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[BAEL-15998] - Move articles out of core-java-io part 1

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This commit is contained in:
catalin-burcea
2019-11-06 17:04:00 +02:00
parent 0c8cad77ca
commit cd0b61cced
42 changed files with 111 additions and 281 deletions
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50
core-java-modules/core-java-nio-2/src/main/java/com/baeldung/selector/EchoClient.java Normal file
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package com.baeldung.selector;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
public class EchoClient {
private static SocketChannel client;
private static ByteBuffer buffer;
private static EchoClient instance;
public static EchoClient start() {
if (instance == null)
instance = new EchoClient();
return instance;
}
public static void stop() throws IOException {
client.close();
buffer = null;
}
private EchoClient() {
try {
client = SocketChannel.open(new InetSocketAddress("localhost", 5454));
buffer = ByteBuffer.allocate(256);
} catch (IOException e) {
e.printStackTrace();
}
}
public String sendMessage(String msg) {
buffer = ByteBuffer.wrap(msg.getBytes());
String response = null;
try {
client.write(buffer);
buffer.clear();
client.read(buffer);
response = new String(buffer.array()).trim();
System.out.println("response=" + response);
buffer.clear();
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}

75
core-java-modules/core-java-nio-2/src/main/java/com/baeldung/selector/EchoServer.java Normal file
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package com.baeldung.selector;
import java.io.File;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;
public class EchoServer {
private static final String POISON_PILL = "POISON_PILL";
public static void main(String[] args) throws IOException {
Selector selector = Selector.open();
ServerSocketChannel serverSocket = ServerSocketChannel.open();
serverSocket.bind(new InetSocketAddress("localhost", 5454));
serverSocket.configureBlocking(false);
serverSocket.register(selector, SelectionKey.OP_ACCEPT);
ByteBuffer buffer = ByteBuffer.allocate(256);
while (true) {
selector.select();
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> iter = selectedKeys.iterator();
while (iter.hasNext()) {
SelectionKey key = iter.next();
if (key.isAcceptable()) {
register(selector, serverSocket);
}
if (key.isReadable()) {
answerWithEcho(buffer, key);
}
iter.remove();
}
}
}
private static void answerWithEcho(ByteBuffer buffer, SelectionKey key) throws IOException {
SocketChannel client = (SocketChannel) key.channel();
client.read(buffer);
if (new String(buffer.array()).trim().equals(POISON_PILL)) {
client.close();
System.out.println("Not accepting client messages anymore");
}
buffer.flip();
client.write(buffer);
buffer.clear();
}
private static void register(Selector selector, ServerSocketChannel serverSocket) throws IOException {
SocketChannel client = serverSocket.accept();
client.configureBlocking(false);
client.register(selector, SelectionKey.OP_READ);
}
public static Process start() throws IOException, InterruptedException {
String javaHome = System.getProperty("java.home");
String javaBin = javaHome + File.separator + "bin" + File.separator + "java";
String classpath = System.getProperty("java.class.path");
String className = EchoServer.class.getCanonicalName();
ProcessBuilder builder = new ProcessBuilder(javaBin, "-cp", classpath, className);
return builder.start();
}
}

56
core-java-modules/core-java-nio-2/src/main/java/com/baeldung/symlink/SymLinkExample.java Normal file
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package com.baeldung.symlink;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.IntStream;
import static java.nio.file.StandardOpenOption.CREATE;
import static java.nio.file.StandardOpenOption.TRUNCATE_EXISTING;
public class SymLinkExample {
public void createSymbolicLink(Path link, Path target) throws IOException {
if (Files.exists(link)) {
Files.delete(link);
}
Files.createSymbolicLink(link, target);
}
public void createHardLink(Path link, Path target) throws IOException {
if (Files.exists(link)) {
Files.delete(link);
}
Files.createLink(link, target);
}
public Path createTextFile() throws IOException {
byte[] content = IntStream.range(0, 10000)
.mapToObj(i -> i + System.lineSeparator())
.reduce("", String::concat)
.getBytes(StandardCharsets.UTF_8);
Path filePath = Paths.get(".", "target_link.txt");
Files.write(filePath, content, CREATE, TRUNCATE_EXISTING);
return filePath;
}
public void printLinkFiles(Path path) throws IOException {
try (DirectoryStream<Path> stream = Files.newDirectoryStream(path)) {
for (Path file : stream) {
if (Files.isDirectory(file)) {
printLinkFiles(file);
} else if (Files.isSymbolicLink(file)) {
System.out.format("File link '%s' with target '%s'%n", file, Files.readSymbolicLink(file));
}
}
}
}
public static void main(String[] args) throws IOException {
new SymLinkExample().printLinkFiles(Paths.get("."));
}
}

