7. NIO Features Channel and Buffers File locking Memory Mapped Files Scatter and Gather Channel to Channel Transfer Non-Blocking Sockets Multiplexed I/O
10. Buffer Basic Operations: Creating Filling and Draining Flipping and Rewind Marking Comparing Duplicating
11. Creating public static XXXBuffer allocate (int capacity) public static XXXBuffer wrap (XXX [] array) public static XXXBuffer wrap (XXX [] array, int offset,int length) For e.g. CharBuffer charBuffer= CharBuffer.allocate(10); char [] charArray = new char [10]; CharBuffercharbuffer = CharBuffer.wrap (charArray ); CharBuffercharbuffer = CharBuffer.wrap (charArray, 2, 7);
12. Filling and Draining XXXBuffer put (XXX b); XXXBuffer put (int index, XXX b); XXX get( ); XXX get(int index); XXXBufferput (XXX[] src); XXXBuffer put(XXX [] src, int offset, int length); XXXBuffer get(XXX[] dest); XXXBuffer get(XXX [] dest, int offset, int length);
13. Flipping and Rewind Manually Flipping a Buffer: buffer.limit(buffer.position( )).position(0) API provides Flip and rewind method: Buffer flip() Buffer rewind()
14. Marking Buffer mark() Buffer reset() For e.g buffer.position(2).mark( ).position(4);
41. Readiness Selection Socket channels can be check for readiness A single thread can monitor a large number of socket Steps to do readiness selection Create a Selector instance Register one or more non-blocking channels with it Implement a infinite loop and wait for events Get the selected keys list and iterate the keys Process the events. Remove the key from the list
49. SeekableByteChannel A byte channel that maintains a current position and allows the position to be changed. Key Methods SeekableByteChannel position(long newPosition) SeekableByteChannel truncate(long size)
50. NetworkChannel & MulticastChanneljava.nio.channels NetworkChannels: All the network-oriented channels implements the new NetworkChannel interface We can easily bind the channel socket, set and query for socket options MulticastChannels: We can send and receive IP datagrams from a complete group Implement by DatagramChannel and AsynchronousDatagramChannel
51. Pathjava.nio.file Locates a file using a system dependent path Defines methods to access and manipulate paths Defines methods to access files
52. Creating a Path // Microsoft Windows Path p1 = Paths.get("C:homejoefoo"); // Solaris syntax Path path = Paths.get("/home/joe/foo"); Path p4 = FileSystems.getDefault().getPath("/users/sally");
58. Walk File Tree Walk a file tree rooted at a given starting file Implement FileVisitor interface Initiate the process by calling anyone of the below method of java.nio.file.FilesClass walkFileTree(Path start, FileVisitor<? super Path> visitor) walkFileTree(Path start, Set<FileVisitOption> options, intmaxDepth, FileVisitor<? super Path> visitor)
61. File Change Notification Looking for file changes in FileSystem Using the native event facility whenever available Steps required to implement a watch service Create a WatchService "watcher" for the file system. For each directory that you want monitored, register it with the watcher. Implement an infinite loop to wait for incoming events Retrieve the key from the watcher's queue. Process all the events associated with the Key. Reset the key, and resume waiting for events. Close the service
64. WatchKeyjava.nio.file WatchKey represents registration of a watchable object with a WatchService. Key Methods: List<WatchEvent<?>> pollEvents() Watchable watchable() boolean reset() boolean isValid() void cancel()
65. File Attributesjava.nio.file.attribute Meta-data associated with file Generalized metadata API Fetch a file's attributes in one bulk operation Map<String,Object> readAttributes(Path, String, LinkOption...) <A extends BasicFileAttributes> readAttributes(Path, Class<A>, LinkOption...) Grouping of related attributes and Views to access the attribute groups.
68. Asynchronous I/Ojava.nio.channels They provide asynchronous operations for both sockets and files. All operations work in non-blocking mode. All the asynchronous I/O operations have one of two forms : The first one returns a java.util.concurrent.Future that represent the pending result The second one is created using a CompletionHandler.
70. CompletionHandler Future result = channel.read(buffer, 100, buffer, new CompletionHandler(){ public void completed(Integer result, ByteBuffer buffer){ //Compute the result } public void failed(Throwable exception, ByteBuffer buffer){ // Handle the error } });
71. References: Java NIO by Ron Hitchens Publisher: O’Reilly http://java.sun.com/developer/technicalArticles/javase/nio/ http://download.oracle.com/javase/tutorial/essential/io/index.html