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Downloader.java
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Downloader.java
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import java.io.IOException;
import java.net.*;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.StandardCharsets;
import java.util.*;
public class Downloader {
static public class NioHTTPClient {
public interface HTTPResponseListener {
void onResponse(int statusCode, String statusText, Map<String, String> headers) throws IOException;
void onData(byte[] buffer) throws IOException;
}
public static final String CRLF = "\r\n";
private Selector selector;
private SocketChannel socketChannel;
public HTTPResponseListener listener;
private String request;
private ByteBuffer buffer;
private boolean isResponseParsed = false;
public NioHTTPClient(Selector selector) {
this.selector = selector;
}
public void cancel() throws IOException {
socketChannel.keyFor(selector).cancel();
selector.selectNow();
this.socketChannel.close();
}
public void sendRequest(String method, String url, ArrayList<String> headers) throws IOException {
this.socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
URL u = URI.create(url).toURL();
int port = u.getPort() == -1 ? u.getDefaultPort() : u.getPort();
socketChannel.connect(new InetSocketAddress(u.getHost(), port));
String path = u.getPath().isBlank() ? "/" : u.getPath();
path += u.getQuery() == null ? "" : "?" + u.getQuery();
request = method + " " + path + " HTTP/1.1" + CRLF;
request += "Host: " + u.getHost() + CRLF + "User-Agent: NioHTTPDownload/1.0" + CRLF;
for (String header : headers) {
request += header + CRLF;
}
request += CRLF;
socketChannel.register(this.selector, SelectionKey.OP_CONNECT).attach(this);
}
public void onConnect(SelectionKey key) throws IOException {
if (socketChannel.finishConnect()) {
buffer = ByteBuffer.allocate(8192);
key.interestOps(SelectionKey.OP_WRITE);
}
}
public void onCanWrite(SelectionKey key) throws IOException {
if (request != null) {
socketChannel.write(ByteBuffer.wrap(request.getBytes(StandardCharsets.UTF_8)));
key.interestOps(SelectionKey.OP_READ);
request = null;
}
}
public void onCanRead(SelectionKey key) throws IOException {
if (socketChannel.read(buffer) == -1) {
cancel();
return;
}
buffer.flip();
if (!isResponseParsed) {
int start = 0;
while (start < buffer.limit() - 3) {
if (buffer.get(start) == '\r' && buffer.get(start + 1) == '\n' && buffer.get(start + 2) == '\r'
&& buffer.get(start + 3) == '\n') {
start += 4;
break;
}
start++;
}
if (start == buffer.limit() - 3) {
return;
}
byte[] response = new byte[start];
buffer.get(response);
String[] lines = new String(response, StandardCharsets.UTF_8).split(CRLF);
if (lines.length < 1) {
cancel();
return;
}
String[] statusLine = lines[0].split(" ");
Map<String, String> headers = new java.util.HashMap<>();
for (int i = 1; i < lines.length; i++) {
String[] pair = lines[i].split(":");
headers.put(pair[0].trim().toLowerCase(), pair[1].trim());
}
listener.onResponse(Integer.parseInt(statusLine[1]), statusLine[2], headers);
isResponseParsed = true;
}
if (buffer.hasRemaining()) {
byte remaining[] = new byte[buffer.remaining()];
buffer.get(remaining);
listener.onData(remaining);
buffer.clear();
}
}
}
public static void main(String[] args) throws IOException {
String url = "http://ruzhila.cn/favicon.ico";
String output = "favicon.ico";
if (args.length > 0) {
url = args[0];
}
if (args.length > 1) {
output = args[1];
}
final String outputFinal = output;
Selector selector = Selector.open();
NioHTTPClient downloadRequest = new NioHTTPClient(selector);
downloadRequest.listener = new NioHTTPClient.HTTPResponseListener() {
private int remaining = -1;
private int contentLength = -1;
private java.io.FileOutputStream fileOutputStream;
@Override
public void onResponse(int statusCode, String statusText,
Map<String, String> headers) throws IOException {
if (headers.containsKey("content-length")) {
remaining = Integer.parseInt(headers.get("content-length"));
contentLength = remaining;
}
System.out.println("Downloading..." + contentLength);
fileOutputStream = new java.io.FileOutputStream(outputFinal);
}
@Override
public void onData(byte[] buffer) throws IOException {
remaining -= buffer.length;
System.out.println("Remaining: " + remaining + "/" + contentLength + " bytes");
fileOutputStream.write(buffer);
if (remaining <= 0) {
System.out.println("Download completed");
downloadRequest.cancel();
}
}
};
downloadRequest.sendRequest("GET", url, new ArrayList<>());
while (selector.keys().size() > 0) {
selector.select();
for (SelectionKey key : selector.selectedKeys()) {
NioHTTPClient client = (NioHTTPClient) key.attachment();
if (key.isConnectable()) {
client.onConnect(key);
} else if (key.isWritable()) {
client.onCanWrite(key);
} else if (key.isReadable()) {
client.onCanRead(key);
}
}
selector.selectedKeys().clear();
}
}
}