅当 true打印时,抛出此异常:

Exception in thread "main" java.nio.BufferOverflowException
at java.nio.DirectByteBuffer.put(DirectByteBuffer.java:357)
at java.nio.ByteBuffer.put(ByteBuffer.java:832)

2023-02-08 09:24 回答

颂春堂中药

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