mina2 请求过滤器实现

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package org.apache.mina.filter.firewall;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.mina.core.filterchain.IoFilter;
import org.apache.mina.core.filterchain.IoFilterAdapter;
import org.apache.mina.core.session.IoSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A {@link IoFilter} which blocks connections from connecting
* at a rate faster than the specified interval.
*
* @author <a href="http://mina.apache.org">Apache MINA Project</a>
*/
public class ConnectionThrottleFilter extends IoFilterAdapter {
/** A logger for this class */
private final static Logger LOGGER = LoggerFactory.getLogger(ConnectionThrottleFilter.class);
/** The default delay to wait for a session to be accepted again */
private static final long DEFAULT_TIME = 1000;
/**
* The minimal delay the sessions will have to wait before being created
* again
*/
private long allowedInterval;
/** The map of created sessiosn, associated with the time they were created */
private final Map<String, Long> clients;
/** A lock used to protect the map from concurrent modifications */
private Lock lock = new ReentrantLock();
// A thread that is used to remove sessions that have expired since they
// have
// been added.
private class ExpiredSessionThread extends Thread {
public void run() {
try {
// Wait for the delay to be expired
Thread.sleep(allowedInterval);
} catch (InterruptedException e) {
// We have been interrupted, get out of the loop.
return;
}
// now, remove all the sessions that have been created
// before the delay
long currentTime = System.currentTimeMillis();
lock.lock();
try {
Iterator<String> sessions = clients.keySet().iterator();
while (sessions.hasNext()) {
String session = sessions.next();
long creationTime = clients.get(session);
if (creationTime + allowedInterval < currentTime) {
clients.remove(session);
}
}
} finally {
lock.unlock();
}
}
}
/**
* Default constructor.
Sets the wait time to 1 second
*/
public ConnectionThrottleFilter() {
this(DEFAULT_TIME);
}
/**
* Constructor that takes in a specified wait time.
*
* @param allowedInterval
*
The number of milliseconds a client is allowed to wait
*
before making another successful connection
*
*/
public ConnectionThrottleFilter(long allowedInterval) {
this.allowedInterval = allowedInterval;
clients = new ConcurrentHashMap<String, Long>();
// Create the cleanup thread
ExpiredSessionThread cleanupThread = new ExpiredSessionThread();
// And make it a daemon so that it's killed when the server exits
cleanupThread.setDaemon(true);
// start the cleanuo thread now
cleanupThread.start();
}
/**
* Sets the interval between connections from a client.
* This value is measured in milliseconds.
*
* @param allowedInterval
*
The number of milliseconds a client is allowed to wait
*
before making another successful connection
*/
public void setAllowedInterval(long allowedInterval) {
lock.lock();
try {
this.allowedInterval = allowedInterval;
} finally {
lock.unlock();
}
}
/**
* Method responsible for deciding if a connection is OK
* to continue
*
* @param session
*
The new session that will be verified
* @return
*
True if the session meets the criteria, otherwise false
*/
protected boolean isConnectionOk(IoSession session) {
SocketAddress remoteAddress = session.getRemoteAddress();
if (remoteAddress instanceof InetSocketAddress) {
InetSocketAddress addr = (InetSocketAddress) remoteAddress;
long now = System.currentTimeMillis();
lock.lock();
try {
if (clients.containsKey(addr.getAddress().getHostAddress())) {
LOGGER.debug("This is not a new client");
Long lastConnTime = clients.get(addr.getAddress().getHostAddress());
clients.put(addr.getAddress().getHostAddress(), now);
// if the interval between now and the last connection is
// less than the allowed interval, return false
if (now - lastConnTime < allowedInterval) {
LOGGER.warn("Session connection interval too short");
return false;
}
return true;
}
clients.put(addr.getAddress().getHostAddress(), now);
} finally {
lock.unlock();
}
return true;
}
return false;
}
@Override
public void sessionCreated(NextFilter nextFilter, IoSession session) throws Exception {
if (!isConnectionOk(session)) {
LOGGER.warn("Connections coming in too fast; closing.");
session.close(true);
}
nextFilter.sessionCreated(session);
}
}