java.nio Selectors和SocketChannel用於繼續流式傳輸
[英]java.nio Selectors and SocketChannel for continues Streaming
問題描述
我目前正在為一個應用程序使用java.nio.channel.Selectors和SocketChannels，該應用程序將打開1對多連接以繼續流式傳輸到服務器。 我的應用程序有三個線程：StreamWriteWorker - 對SocketChannel執行寫操作，StreamReadWorker - 從緩沖區讀取字節並解析內容，StreamTaskDispatcher - 執行Selector對readyOps的選擇，並為工作線程調度新的runnable。
問題 - 選擇器的選擇方法上的調用僅在第一次調用時返回值> 0（有效的readyOps）; 我能夠在所有就緒通道上執行一次寫入和發送數據，但是Selector選擇方法的以下所有調用都返回0。
問題：每次讀/寫后我是否需要在SocketChannel上調用close（我希望不是！）？ 如果不是什么原因可能導致SocketChannel無法用於任何讀/寫操作？
對不起，我不能發布代碼，但我希望我已經清楚地解釋了這個問題，以便有人幫忙。 我已經搜索了答案，我看到你關閉后不能重用SocketChannel連接，但我的頻道不應該關閉，服務器永遠不會收到EOF流結果。
我取得了一些進展，並發現由於json解析錯誤，服務器應用程序上沒有發生寫操作。 所以現在我的客戶端應用程序代碼上的SocketChannel在處理讀取操作后就可以進行另一次寫操作了。 我想這是SocketChannels的TCP特性。 但是，SocketChannel不可用於服務器應用程序端的另一個讀取操作。 這是SocketChannels的正常行為嗎？ 在讀取操作之后是否需要在客戶端關閉連接並建立新連接？
這是我想要做的代碼示例：
package org.stream.socket;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CodingErrorAction;
import java.util.HashMap;
import java.util.Iterator;
import java.util.UUID;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.commons.lang3.RandomStringUtils;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonPrimitive;
import com.google.gson.stream.JsonToken;
public class ClientServerTest {
private LinkedBlockingQueue<byte[]> dataQueue = new LinkedBlockingQueue<byte[]>();
private ExecutorService executor = Executors.newFixedThreadPool(1);
private HashMap<String, Integer> uuidToSize = new HashMap<String, Integer>();
private class StreamWriteTask implements Runnable {
private ByteBuffer buffer;
private SelectionKey key;
private Selector selector;
private StreamWriteTask(ByteBuffer buffer, SelectionKey key, Selector selector) {
this.buffer = buffer;
this.key = key;
this.selector = selector;
}
@Override
public void run() {
SocketChannel sc = (SocketChannel) key.channel();
byte[] data = (byte[]) key.attachment();
buffer.clear();
buffer.put(data);
buffer.flip();
int results = 0;
while (buffer.hasRemaining()) {
try {
results = sc.write(buffer);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (results == 0) {
buffer.compact();
buffer.flip();
data = new byte[buffer.remaining()];
buffer.get(data);
key.interestOps(SelectionKey.OP_WRITE);
key.attach(data);
selector.wakeup();
return;
}
}
key.interestOps(SelectionKey.OP_READ);
key.attach(null);
selector.wakeup();
}
}
private class StreamReadTask implements Runnable {
private ByteBuffer buffer;
private SelectionKey key;
private Selector selector;
private StreamReadTask(ByteBuffer buffer, SelectionKey key, Selector selector) {
this.buffer = buffer;
this.key = key;
this.selector = selector;
}
private boolean checkUUID(byte[] data) {
return uuidToSize.containsKey(new String(data));
}
@Override
public void run() {
SocketChannel sc = (SocketChannel) key.channel();
buffer.clear();
byte[] data = (byte[]) key.attachment();
if (data != null) {
buffer.put(data);
}
int count = 0;
int readAttempts = 0;
try {
while ((count = sc.read(buffer)) > 0) {
readAttempts++;
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (count == 0) {
buffer.flip();
data = new byte[buffer.limit()];
buffer.get(data);
if (checkUUID(data)) {
key.interestOps(SelectionKey.OP_READ);
key.attach(data);
} else {
System.out.println("Clinet Read - uuid ~~~~ " + new String(data));
key.interestOps(SelectionKey.OP_WRITE);
key.attach(null);
}
}
if (count == -1) {
try {
sc.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
selector.wakeup();
}
}
private class ClientWorker implements Runnable {
@Override
public void run() {
try {
Selector selector = Selector.open();
SocketChannel sc = SocketChannel.open();
sc.configureBlocking(false);
sc.connect(new InetSocketAddress("127.0.0.1", 9001));
sc.register(selector, SelectionKey.OP_CONNECT);
ByteBuffer buffer = ByteBuffer.allocateDirect(65535);
while (selector.isOpen()) {
int count = selector.select(10);
if (count == 0) {
continue;
}
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while (it.hasNext()) {
final SelectionKey key = it.next();
it.remove();
if (!key.isValid()) {
continue;
}
if (key.isConnectable()) {
sc = (SocketChannel) key.channel();
if (!sc.finishConnect()) {
continue;
}
sc.register(selector, SelectionKey.OP_WRITE);
}
if (key.isReadable()) {
key.interestOps(0);
executor.execute(new StreamReadTask(buffer, key, selector));
}
if (key.isWritable()) {
key.interestOps(0);
if(key.attachment() == null){
key.attach(dataQueue.take());
}
executor.execute(new StreamWriteTask(buffer, key, selector));
