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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:
WSDL URL
http://www.xmethods.net/sd/2001/CurrencyExchangeService.wsdl
Operation
getRate
Input message parts
Country1 (a string), country 2 (a string)
Output message name
Result
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 Code
As 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 messagesusers 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 Hack
As 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
