cmdlineoutput.java

用于传感器网络的节点操作系统 TinyOS 结构设计非常有意思

package net.tinyos.tinydb;
import net.tinyos.tinydb.parser.*;
import java.util.*;

/** CmdLineOutput runs queries and displays results on the command line.
    @author Sam Madden ([e-mail])
*/
public class CmdLineOutput implements ResultListener {
    /** Constructor -- runs the specified query using the
	provided network interface.
	@param nw A network interface for talking with the basestation / 
	          parsing results.
	@param queryString the query to run.
    */
    public CmdLineOutput(TinyDBNetwork nw, String queryString) {
	try {
	    //parse the query
	    TinyDBQuery q = SensorQueryer.translateQuery(queryString, (byte)1);
	    Vector headings = q.getColumnHeadings(); //fetch the names of the fields in the result
	    
	    this.q = q;

	    TinyDBMain.notifyAddedQuery(q); // add query to list of known queries
	    nw.addResultListener(this, true, 1); // set ourselves up to receives results for query id 1

	    
	    System.out.print("|");
	    for (int i = 0; i < headings.size(); i++) {
		System.out.print("\t" + headings.elementAt(i) + "\t|");
	    }
	    System.out.println("\n-----------------------------------------------------");

	    nw.sendQuery(q); //inject the query

	    
	} catch (ParseException e) {
	    System.err.println("Invalid query : " + queryString + "(" + e + ")");
	} catch (java.io.IOException e) {
	    System.err.println("Network error: " + e);
	}
	
    }

    /** ResultListener method that is called whenever a query result arrives for us
	This method just prints each result out on the command line.
	@param qr A query result that just arrived 
    */
    public void addResult(QueryResult qr) {
	Vector v = qr.resultVector();
	for (int i = 0; i < v.size(); i++) {
	    System.out.print("\t" + v.elementAt(i) + "\t|");
	}
	System.out.println();

    }

    private TinyDBQuery q;
}