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< Day Day Up > |
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Hack 55 Convert Currency
Most people refer to a newspaper or web site to do currency conversions. Let an IRC bot using an appropriate Web Service do all the hard work for you. Using Web Services again, you can create an easy hack that will convert currencies. Users can enter the names of two countries and see the exchange rate or convert a specified amount from one currency to another. This hack uses another service provided by XMethods. As with the other two previous Web Services examples, you need four pieces of information:
A list of countries that can be used as inputs is provided near the end of this hack in Table 8-1. The first country is the currency you are converting from, and the second is the currency you are converting to. The conversion will relate one unit of currency from country1 to the calculated number of units of country2. 8.6.1 The CodeAs with the other Web Service hacks [Hacks Section 8.4#53 and Section 8.5#54], very few changes other than adjusting variable values are required. Following is the code for the CurrencyService class and its method to convert currencies: import java.util.*;
import samples.client.DynamicInvoker;
public class CurrencyService {
static String wsdlLocation =
"http://www.xmethods.net/sd/2001/CurrencyExchangeService.wsdl";
static String operationName= "getRate";
static String outputName = "Result";
static String portName = null;
public static String convert(String country1, String country2) {
String[] args =
new String[] {wsdlLocation, operationName, country1, country2};
try {
DynamicInvoker invoker=new DynamicInvoker(wsdlLocation);
HashMap map = invoker.invokeMethod(operationName, portName, args);
return map.get(outputName).toString( );
}catch (Exception e){return null;}
}
}You now have a working method for using the Web Service to convert currencies. Like the previous service hacks, it will use PircBot and add code to the onMessage method. You can build this hack on top of the basic example in [Hack #35] or continue building up a multifunctional Web Services bot based on the previous Web Services hack. The bot will handle two types of messages—users can get the exchange rate or convert a specific amount of currency. To get the exchange rate, the bot will read messages in the following format: WSBot, exchange COUNTRY1 to COUNTRY2 To process this request, you begin as with the previous example, using a StringTokenizer to parse the input: String query = t.nextToken( );
if (query.equals("exchange")) {
String response = "";The next step will be to pull out the two country names. This is not trivial because some countries have two words in their names (e.g., Sri Lanka). Thus, you cannot just pull single tokens. The following code shows how to find the names for both countries. Since the word "to" separates the country names, you can concatenate words until you find the "to": String country1 = t.nextToken( );
String next = t.nextToken( );
while (!next.equals("to")){
country1 = country1 + " " + next;
next = t.nextToken( );
}
String country2 = t.nextToken( );
while (t.hasMoreTokens( )) {
next = t.nextToken( );
country2 = country2 + " " + next;
}With the two country names taken care of, the only steps left are to call the Web Service and print an output message: sendMessage(channel, "Just a moment while I look that up...");
String result = CurrencyService.convert(country1, country2);
response = "1 unit of " + country1 + " currency is equal to ";
response = response + result + " units of " + country2 + " currency.";
}
sendMessage(channel, response);
}
...The second message will have an additional number, providing us with an amount to convert: WSBot, convert AMOUNT COUNTRY1 to COUNTRY2 The code for this conversion is almost identical to the exchange rate code. The additional step requires us to get the amount of currency being converted and then multiply it by the exchange rate. The following code is identical to the previous code, except for the bold lines: String query = t.nextToken( );
if (query.equals("convert")) {
String response = "";
String amount = t.nextToken( );
String country1 = t.nextToken( );
String next = t.nextToken( );
while (!next.equals("to")){
country1 = country1 + " " + next;
next = t.nextToken( );
}
String country2 = t.nextToken( );
while (t.hasMoreTokens( )){
next = t.nextToken( );
country2 = country2 + " " + next;
}
sendMessage(channel, "Just a moment while I look that up...");
String result = CurrencyService.convert(country1, country2);
double converted = Double.valueOf(amount).doubleValue( ) *
Double.valueOf(result).doubleValue( );
response = amount + " units of " + country1 + "
currency is equal to ";
response += converted + " units of " + country2 + " currency.";
}
sendMessage(channel, response);
}8.6.2 Running the HackAs with the previous Web Services hacks, you will need to ensure that you have all of the Axis components in your classpath when you compile the bot: % javac -classpath .:pircbot.jar:axis-1_1/lib/axis.jar: \ axis-1_1/lib/axis-ant.jar: \ axis-1_1/lib/commons-discovery.jar:axis-1_1/lib/commons-logging.jar: \ axis-1_1/lib/jaxrpc.jar:axis-1_1/lib/log4j-1.2.8.jar:axis-1_1/lib/saaj.jar:\ axis-1_1/lib/wsdl4j.jar *.java Depending on the name of your main class, you can then run the bot like so: % java -classpath .:pircbot.jar:axis-1_1/lib/axis.jar: \ axis-1_1/lib/axis-ant.jar: \ axis-1_1/lib/commons-discovery.jar:axis-1_1/lib/commons-logging.jar: \ axis-1_1/lib/jaxrpc.jar:axis-1_1/lib/log4j-1.2.8.jar:axis-1_1/lib/saaj.jar:\ axis-1_1/lib/wsdl4j.jar Main Replace Main with the correct name for your main class if it is different. The conversions, shown in Figure 8-7, are quick and easy and can be requested by anyone in the same channel as the bot. Figure 8-7. The Web Service bot performing currency conversions Table 8-1 shows the list of supported countries for use with the currency conversion bot. For example, to convert 10 U.S. dollars to U.K. pounds, you say: WSBot, convert 10 us to uk and the bot will respond with: <WSBot> Just a moment while I look that up... <WSBot> 10 units of currency from us is equal to 5.60108 units of uk currency.
Now when someone's boasting about how little they paid for a new CD when they were on holiday abroad, you can use this bot to find out what the equivalent amount is in your country. —Jennifer Golbeck |
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