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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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90
core-java-modules/core-java-io/src/main/java/com/baeldung/download/FileDownload.java
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package com.baeldung.download;
import org.apache.commons.io.FileUtils;
import org.asynchttpclient.*;
import java.io.*;
import java.net.*;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.util.concurrent.ExecutionException;
public class FileDownload {
public static void downloadWithJavaIO(String url, String localFilename) {
try (BufferedInputStream in = new BufferedInputStream(new URL(url).openStream()); FileOutputStream fileOutputStream = new FileOutputStream(localFilename)) {
byte dataBuffer[] = new byte[1024];
int bytesRead;
while ((bytesRead = in.read(dataBuffer, 0, 1024)) != -1) {
fileOutputStream.write(dataBuffer, 0, bytesRead);
}
} catch (IOException e) {
e.printStackTrace();
}
}
public static void downloadWithJava7IO(String url, String localFilename) {
try (InputStream in = new URL(url).openStream()) {
Files.copy(in, Paths.get(localFilename), StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
e.printStackTrace();
}
}
public static void downloadWithJavaNIO(String fileURL, String localFilename) throws IOException {
URL url = new URL(fileURL);
try (ReadableByteChannel readableByteChannel = Channels.newChannel(url.openStream());
FileOutputStream fileOutputStream = new FileOutputStream(localFilename); FileChannel fileChannel = fileOutputStream.getChannel()) {
fileChannel.transferFrom(readableByteChannel, 0, Long.MAX_VALUE);
fileOutputStream.close();
}
}
public static void downloadWithApacheCommons(String url, String localFilename) {
int CONNECT_TIMEOUT = 10000;
int READ_TIMEOUT = 10000;
try {
FileUtils.copyURLToFile(new URL(url), new File(localFilename), CONNECT_TIMEOUT, READ_TIMEOUT);
} catch (IOException e) {
e.printStackTrace();
}
}
public static void downloadWithAHC(String url, String localFilename) throws ExecutionException, InterruptedException, IOException {
FileOutputStream stream = new FileOutputStream(localFilename);
AsyncHttpClient client = Dsl.asyncHttpClient();
client.prepareGet(url)
.execute(new AsyncCompletionHandler<FileOutputStream>() {
@Override
public State onBodyPartReceived(HttpResponseBodyPart bodyPart) throws Exception {
stream.getChannel()
.write(bodyPart.getBodyByteBuffer());
return State.CONTINUE;
}
@Override
public FileOutputStream onCompleted(Response response) throws Exception {
return stream;
}
})
.get();
stream.getChannel().close();
client.close();
}
}

62
core-java-modules/core-java-io/src/main/java/com/baeldung/download/ResumableDownload.java
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package com.baeldung.download;
import java.io.*;
import java.net.*;
public class ResumableDownload {
public static long downloadFile(String downloadUrl, String saveAsFileName) throws IOException, URISyntaxException {
File outputFile = new File(saveAsFileName);
URLConnection downloadFileConnection = new URI(downloadUrl).toURL()
.openConnection();
return transferDataAndGetBytesDownloaded(downloadFileConnection, outputFile);
}
private static long transferDataAndGetBytesDownloaded(URLConnection downloadFileConnection, File outputFile) throws IOException {
long bytesDownloaded = 0;
try (InputStream is = downloadFileConnection.getInputStream(); OutputStream os = new FileOutputStream(outputFile, true)) {
byte[] buffer = new byte[1024];
int bytesCount;
while ((bytesCount = is.read(buffer)) > 0) {
os.write(buffer, 0, bytesCount);
bytesDownloaded += bytesCount;
}
}
return bytesDownloaded;
}
public static long downloadFileWithResume(String downloadUrl, String saveAsFileName) throws IOException, URISyntaxException {
File outputFile = new File(saveAsFileName);
URLConnection downloadFileConnection = addFileResumeFunctionality(downloadUrl, outputFile);
return transferDataAndGetBytesDownloaded(downloadFileConnection, outputFile);
}
private static URLConnection addFileResumeFunctionality(String downloadUrl, File outputFile) throws IOException, URISyntaxException, ProtocolException, ProtocolException {
long existingFileSize = 0L;
URLConnection downloadFileConnection = new URI(downloadUrl).toURL()
.openConnection();
if (outputFile.exists() && downloadFileConnection instanceof HttpURLConnection) {
HttpURLConnection httpFileConnection = (HttpURLConnection) downloadFileConnection;
HttpURLConnection tmpFileConn = (HttpURLConnection) new URI(downloadUrl).toURL()
.openConnection();
tmpFileConn.setRequestMethod("HEAD");
long fileLength = tmpFileConn.getContentLengthLong();
existingFileSize = outputFile.length();
if (existingFileSize < fileLength) {
httpFileConnection.setRequestProperty("Range", "bytes=" + existingFileSize + "-" + fileLength);
} else {
throw new IOException("File Download already completed.");
}
}
return downloadFileConnection;
}
}

50
core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio/selector/EchoClient.java
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package com.baeldung.java.nio.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-io/src/main/java/com/baeldung/java/nio/selector/EchoServer.java
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package com.baeldung.java.nio.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();
}
}

2
core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio/selector/README.md
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@@ -1,2 +0,0 @@
###Relevant Articles:
- [Introduction to the Java NIO Selector](http://www.baeldung.com/java-nio-selector)

56
core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio2/visitor/FileSearchExample.java
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@@ -1,56 +0,0 @@
package com.baeldung.java.nio2.visitor;
import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import static java.nio.file.FileVisitResult.CONTINUE;
import static java.nio.file.FileVisitResult.TERMINATE;
public class FileSearchExample implements FileVisitor<Path> {
private final String fileName;
private final Path startDir;
public FileSearchExample(String fileName, Path startingDir) {
this.fileName = fileName;
startDir = startingDir;
}
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
return CONTINUE;
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
String fileName = file.getFileName().toString();
if (this.fileName.equals(fileName)) {
System.out.println("File found: " + file.toString());
return TERMINATE;
}
return CONTINUE;
}
@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
System.out.println("Failed to access file: " + file.toString());
return CONTINUE;
}
@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
boolean finishedSearch = Files.isSameFile(dir, startDir);
if (finishedSearch) {
System.out.println("File:" + fileName + " not found");
return TERMINATE;
}
return CONTINUE;
}
public static void main(String[] args) throws IOException {
Path startingDir = Paths.get("C:/Users/new/Desktop");
FileSearchExample crawler = new FileSearchExample("hibernate.txt", startingDir);
Files.walkFileTree(startingDir, crawler);
}
}

30
core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio2/visitor/FileVisitorImpl.java
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package com.baeldung.java.nio2.visitor;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
public class FileVisitorImpl implements FileVisitor<Path> {
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
return null;
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
return null;
}
@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) {
return null;
}
@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
return null;
}
}

29
core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio2/watcher/DirectoryWatcherExample.java
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@@ -1,29 +0,0 @@
package com.baeldung.java.nio2.watcher;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
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();
}
}

54
core-java-modules/core-java-io/src/main/java/com/baeldung/symlink/SymLinkExample.java
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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 static java.nio.file.StandardOpenOption.*;
import java.util.stream.IntStream;
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("."));
}
}