}
}
}
} catch (IOException ex) {
// Handle Exception
}catch(InterruptedException ex){
}
}
}
private class ServerWorker implements Runnable {
@Override
public void run() {
try {
Selector selector = Selector.open();
ServerSocketChannel ssc = ServerSocketChannel.open();
ServerSocket socket = ssc.socket();
socket.bind(new InetSocketAddress(9001));
ssc.configureBlocking(false);
ssc.register(selector, SelectionKey.OP_ACCEPT);
ByteBuffer buffer = ByteBuffer.allocateDirect(65535);
DataHandler handler = new DataHandler();
while (selector.isOpen()) {
int count = selector.select(10);
if (count == 0) {
continue;
}
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while (it.hasNext()) {
final SelectionKey key = it.next();
it.remove();
if (!key.isValid()) {
continue;
}
if (key.isAcceptable()) {
ssc = (ServerSocketChannel) key.channel();
SocketChannel sc = ssc.accept();
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
}
if (key.isReadable()) {
handler.readSocket(buffer, key);
}
if (key.isWritable()) {
handler.writeToSocket(buffer, key);
}
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
private class DataHandler {
private JsonObject parseData(StringBuilder builder) {
if (!builder.toString().endsWith("}")) {
return null;
}
JsonParser parser = new JsonParser();
JsonObject obj = (JsonObject) parser.parse(builder.toString());
return obj;
}
private void readSocket(ByteBuffer buffer, SelectionKey key)
throws IOException {
SocketChannel sc = (SocketChannel) key.channel();
buffer.clear();
int count = Integer.MAX_VALUE;
int readAttempts = 0;
try {
while ((count = sc.read(buffer)) > 0) {
readAttempts++;
}
} catch (IOException e) {
e.printStackTrace();
}
if (count == 0) {
buffer.flip();
StringBuilder builder = key.attachment() instanceof StringBuilder ? (StringBuilder) key
.attachment() : new StringBuilder();
Charset charset = Charset.forName("UTF-8");
CharsetDecoder decoder = charset.newDecoder();
decoder.onMalformedInput(CodingErrorAction.IGNORE);
System.out.println(buffer);
CharBuffer charBuffer = decoder.decode(buffer);
String content = charBuffer.toString();
charBuffer = null;
builder.append(content);
System.out.println(content);
JsonObject obj = parseData(builder);
if (obj == null) {
key.attach(builder);
key.interestOps(SelectionKey.OP_READ);
} else {
System.out.println("data ~~~~~~~ " + builder.toString());
JsonPrimitive uuid = obj.get("uuid").getAsJsonPrimitive();
key.attach(uuid.toString().getBytes());
key.interestOps(SelectionKey.OP_WRITE);
}
}
if (count == -1) {
key.attach(null);
sc.close();
}
}
private void writeToSocket(ByteBuffer buffer, SelectionKey key)
throws IOException {
SocketChannel sc = (SocketChannel) key.channel();
byte[] data = (byte[]) key.attachment();
buffer.clear();
buffer.put(data);
buffer.flip();
int writeAttempts = 0;
while (buffer.hasRemaining()) {
int results = sc.write(buffer);
writeAttempts++;
System.out.println("Write Attempt #" + writeAttempts);
if (results == 0) {
buffer.compact();
buffer.flip();
data = new byte[buffer.remaining()];
buffer.get(data);
key.attach(data);
key.interestOps(SelectionKey.OP_WRITE);
break;
}
}
key.interestOps(SelectionKey.OP_READ);
key.attach(null);
}
}
public ClientServerTest() {
for (int index = 0; index < 1000; index++) {
JsonObject obj = new JsonObject();
String uuid = UUID.randomUUID().toString();
uuidToSize.put(uuid, uuid.length());
obj.addProperty("uuid", uuid);
String data = RandomStringUtils.randomAlphanumeric(10000);
obj.addProperty("event", data);
dataQueue.add(obj.toString().getBytes());
}
Thread serverWorker = new Thread(new ServerWorker());
serverWorker.start();
Thread clientWorker = new Thread(new ClientWorker());
clientWorker.start();
}
/**
* @param args
*/
public static void main(String[] args) {
ClientServerTest test = new ClientServerTest();
for(;;){
}
}
}
1 個解決方案
解決方案1
4 已采納 2012-05-25 07:56:11
處理
OP_CONNECT的正確方法是嘗試一次finishConnect()，如果成功取消注冊OP_CONNECT並注冊OP_READ或OP_WRITE，則可能是后者，因為您是客戶端。 在非阻塞模式下循環和睡眠是沒有意義的。 如果finishConnect()返回false，則OP_CONNECT將再次觸發。你對
!key.isAcceptable()!key.isReadable()和!key.isWriteable()絕對沒有任何意義。 如果密鑰可以接受，請調用accept()。 如果它是可讀的，請調用read()。 如果它是可寫的，請調用write()。 就這么簡單。您需要注意，通道幾乎總是可寫的，除了它們的套接字發送緩沖區已滿的短暫時期。 所以只有在你有東西要寫的時候才能注冊
OP_WRITE，或者在你嘗試寫入並獲得零回報后更好。 然后當OP_WRITE觸發時，重試寫入並取消注冊OP_WRITE除非你得到另一個零。你的
ByteBuffer太經濟了。 實際上， 每個頻道需要一個。 您可以將其保存為密鑰附件，以便在需要時將其恢復。 否則，您沒有任何方法可以累積部分讀取，這些讀取肯定會發生，或者任何重試寫入的方式。
這些語句是否相等？（java.nio）
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