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      1 // Licensed under Apache License version 2.0
      2 package javax.jmdns.impl.tasks.resolver;
      3 
      4 import java.io.IOException;
      5 import java.util.Timer;
      6 import java.util.logging.Level;
      7 import java.util.logging.Logger;
      8 
      9 import javax.jmdns.impl.DNSOutgoing;
     10 import javax.jmdns.impl.JmDNSImpl;
     11 import javax.jmdns.impl.constants.DNSConstants;
     12 import javax.jmdns.impl.tasks.DNSTask;
     13 
     14 /**
     15  * This is the root class for all resolver tasks.
     16  *
     17  * @author Pierre Frisch
     18  */
     19 public abstract class DNSResolverTask extends DNSTask {
     20     private static Logger logger = Logger.getLogger(DNSResolverTask.class.getName());
     21 
     22     /**
     23      * Counts the number of queries being sent.
     24      */
     25     protected int         _count = 0;
     26 
     27     /**
     28      * @param jmDNSImpl
     29      */
     30     public DNSResolverTask(JmDNSImpl jmDNSImpl) {
     31         super(jmDNSImpl);
     32     }
     33 
     34     /*
     35      * (non-Javadoc)
     36      * @see java.lang.Object#toString()
     37      */
     38     @Override
     39     public String toString() {
     40         return super.toString() + " count: " + _count;
     41     }
     42 
     43     /*
     44      * (non-Javadoc)
     45      * @see javax.jmdns.impl.tasks.DNSTask#start(java.util.Timer)
     46      */
     47     @Override
     48     public void start(Timer timer) {
     49         if (!this.getDns().isCanceling() && !this.getDns().isCanceled()) {
     50             timer.schedule(this, DNSConstants.QUERY_WAIT_INTERVAL, DNSConstants.QUERY_WAIT_INTERVAL);
     51         }
     52     }
     53 
     54     /*
     55      * (non-Javadoc)
     56      * @see java.util.TimerTask#run()
     57      */
     58     @Override
     59     public void run() {
     60         try {
     61             if (this.getDns().isCanceling() || this.getDns().isCanceled()) {
     62                 this.cancel();
     63             } else {
     64                 if (_count++ < 3) {
     65                     if (logger.isLoggable(Level.FINER)) {
     66                         logger.finer(this.getName() + ".run() JmDNS " + this.description());
     67                     }
     68                     DNSOutgoing out = new DNSOutgoing(DNSConstants.FLAGS_QR_QUERY);
     69                     out = this.addQuestions(out);
     70                     if (this.getDns().isAnnounced()) {
     71                         out = this.addAnswers(out);
     72                     }
     73                     if (!out.isEmpty()) {
     74                         this.getDns().send(out);
     75                     }
     76                 } else {
     77                     // After three queries, we can quit.
     78                     this.cancel();
     79                 }
     80             }
     81         } catch (Throwable e) {
     82             logger.log(Level.WARNING, this.getName() + ".run() exception ", e);
     83             this.getDns().recover();
     84         }
     85     }
     86 
     87     /**
     88      * Overridden by subclasses to add questions to the message.<br/>
     89      * <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
     90      *
     91      * @param out
     92      *            outgoing message
     93      * @return the outgoing message.
     94      * @exception IOException
     95      */
     96     protected abstract DNSOutgoing addQuestions(DNSOutgoing out) throws IOException;
     97 
     98     /**
     99      * Overridden by subclasses to add questions to the message.<br/>
    100      * <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
    101      *
    102      * @param out
    103      *            outgoing message
    104      * @return the outgoing message.
    105      * @exception IOException
    106      */
    107     protected abstract DNSOutgoing addAnswers(DNSOutgoing out) throws IOException;
    108 
    109     /**
    110      * Returns a description of the resolver for debugging
    111      *
    112      * @return resolver description
    113      */
    114     protected abstract String description();
    115 
    116 }
    117