ratehelper.java

来自「JAVA Servlet2.3外文书籍源码」· Java 代码 · 共 93 行

//== save as RateHelper.java
import java.io.*;
import java.net.*;
import java.util.*;
import org.apache.soap.*;
import org.apache.soap.rpc.*;

public class RateHelper {
  private static Hashtable rate_table = new Hashtable(11);

  public static String getExchangeRate(String country) {
    Double rate = (Double)rate_table.get(country);
    if( rate != null ) {
      return rate.toString() + "(old)";
    } else {
      try {
        rate = callExchangeRateService( country );
        return rate.toString() + "(new)";
      } catch( Exception e ) {
        return e.getMessage();
      }
    }
  }

  public static double getRate(String country) {
    Double rate = (Double)rate_table.get(country);
    if(rate == null) {
      try {
        rate = callExchangeRateService( country );
      } catch(Exception e) {
        rate = new Double(0.0);
      }
    }
    return rate.doubleValue();
  }

  public static double getRate(String country1, String country2) {
    double rval;
    double currency1_per_usdollar = getRate( country1 );
    double currency2_per_usdollar = getRate( country2 );

    if(currency2_per_usdollar > 0.0) {
      rval = currency1_per_usdollar/currency2_per_usdollar;
    } else {
      rval = 0.0;
    }
    return rval;
  }

  public static String getExchangeRate(String country1, String country2) {
    double rate = getRate(country1, country2);
    return Double.toString(rate);
  }

  public static synchronized Double callExchangeRateService(String country)
      throws Exception {
    //== just in case the last guy got it while we were waiting
    Double rate = (Double)rate_table.get(country);
    if(rate != null) {
      return rate;
    }
    
    try{
      URL url = new URL( "http://localhost:8088/soap/servlet/rpcrouter" );
      String encodingStyleURI = Constants.NS_URI_SOAP_ENC;
      URLConnection connection = url.openConnection();
      // Build the call.
      Call call = new Call ();
      call.setTargetObjectURI ("SoapExchangeRate");
      call.setMethodName ("getExchangeRate");
      Vector params = new Vector ();
      call.setEncodingStyleURI(encodingStyleURI);
      params.addElement(new Parameter("country", String.class, country, null));
      call.setParams (params);
      Response resp = call.invoke (url, "");
      if (resp.generatedFault ()) {
        Fault fault = resp.getFault ();
        String faultString = fault.getFaultString ();
        System.out.println( faultString );
      } else {
        Parameter result = resp.getReturnValue ();
        rate = (Double)result.getValue();
        rate_table.put(country, rate);
        return rate;
      }  
    } catch(Exception e) {
      throw(e);
    }
    return rate;
  }
}