异步DNS解析的实现

class ResolveThread extends Thread {
private Message query;
private Object id;
private ResolverListener listener;
private Resolver res;
/** Creates a new ResolveThread */
public ResolveThread(Resolver res, Message query, Object id, ResolverListener listener){
    this.res = res;
    this.query = query;
    this.id = id;
    this.listener = listener;
}
/**
 * Performs the query, and executes the callback.
 */
public void run() {
    try {
        Message response = res.send(query);
        listener.receiveMessage(id, response);
    }
    catch (Exception e) {
        listener.handleException(id, e);
    }
}
}