Javase7 1641812
- 2. <Insert Picture Here> Java SE 7: New and Improved APIs
- 3. Agenda • New IO updates (NIO2 – JSR 203) • Concurrency updates (JSR-166y) • Collections updates • Client • Shaped/translucent windows • JLayer component • JDBC 4.1 • Java APIs for XML 3 3
- 4. New I/O 2 (NIO2) Libraries JSR 203 • Original Java I/O APIs presented challenges for developers • Not designed to be extensible • Many methods do not throw exceptions as expected • rename() method works inconsistently • Developers want greater access to file metadata • Java NIO2 solves these problems 4 4
- 5. Java NIO2 Features • Path is a replacement for File • Biggest impact on developers • Better directory support • list() method can stream via iterator • Entries can be filtered using regular expressions in API • Symbolic link support • java.nio.file.Filesystem • interface to a filesystem (FAT, ZFS, Zip archive, network, etc) • java.nio.file.attribute package • Access to file metadata 5 5
- 6. Path Class • Equivalent of java.io.File in the new API – Immutable • Methods to access and manipulate Path • Numerous ways to create a Path – From Paths and FileSystem //Make a reference to the path Path home = Paths.get(“/home/fred”); //Resolve tmp from /home/fred -> /home/fred/tmp Path tmpPath = home.resolve(“tmp”); //Create a relative path from tmp -> .. Path relativePath = tmpPath.relativize(home) File file = relativePath.toFile(); 6 6
- 7. File Operation – Create, Read, Write • Easy to open file for reading or writing Path file = Paths.get(“/home/fred/readme.txt”); InputStream is = Files.newInputStream(file); OutputStream os = Files.newOutputStream(file); • More advanced options for opening or creating files – Append to existing file, sparse file, delete on closing the file, etc. Path file = Paths.get(“/home/fred/readme.txt”); //Append to file Writer writer = Files.newBufferedWriter(file , StandardCharset.UTF_8 , StandardOpenOption.WRITE , StandardOpenOption.APPEND); 7 7
- 8. File Operation – Copy, Move • File copy is really easy – With fine grain control Path src = Paths.get(“/home/fred/readme.txt”); Path dst = Paths.get(“/home/fred/copy_readme.txt”); Files.copy(src, dst, StandardCopyOption.COPY_ATTRIBUTES, StandardCopyOption.REPLACE_EXISTING); • File move is supported – Optional atomic move supported Path src = Paths.get(“/home/fred/readme.txt”); Path dst = Paths.get(“/home/fred/readme.1st”); Files.move(src, dst, StandardCopyOption.ATOMIC_MOVE); 8 8
- 9. File Operation – Links • Hard and symbolic/soft links optionally supported • API based on long standing Unix semantics • Windows Vista or newer with NTFS • File operations on symbolic links are followed by default except • delete, move, walkFileTree • Creating hard link Path src = Paths.get(“/home/fred/readme.txt”); Path linkFile = Paths.get(“/home/fred/readme.lnk”); Files.createLink(linkFile, src); • Creating symbolic/soft link Files.createSymbolicLink(linkFile, src); 9 9
- 10. Directories • DirectoryStream iterate over entries – Scales to large directories – Uses less resources – Smooth out response time for remote file systems – Implements Iterable and Closeable for productivity • Filtering support – Build-in support for glob, regex and custom filters Path srcPath = Paths.get(“/home/fred/src”); try (DirectoryStream<Path> dir = srcPath.newDirectoryStream(“*.java”)) { for (Path file: dir) System.out.println(file.getName()); } 10 10
- 11. Recursive Operation • Interator to walk a file tree from a given starting point • FileVisitor invoked for each file/directory encountered – Based on visitor pattern • Depth first, invoked twice for each directory (pre/post) • Easy to develop recursive operations public interface FileVisitor<T> { FileVisitResult preVisitDirectory(T dir, BasicFileAttributes attrs); FileVisitResult visitFile(T file, BasicFileAttributes attrs); FileVisitResult visitFileFailed(T file, IOException ex); FileVisitResult postVisitDirectory(T dir, IOException ex); } 11 11
- 12. FileVisitor Example public class DeleteTildaFile extends SimpleFileVisitor<Path> { @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) { if (file.toFile().getName().endsWith(“~”)) Files.delete(file); return (FileVisitResult.CONTINUE); } } Path src = Paths.get(“/home/fred/src”); Files.walkFileTree(src, new DeleteTildaFile()); 12 12
