nel fileChannel = AsynchronousFileChannel.open(path, StandardOpenOption.READ); ByteBuffer buffer = ByteBuffer.allocate(1024); long position = 0; Future operation = fileChannel.read(buffer CompletionHandlerByteBuffer>() { //Once the read operation finishes the CompletionHandler's completed() method will be calle . @Override public void completed(Integer result, ByteBuffer attachment) CompletionHandler will get called inst ad. @Override public void failed(Throwable exc, ByteBuffer attachment) { } }); 3. Writing Data ● Writing Data Via a Future Path path = Paths.get("data/test-write

java.nio.ByteBuffer, etc.) and is what all codecs work on. See Data Buffers and Codecs in the "Spring Core" section for more on this topic. The spring-core module provides byte[], ByteBuffer, DataBuffer and metadata values. By default only the basic codecs from spring-core for String, byte[], and ByteBuffer are registered. Adding spring-web provides access to more that can be registered as follows:

provided scope to avoid compile warnings. 435 Chapter 8. Data Buffers and Codecs Java NIO provides ByteBuffer but many libraries build their own byte buffer API on top, especially for network operations where implementations of DataBuffer can grow and shrink on demand. 2. Wrap an existing byte[] or java.nio.ByteBuffer, which decorates the given data with a DataBuffer implementation and that does not involve allocation y for others. 8.2. DataBuffer The DataBuffer interface offers similar operations as java.nio.ByteBuffer but also brings a few additional benefits some of which are inspired by the Netty ByteBuf. Below

and metadata values. By default only the basic codecs from spring-core for String, byte[], and ByteBuffer are registered. Adding spring-web provides access to more that can be registered as follows:

两个问题。 优化2 每天数百亿用户行为数据，美团点评怎么实现秒级转化分析？ - 美团技术团队 1. Unsafe调用。由于大部分的数据通过ByteBuffer访问，这里带来的额外开销对最终性能也有很大影响。Java lib中的 ByteBuffer访问接口是非常安全的，但安全也意味着低效，一次访问会有很多次的边界检查，而且多层函数的调用也 有很多额外开销。如果访问逻辑相对简单，对数据边界

源码缩略不进行展示：初始化一些需要的对象 val (rdd, func) = ser.deserialize[(RDD[T], (TaskContext, Iterator[T]) => U)]( ByteBuffer.wrap(taskBinary.value), Thread.currentThread. getContextClassLoader) _executorDeserializeTime