yweatherparser.java

yahoo 所使用的 天气预报的解析代码

/*
 * YWeatherParser.java
 *
 * Created on May 25, 2007, 2:37 PM
 *
 */

package yweatherbeta;

import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**
 *
 * @author BEN
 */
public class YWeatherParser {
    static char FAHRENHEIT = 'f';
    static char CELSIUS = 'c';
    static int TODAY = 0;
    static int TOMORROW = 1 ;
    private final String YWEATHER_PATH = "http://weather.yahooapis.com/forecastrss";
    private int unit;
    private String location;
    private DocumentBuilder builder;
    private XPath xpath;
    private Document doc;
    
    
    /**
     * Creates a new instance of YWeatherParser
     *
     * @param location The location of this forecast
     *
     */
    public YWeatherParser(String location) throws ParserConfigurationException{
        this(location, FAHRENHEIT);
    }
    /**
     * Creates a new instance of YWeatherParser
     *
     * @param location The location of this forecast
     * @param unit  Units for various aspects of the forecast.
     *
     */
    public YWeatherParser(String location, char unit) throws ParserConfigurationException{
        this.setLocation(location);
        if(unit != FAHRENHEIT && unit !=CELSIUS)
            throw(new IllegalArgumentException());
        this.setUnit(unit);
        DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
        domFactory.setNamespaceAware(true); // never forget this!
        this.builder = domFactory.newDocumentBuilder();
        XPathFactory factory = XPathFactory.newInstance();
        this.xpath = factory.newXPath();
        this.doc = null;
        xpath.setNamespaceContext(new YWeatherNamespaceContext());
    }
    
    public int getUnit() {
        return unit;
    }
    
    public void setUnit(int unit) {
        if(unit != FAHRENHEIT && unit !=CELSIUS)
            throw(new IllegalArgumentException());
        this.unit = unit;
    }
    
    public String getLocation() {
        return location;
    }
    
    public void setLocation(String location) {
        this.location = location;
    }
    
    public void parse() throws IOException, YWeatherParserException{
        try {
            this.doc = builder.parse("http://weather.yahooapis.com/forecastrss?p="+location+"&u="+unit);
            XPathExpression expr = xpath.compile("//title/text()");
            String result = (String) expr.evaluate(doc,XPathConstants.STRING);
            if(result.equals("Yahoo! Weather - Error"))
                throw new YWeatherParserException("Location or unit is not in database");
        } catch (XPathExpressionException ex) {
            //swallow this exception
        } catch (SAXException ex){
            throw new YWeatherParserException(ex.getMessage());
        }
    }
    
    public String getCity(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@city");
            returnValue = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getRegion(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@region");
            returnValue = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getLanguage(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//language/text()");
            returnValue = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public int getTTL(){
        int returnValue = 0;
        try {
            XPathExpression expr = xpath.compile("//ttl/text()");
            returnValue = new Integer((String) expr.evaluate(doc, XPathConstants.STRING));
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getCountry(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@country");
            returnValue = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getLastBuildDate(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//lastBuildDate/text()");
            returnValue = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public int getWindChill(){
        int returnValue = 0;
        try {
            XPathExpression expr = xpath.compile("//@chill");
            returnValue = new Integer((String) expr.evaluate(doc, XPathConstants.STRING));
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public int getWindDirection(){
        int returnValue = 0;
        try {
            XPathExpression expr = xpath.compile("//@direction");
            returnValue = new Integer((String) expr.evaluate(doc, XPathConstants.STRING));
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public int getWindSpeed(){
        int returnValue = 0;
        try {
            XPathExpression expr = xpath.compile("//@speed");
            NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
            returnValue = new Integer((String) nodes.item(1).getNodeValue());
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getDegreeUnit(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@distance");
            returnValue = (String)expr.evaluate(doc, XPathConstants.STRING);
            //returnValue = (char) Integer.parseInt(result);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getDistanceUnit(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@distance");
            returnValue = (String)expr.evaluate(doc, XPathConstants.STRING);
            //returnValue = (char) Integer.parseInt(result);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getPressureUnit(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@pressure");
            returnValue = (String)expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public String getSpeedUnit(){
        String returnValue = null;
        try {
            XPathExpression expr = xpath.compile("//@speed");
            returnValue = (String)expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public int getHumidity(){
        int returnValue = 0;
        try {
            XPathExpression expr = xpath.compile("//@humidity");
            returnValue = new Integer((String)expr.evaluate(doc, XPathConstants.STRING));
        } catch (XPathExpressionException ex) {
            //swallow exception
        }
        return returnValue;
    }
    
    public Forecast getForecast(int day) throws YWeatherParserException{
        Forecast forecast= new Forecast();
        if(day == TODAY){
            try {
                XPathExpression expr = xpath.compile("//yweather:forecast");
                NodeList result = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
                Node node  = result.item(0);
                forecast.setDay(node.getAttributes().getNamedItem("day").getNodeValue());
                forecast.setDate(node.getAttributes().getNamedItem("date").getNodeValue());
                forecast.setTempHigh(new Integer(node.getAttributes().getNamedItem("high").getNodeValue()));
                forecast.setTempLow(new Integer(node.getAttributes().getNamedItem("low").getNodeValue()));
                forecast.setCondition(node.getAttributes().getNamedItem("text").getNodeValue());
                forecast.setCode(new Integer(node.getAttributes().getNamedItem("code").getNodeValue()));
            } catch (XPathExpressionException ex) {
                //swallow exception
            }
        }else if (day == TOMORROW){
            try{
                XPathExpression expr = xpath.compile("//yweather:forecast");
                NodeList result = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
                Node node  = result.item(1);
                forecast.setDay(node.getAttributes().getNamedItem("day").getNodeValue());
                forecast.setDate(node.getAttributes().getNamedItem("date").getNodeValue());
                forecast.setTempHigh(new Integer(node.getAttributes().getNamedItem("high").getNodeValue()));
                forecast.setTempLow(new Integer(node.getAttributes().getNamedItem("low").getNodeValue()));
                forecast.setCondition(node.getAttributes().getNamedItem("text").getNodeValue());
                forecast.setCode(new Integer(node.getAttributes().getNamedItem("code").getNodeValue()));
            } catch (XPathExpressionException ex) {
                //swallow exception
            }
        }else
            throw new YWeatherParserException("Day format is wrong");               
        return forecast;
    }
}