23
core-java-modules/core-java-nio-2/src/main/java/com/baeldung/watcher/DirectoryWatcherExample.java Normal file
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package com.baeldung.watcher;
import java.io.IOException;
import java.nio.file.*;
public class DirectoryWatcherExample {
public static void main(String[] args) throws IOException, InterruptedException {
WatchService watchService = FileSystems.getDefault().newWatchService();
Path path = Paths.get(System.getProperty("user.home"));
path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_DELETE, StandardWatchEventKinds.ENTRY_MODIFY);
WatchKey key;
while ((key = watchService.take()) != null) {
for (WatchEvent<?> event : key.pollEvents()) {
System.out.println("Event kind:" + event.kind() + ". File affected: " + event.context() + ".");
}
key.reset();
}
watchService.close();
}
}

68
core-java-modules/core-java-nio-2/src/test/java/com/baeldung/mappedbytebuffer/MappedByteBufferUnitTest.java Normal file
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package com.baeldung.mappedbytebuffer;
import org.junit.Test;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.EnumSet;
import java.util.List;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
public class MappedByteBufferUnitTest {
@Test
public void givenFileChannel_whenReadToTheMappedByteBuffer_thenShouldSuccess() throws Exception {
// given
CharBuffer charBuffer = null;
Path pathToRead = getFileURIFromResources("fileToRead.txt");
// when
try (FileChannel fileChannel = (FileChannel) Files.newByteChannel(pathToRead, EnumSet.of(StandardOpenOption.READ))) {
MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size());
if (mappedByteBuffer != null) {
charBuffer = Charset.forName("UTF-8").decode(mappedByteBuffer);
}
}
// then
assertNotNull(charBuffer);
assertEquals(charBuffer.toString(), "This is a content of the file");
}
@Test
public void givenPath_whenWriteToItUsingMappedByteBuffer_thenShouldSuccessfullyWrite() throws Exception {
// given
final CharBuffer charBuffer = CharBuffer.wrap("This will be written to the file");
final Path pathToWrite = getFileURIFromResources("fileToWriteTo.txt");
// when
try (FileChannel fileChannel = (FileChannel) Files.newByteChannel(pathToWrite, EnumSet.of(StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING))) {
MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, charBuffer.length());
if (mappedByteBuffer != null) {
mappedByteBuffer.put(Charset.forName("utf-8").encode(charBuffer));
}
}
// then
final List<String> fileContent = Files.readAllLines(pathToWrite);
assertEquals(fileContent.get(0), "This will be written to the file");
}
//
private final Path getFileURIFromResources(String fileName) throws Exception {
final ClassLoader classLoader = getClass().getClassLoader();
return Paths.get(classLoader.getResource(fileName).toURI());
}
}

37
core-java-modules/core-java-nio-2/src/test/java/com/baeldung/selector/NioEchoLiveTest.java Normal file
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package com.baeldung.selector;
import com.baeldung.selector.EchoClient;
import com.baeldung.selector.EchoServer;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import static org.junit.Assert.assertEquals;
public class NioEchoLiveTest {
private Process server;
private EchoClient client;
@Before
public void setup() throws IOException, InterruptedException {
server = EchoServer.start();
client = EchoClient.start();
}
@Test
public void givenServerClient_whenServerEchosMessage_thenCorrect() {
String resp1 = client.sendMessage("hello");
String resp2 = client.sendMessage("world");
assertEquals("hello", resp1);
assertEquals("world", resp2);
}
@After
public void teardown() throws IOException {
server.destroy();
EchoClient.stop();
}
}

36
core-java-modules/core-java-nio-2/src/test/java/com/baeldung/symlink/SymLinkExampleManualTest.java Normal file
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package com.baeldung.symlink;
import org.junit.Test;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import static org.junit.Assert.*;
public class SymLinkExampleManualTest {
@Test
public void whenUsingFiles_thenCreateSymbolicLink() throws IOException {
SymLinkExample example = new SymLinkExample();
Path filePath = example.createTextFile();
Path linkPath = Paths.get(".", "symbolic_link.txt");
example.createSymbolicLink(linkPath, filePath);
assertTrue(Files.isSymbolicLink(linkPath));
}
@Test
public void whenUsingFiles_thenCreateHardLink() throws IOException {
SymLinkExample example = new SymLinkExample();
Path filePath = example.createTextFile();
Path linkPath = Paths.get(".", "hard_link.txt");
example.createHardLink(linkPath, filePath);
assertFalse(Files.isSymbolicLink(linkPath));
assertEquals(filePath.toFile()
.length(),
linkPath.toFile()
.length());
}
}

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core-java-modules/core-java-nio-2/src/test/resources/fileToRead.txt Normal file
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This is a content of the file

0
core-java-modules/core-java-nio-2/src/test/resources/fileToWriteTo.txt Normal file
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