Question

有没有办法从java File对象中获取netty ByteBuf？我正在尝试使用Custom Snappy类来验证校验和。下面是我的代码，我想在File变量中获取bytebuf对象。

import io.netty.buffer.ByteBuf;

File file = new File("boot.zip");
ByteBuf byteBuf = Unpooled.buffer(128);
byteBuf.writeBytes(new FileInputStream(file));
int expectedChecksum = Snappy.calculateChecksum(byteBuf);
logger.info("checksum = "+expectedChecksum);

boolean checksumValid = true;
try {       
    CustomSnappy.validateChecksum(expectedChecksum, byteBuf);
} catch(DecompressionException e) {
    checksumValid = false;
    e.printStackTrace();
    logger.error("DecompressionException in checksum calculation " + e);            
} catch(Exception e) {
    checksumValid = false;
    e.printStackTrace();
    logger.error("Exception in checksum calculation " + e);
}

我使用了Unpooled.buffer（128），但它给了我No signature of method :io.netty.buffer.UnpooledHeapByteBuf.writeBytes() is applicable for argument types: (java.io.FileInputStream) values: [java.io.FileInputStream@28b6520b]

Answer 1

您可以从FileChannel创建MappedByteBuf并通过Unpooled.wrappedBuffer（..）将其包装在ByteBuffer中。

Answer 2

如果您使用的是JDK 1.7，java.nio.file.Files的类可以通过大量静态方法轻松实现。

ByteBuf buffer = Unpooled.copiedBuffer(Files.readAllBytes(new File(this.getClass().getResource("/requests/overPackageRequest").getFile()).toPath()));

Answer 3

以下是如何“从MappedByteBuf创建FileChannel并通过ByteBuffer将其包装在Unpooled.wrappedBuffer(..)中的示例”

    try {
        File file = new File(filename);
        FileInputStream fileInputStream = new FileInputStream(file);
        FileChannel fileChannel = fileInputStream.getChannel();
        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, file.length());

        ByteBuf byteBuf = Unpooled.wrappedBuffer(mappedByteBuffer);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 4

您可以使用方法ByteBuf#writeBytes(InputStream)。这应该有用，但我没有测试它。

ByteBuf buffer = // see http://stackoverflow.com/a/15088238/834
buffer.writeBytes(new FileInputStream(file), file.length());

请参阅http://netty.io/4.0/api/io/netty/buffer/ByteBuf.html#writeBytes(java.io.InputStream,%20int)

该文档显示了如何创建新的ByteBuf：http://netty.io/4.0/api/io/netty/buffer/Unpooled.html

如何将File对象转换为Netty ByteBuffer

4 个答案: