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// Licensed under Apache License version 2.0
package javax.jmdns.impl.tasks.resolver;
import java.io.IOException;
import java.util.Timer;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.jmdns.impl.DNSOutgoing;
import javax.jmdns.impl.JmDNSImpl;
import javax.jmdns.impl.constants.DNSConstants;
import javax.jmdns.impl.tasks.DNSTask;
/**
* This is the root class for all resolver tasks.
*
* @author Pierre Frisch
*/
public abstract class DNSResolverTask extends DNSTask {
private static Logger logger = Logger.getLogger(DNSResolverTask.class.getName());
/**
* Counts the number of queries being sent.
*/
protected int _count = 0;
/**
* @param jmDNSImpl
*/
public DNSResolverTask(JmDNSImpl jmDNSImpl) {
super(jmDNSImpl);
}
/*
* (non-Javadoc)
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return super.toString() + " count: " + _count;
}
/*
* (non-Javadoc)
* @see javax.jmdns.impl.tasks.DNSTask#start(java.util.Timer)
*/
@Override
public void start(Timer timer) {
if (!this.getDns().isCanceling() && !this.getDns().isCanceled()) {
timer.schedule(this, DNSConstants.QUERY_WAIT_INTERVAL, DNSConstants.QUERY_WAIT_INTERVAL);
}
}
/*
* (non-Javadoc)
* @see java.util.TimerTask#run()
*/
@Override
public void run() {
try {
if (this.getDns().isCanceling() || this.getDns().isCanceled()) {
this.cancel();
} else {
if (_count++ < 3) {
if (logger.isLoggable(Level.FINER)) {
logger.finer(this.getName() + ".run() JmDNS " + this.description());
}
DNSOutgoing out = new DNSOutgoing(DNSConstants.FLAGS_QR_QUERY);
out = this.addQuestions(out);
if (this.getDns().isAnnounced()) {
out = this.addAnswers(out);
}
if (!out.isEmpty()) {
this.getDns().send(out);
}
} else {
// After three queries, we can quit.
this.cancel();
}
}
} catch (Throwable e) {
logger.log(Level.WARNING, this.getName() + ".run() exception ", e);
this.getDns().recover();
}
}
/**
* Overridden by subclasses to add questions to the message.<br/>
* <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
*
* @param out
* outgoing message
* @return the outgoing message.
* @exception IOException
*/
protected abstract DNSOutgoing addQuestions(DNSOutgoing out) throws IOException;
/**
* Overridden by subclasses to add questions to the message.<br/>
* <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
*
* @param out
* outgoing message
* @return the outgoing message.
* @exception IOException
*/
protected abstract DNSOutgoing addAnswers(DNSOutgoing out) throws IOException;
/**
* Returns a description of the resolver for debugging
*
* @return resolver description
*/
protected abstract String description();
}
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