30.2. Protocol Faults

Overview

Protocol exceptions are thrown when an error occurs during the processing of a request. All synchronous remote invocations can throw a protocol exception. The underlying cause occurs either in the consumer's message handling chain or in the service provider.
The JAX-WS specification defines a generic protocol exception. It also specifies a SOAP-specific protocol exception and an HTTP-specific protocol exception.

Types of protocol exceptions

The JAX-WS specification defines three types of protocol exception. Which exception you catch depends on the transport and binding used by your application.
Table 30.2, “Types of Generic Protocol Exceptions” describes the three types of protocol exception and when they are thrown.

Table 30.2. Types of Generic Protocol Exceptions

Exception ClassWhen Thrown
javax.xml.ws.ProtocolExceptionThis exception is the generic protocol exception. It can be caught regardless of the protocol in use. It can be cast into a specific fault type if you are using the SOAP binding or the HTTP binding. When using the XML binding in combination with the HTTP or JMS transports, the generic protocol exception cannot be cast into a more specific fault type.
javax.xml.ws.soap.SOAPFaultExceptionThis exception is thrown by remote invocations when using the SOAP binding. For more information see the section called “Using the SOAP protocol exception”.
javax.xml.ws.http.HTTPExceptionThis exception is thrown when using the Apache CXF HTTP binding to develop RESTful Web services. For more information see Part VI, “Developing RESTful Web Services”.

Using the SOAP protocol exception

The SOAPFaultException exception wraps a SOAP fault. The underlying SOAP fault is stored in the fault field as a javax.xml.soap.SOAPFault object.
If a service implementation needs to throw an exception that does not fit any of the custom exceptions created for the application, it can wrap the fault in a SOAPFaultException using the exceptions creator and throw it back to the consumer. Example 30.1, “Throwing a SOAP Protocol Exception” shows code for creating and throwing a SOAPFaultException if the method is passed an invalid parameter.

Example 30.1. Throwing a SOAP Protocol Exception

public Quote getQuote(String ticker)
{
  ...
  if(tickers.length()<3)
  {
    SOAPFault fault = SOAPFactory.newInstance().createFault();
    fault.setFaultString("Ticker too short");
    throw new SOAPFaultException(fault);
  }
  ...
}
When a consumer catches a SOAPFaultException exception they can retrieve the underlying cause of the exception by examining the wrapped SOAPFault exception. As shown in Example 30.2, “Getting the Fault from a SOAP Protocol Exception”, the SOAPFault exception is retrieved using the SOAPFaultException exception's getFault() method.

Example 30.2. Getting the Fault from a SOAP Protocol Exception

...
try
{
  proxy.getQuote(ticker);
}
catch (SOAPFaultException sfe)
{
  SOAPFault fault = sfe.getFault();
  ...
}