Guiqiang Zhang

I have write a new NIO server thread, which accept messages from client, but there is some problem. which make it loop too much quickly which make cpu usage to 100%, my run method is follow, any problem?

public void run() {
try {
// This map is used to store clientChannel - Connection pair set,
// store it while accepting a client socket, and retrieve it while reading client request.
final Map channelToConnection = new HashMap();

while (!shouldStop) {
// waiting for events with timeout value
if (selector.select() == 0) {
continue;
}

Iterator it = selector.selectedKeys().iterator();
// process every selectionKey
while (it.hasNext()) {
SelectionKey key = (SelectionKey) it.next();

// a client required a connection
if (key.isAcceptable()) {
synchronized (this) {
// reach the max connections limit
if ((this.maxConnections > 0)
&& (this.connectionIdToChannel.size() >= this.maxConnections)) {
continue;
}
}

it.remove();

// get client socket channel
SocketChannel client = server.accept();

// Set Non-Blocking mode for select operation
client.configureBlocking(false);

// recording to the selector (reading)
client.register(selector, SelectionKey.OP_READ);

Connection connection =
new Connection(generator.getNextUUID().toString(), this, client.socket());

synchronized (this) {
connectionIdToChannel.put(connection.getId(), client);
}

channelToConnection.put(client, connection);

// Notify all handlers to process this connection
for (Iterator connIter = this.handlers.values().iterator(); connIter.hasNext() {
((Handler) connIter.next()).onConnect(connection);
}
} else if (key.isReadable()) {
// if isReadable = true then the server is ready to read
it.remove();

final SocketChannel client = (SocketChannel) key.channel();

try {
Message request = null;
while ((request = IOHelper.readMessage(client, messageFactory)) != null) {
Handler handler = getHandler(request.getHandlerId());

// If no handler register for the given request, simply ignore the request.
if (handler != null) {
// Handler exists for the request.
handler.handleRequest((Connection) channelToConnection.get(client), request);
}
}
} catch (IOException e) {
this.setLastException(e);
// Failed to read from client, so close the corresponding connection
Connection con = (Connection) channelToConnection.remove(client);
this.closeConnection(con.getId());
}
}
}
}
} catch (ProcessingException e) {
this.setLastException(e);
} catch (IOException e) {
this.setLastException(e);
} finally {
synchronized (this) {
this.started = false;
this.shouldStop = false;

// close everything
try {
this.selector.close();
} catch (IOException e) {
e.printStackTrace();
}

try {
this.server.close();
} catch (IOException e) {
e.printStackTrace();
}

this.selector = null;
this.server = null;
this.connectionIdToChannel.clear();
}
}
}

great! that is good. thanks.

I have already tryed this way, but it says The final field XXX may already have been assigned.

for example. I have define a class A, that A's constuctor throws Exception E, and I class B there is a field private static final a;
how to initialize it is a better way?

May you can use javascript.

I think:
both will be used when in any proper time.
if the validation can be done in the client side and there is no critical data you don't want user to see, like form field format validation
... you can use client validation,but when the validation refer to some important data ,you should do validation in the server side.
This is my personal opinion!@