- 13. File Attributes • Meta-data associated with file – File owner, permissions, timestamps, DOS attributes, extended attributes – Diverse and highly platform/file system specific • Approach: group related attributes – Providing typesafe and bulk access public interface PosixFileAttribute extends BasicFileAttribute { UserPrincipal owner(); GroupPrincipal group(); Set<PosixFilePermission> permissions(); } • Views to access these attributes – POSIX, ACL, DOS, extended, user defined, etc 13 13
- 14. File Attributes – Read, Set, Query • Reading file attributes PosixFileAttributeView view = Files.getFileAttributeView( file, PosixFileAttributeView.class); PosixFileAttributes attr = view.readAttributes(); System.out.println(“file owner = “ + attr.owner()); • Setting file attributes Set<PosixFilePermission> perms = PosixFilePermissions .fromString(“rw-r-----”); Files.setPosixFilePermissions(file, perms); • Querying supported attribute views Set<String> views = FileSystems.getDefault() .supportedFileAttributeViews(); 14 14
- 15. File Change Notifications • Watch files and directories for changes – Typically polled • WatchService – Watches registered objects for changes and events – Makes use of native event notification facility where possible – Monitors directories, generates events when files are created, deleted or modified – Extendable to other objects and events – Deliberately a low level interface 15 15
- 16. Major Classes • WatchService – Watches registered objects for changes and events – Allows multiple threads to poll/take events • Watchable – An object that is registered with WatchService – Implemented by Path • WatchKey – An object representing a registration • WatchEvent – An event 16 16
- 17. WatchService Example • Registering a WatchService WatchService watcher = FileSystems.getDefault().newWatchService(); Path tmp = Paths.get(“/home/fred/tmp”); tmp.register(watcher, StandardWatchEventKinds.ENTRY_CREATE , StandardWatchEventKinds.ENTRY_DELETE); • Retrieving and processing events while (true) { WatchKey key = watcher.take(); //non-blocking – poll() for (WatchEvent<?> event: key.pollEvents()) { if (StandardWatchEventKinds.ENTRY_CREATE == event.kind() { Path newFile = (Path)event.context(); ... } } key.reset(); } 17 17
- 18. FileSystem and FileStore • FileSystem is an interface to a file system – Also factory for files and other objects • Retrieving the default filesystem FileSystem fs = FileSystems.getDefault(); • Creating new file systems – eg. ZIP/JAR file system Map<String, String> attrs = new HashMap<>(); attrs.put(“create”, “true”); FileSystem zipfs = FileSystems.newFileSystems( “jar:file:/opt/tmp/myzip.zip”, attrs); • FileStore represents storage devices – Storage pools, partitions, volumes, etc • Provider interface to implement new file system type 18 18
- 19. Asynchronous I/O • java.io a short history – Pre JDK 1.4 – blocking I/O – JDK 1.4 onwards – non blocking I/O, memory mapped files, file lock, channels and buffers – JDK 7 – asynchronous I/O • Provides asynchronous I/O to both sockets and files – Take advantage of operating systems I/O facilities where available • Programming styles – Polling – I/O returns a Future object • Poll to test for I/O completion – Callback – specify a CompletionHandler when performing I/O • CompletionHandler invoked when I/O completes or fails 19 19
- 20. Asynchronous I/O – Example AsynchronousSocketChannel chan = AsynchronousSocketChannel.open(); //Non blocking connect/SOCK_NONBLOCK – polling Future<Void> result = chan.connect(new InetSocketAddress(...)); //Perform some operation until done result.isDone() result.get(); ByteBuffer buff = ByteBuffer.allocate(EIGHT_K); //Perform the read – callback chan.read(buff, buff, new MyCompletionHandler()); 20 20
- 21. Asynchronous I/O – Example pubilc class MyCompletionHandler implements CompletionHandler<Integer, ByteBuffer> { //Invoked when operation is completed public void completed(Integer result, ByteBuffer buff) { ... } //Invoked when operation fails public void failed(Throwable ex, ByteBuffer buff) { ... } } 21 21
- 22. Concurrency APIs • JSR166y • Update to JSR166x which was an update to JSR166 • Adds a lightweight task framework • Also referred to as Fork/Join • Phaser • Barrier similar to CyclicBarrier and CountDownLatch 22 22
