Chapter 3 Service Endpoint Design
81
A Web service application may encounter two types of error conditions. One
type of error might be an irrecoverable system error, such as an error due to a
network connection problem. When an error such as this occurs, the JAX RPC
runtime on the client throws the client platform's equivalent of an irrecoverable
system exception. For Java clients, this translates to a 
RemoteException
.
A Web service application may also encounter a recoverable application error
condition. This type of error is called a service specific exception. The error is
particular to the specific service. For example, a weather Web service might indi 
cate an error if it cannot find weather information for a specified city.
To illustrate the Web service exception handling mechanism, let's examine it
in the context of the weather Web service example. When designing the weather
service, you want the service to be able to handle a scenario in which the client
requests weather information for a nonexistent city. You might design the service
to throw a service specific exception, such as 
CityNotFoundException
, to the
client that made the request. You might code the service interface so that the
getWeather
 method throws this exception. (See Code Example 3.9.)
public interface WeatherService extends Remote {
public String getWeather(String city) throws 
CityNotFoundException, RemoteException;
}
Code Example 3.9
Throwing a Service Specific Exception
Service specific exceptions like 
CityNotFoundException
, which are thrown
by the Web service to indicate application specific error conditions, must be
checked exceptions that directly or indirectly extend 
java.lang.Exception
. They
cannot be unchecked exceptions. Code Example 3.10 shows a typical implemen 
tation of a service specific exception, such as for 
CityNotFoundException
.
public class CityNotFoundException extends Exception {
private String message;
public CityNotFoundException(String message) {
super(message);
this.message = message;
}
public String getMessage() {
return message;
<





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