Java NIO分散读聚集写

野性酷女 2022-04-03 06:07 234阅读 0赞

\#Java NIO分散读 聚集写

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> Java NIO 开始支持scatter/gather（分散读/聚集写），scatter/gather用于描述从channel中读取或者写入到channel的操作。

### 1. 概念 ###

> 分散（scatter）从channel中读取是指在读操作的时候将读取的数据写入到多个buffer中，因此，channel将读取到的数据分散到多个buffer中。当一个buffer被写满之后，才会进行下一个buffer的写入。

![图片描述][tapd_personalword_1134171118001000141_base64_1545303051_58.png]

> 聚集（scatter）是指将多个 Buffer 中的数据“聚集”到 Channel。一个buffer读完之后，才会进行下一个buffer的读入

![图片描述][tapd_personalword_1134171118001000141_base64_1545303061_100.png]

### 2. 代码 ###

public class ScatterReadAndGatheringWrite {
        public static void main(String[] args) {
            String src1 = "src/file.txt";
            String src2 = "src/file.copy.txt";
            ByteBuffer byteBuffer1 = ByteBuffer.allocate(1);
            ByteBuffer byteBuffer2 = ByteBuffer.allocate(100);
            byteBuffer1.clear();
            byteBuffer2.clear();
            ByteBuffer[] bufs={byteBuffer1, byteBuffer2};
    
            FileInputStream fileInputStream = null;
            FileOutputStream fileOutputStream = null;
            try {
                fileInputStream = new FileInputStream(src1);
                FileChannel inChannel = fileInputStream.getChannel();
    
                fileOutputStream = new FileOutputStream(src2);
                FileChannel outChannel = fileOutputStream.getChannel();
    
                while (true) {
    
                    //开始写数据到buffer中
                    long r = inChannel.read(bufs);
                    System.out.println(r);
                    if (r == 0) {
                        break;
                    }
    
                    //切换到读模式
                    for (ByteBuffer buffer : bufs) {
                        buffer.flip();
                    }
    
                    //System.out.println("buffer.position=" + byteBuffer1.position());
                    //System.out.println("buffer.capacity=" + byteBuffer1.capacity());
                    //System.out.println("buffer.limit=" + byteBuffer1.limit());
                    outChannel.write(bufs);
    
                }
    
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    }

### 3. 参考文章 ###

[https://blog.csdn.net/qq\_33804730/article/details/79171188][https_blog.csdn.net_qq_33804730_article_details_79171188]  
[https://blog.csdn.net/jkxqj/article/details/77480006][https_blog.csdn.net_jkxqj_article_details_77480006]

[tapd_personalword_1134171118001000141_base64_1545303051_58.png]: https://www.tapd.cn/tfl/captures/2018-12/tapd_personalword_1134171118001000141_base64_1545303051_58.png
[tapd_personalword_1134171118001000141_base64_1545303061_100.png]: https://www.tapd.cn/tfl/captures/2018-12/tapd_personalword_1134171118001000141_base64_1545303061_100.png
[https_blog.csdn.net_qq_33804730_article_details_79171188]: https://blog.csdn.net/qq_33804730/article/details/79171188
[https_blog.csdn.net_jkxqj_article_details_77480006]: https://blog.csdn.net/jkxqj/article/details/77480006