- 23. Fork Join Framework • Goal is to take advantage of multiple processor • Designed for task that can be broken down into smaller pieces – Eg. Fibonacci number fib(10) = fib(9) + fib(8) • Typical algorithm that uses fork join if I can manage the task perform the task else fork task into x number of smaller/similar task join the results 23 23
- 24. Key Classes • ForkJoinPool – Executor service for running ForkJoinTask • ForkJoinTask – The base class for forkjoin task • RecursiveAction – A subclass of ForkJoinTask – A recursive resultless task – Implements compute() abstract method to perform calculation • RecursiveTask – Similar to RecursiveAction but returns a result 24 24
- 25. ForkJoin Example – Fibonacci public class Fibonacci extends RecursiveTask<Integer> { private final int number; public Fibonacci(int n) { number = n; } @Override protected Integer compute() { switch (number) { case 0: return (0); case 1: return (1); default: Fibonacci f1 = new Fibonacci(number – 1); Fibonacci f2 = new Fibonacci(number – 2); f1.fork(); f2.fork(); return (f1.join() + f2.join()); } } } 25 25
- 26. ForkJoin Example – Fibonacci ForkJoinPool pool = new ForkJoinPool(); Fibonacci r = new Fibonacci(10); pool.submit(r); while (!r.isDone()) { //Do some work ... } System.out.println("Result of fib(10) = “ + r.get()); 26 26
- 27. Collections Updates • TransferQueue interface • Extension to BlockingQueue • Implemented by LinkedTransferQueue • Producers may, or may not, wait for consumer to receive element • Can be capacity bounded or unbounded 27 27
- 28. Client Libraries • Nimbus Look and Feel • Platform APIs for shaped and translucent windows • JLayer (formerly from Swing labs) • Optimised 2D rendering 28 28
- 29. Shaped and Translucent Windows • Uniform translucency • Gradient translucency • Shaped 29 29
- 30. Shaped Window Example public class ShapedWindow extends JFrame { public ShapedWindow() { super("ShapedWindow"); addComponentListener(new ComponentAdapter() { @Override public void componentResized(ComponentEvent e) { setShape( new Ellipse2D.Double(0,0, getWidth(),getHeight())); } }); setUndecorated(true); } } 30 30
- 31. Nimbus Look and Feel • Better than Metal for cross platform look-and-feel • Introduced in Java SE 6u10, now part of Swing • Not the default L&F 31 31
- 32. JLayer and LayerUI • A decorator for Swing components – Layer on top of JPanel instead of using GlassPane – Paint on Swing components without subclassing the component – Can intercept AWT events • LayerUI performs the painting and event processing 32 32
- 33. LayerUI in Detail • Extend and typically override the following • paint(Graphics, JComponent) – draw on the component • installUI(JComponent) – configure the component eg. setting the event mask • processXXXEvent – process events (mouse, keyboard, etc) 33 33
- 34. JLayer Example public class MyDecorator extends LayerUI<JPanel> { @Override public void installUI(JComponent c) { super.installUI(c); JLayer l = (JLayer)c; l.setLayerEventMask(AWTEvent.KEY_EVENT_MASK); } @Override public void paint(Graphics g) { Graphics2D g2d = (Graphics2D)g; //Draw on g2d ... } } 34 34
- 35. JLayer Example //Create panel JPanel myPanel = ... MyDecorator myDecorator = new MyDecorator(); JLayer<JPanel> jLayer = new Jlayer<JPanel>(myPanel, myDecorator); 35 35
- 36. JDBC 4.1 Changes • Allow Connection, ResultSet and Statement objects to be used with the try-with-resources statement • Implement AutoCloseable interface • RowSetFactory and RowSetProvider classes added to javax.sql.rowset package 36 36
- 37. Java APIs for XML • JAXP 1.4.5 (Parsing) • Bug fixes, conformance, security, performance • StAX upgraded to version 1.2 • JAXB 2.2.3 (Binding) • Minor changes to XMLElement interface • JAX-WS 2.2.4 (Web Services) • Minor changes • Support for Async Servlet Transport using Servlet 3.0 API 37 37
- 38. java.util.Objects • Utility methods for operating on objects – Methods are null safe and null tolerant • Objects.deepEquals(Object a, Object b) – Deep equals • Objects.hashCode(Object o) – Return hash code of non-null argument or 0 for null argument • Objects.requireNonNull(T o) – Throws NullPointerException if o is null 38 38
- 39. Conclusions • Java SE 7 provides useful new APIs • File handling APIs make routine tasks much simpler • Fork-join framework simplifies concurrent decomposition of large tasks • Many other useful features • Java continues to deliver features developers require 39 39
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