Error Handling REST ful WebServices

Looks to be a Easy One but Really Not.

Like Anyone before doing something i read many documents and referrred many REST webserivces api in the market by leading companies.

And there is no common practice.It purely depends on the Architect/Designer of the System.

for eg: Ebay returns a status code HTTP 200 OK in case of request error(eg :request element is not formatted as expected) and then a Custom Error Code. which is not so correct in my View.

Anything which is 200 OK is considered as SUCCESS as per HTTP Spec, and for application which are created with HTTP Awareness. the above apporoach may defeat that. Still i understand there should be a strong reason why ebay did that ...

OK coming back to Error Handling..

a. Create a error schema or object ( with complex type customcode, error classification,Message) you can keep it simple like this or you can even return the error param.

b. inside the catch block set the appropriate values for that error conditions.

c. Set the HTTP Status to appropriate status, if the Error Classification is Request ERROR.(i use http 400 for this)

How to Classify ?

Any Problem in the Request Data can be considered as REQUEST ERROR

if valid Request data, Any Problem while processing the Request is a APPLICATION ERROR. (this error includes business rule violations)


if Required Have another classification for SYSTEM ERROR

A Very important Rule is Never /Ever Let your application to expose a stack trace to client. Your application should handle and all the Errors and Exceptions and return specific code/Generic code . Make Sure you Log the Details on the Server.


Please let me know if you have any questions.

Thanks
Premkumar.

RestEasy - Not Easy for Validation

After a Long time i am back to my Blog to post my findings on REST easy and Rest ful web services implementation practices.

Though my Preference is' Jersey ' i was in a position to select Resteasy for the implementation

The documentation explains about Decorators for Validation. it applies only for Marhsalling. for unmarshaling there are no decorators available in the framework.
Writing a New Decorator for unmarshaling is not an easy task.

So i used a Validator class from javax.xml.bind.* which worked perfectly.

But the Trick Here is you cannot Validate and let the framework bind on the same input Stream .so you need to clone the input stream ,one for validation and the other one for binding. (this binding will be done by Rest easy framework)

This worked really well.

Code to clone Input Stream

org.apache.commons.io.IOUtils;

private List cloneInputStream(InputStream iStream) {
List inArray = null;
List errorList = new ArrayList();
try {

if (iStream != null) {
String base = org.apache.commons.io.IOUtils.toString(iStream);
logger.debug("called cloneInputStream: input stream content -> {}",
base);
inArray = new ArrayList();
for (int i = 0;
i < APIConstants.INPUTSTREAM_CLONES; i++) {
inArray.add(IOUtils.toInputStream(base));
}
}
return inArray;
}
Please let me know if you have any questions.

Thanks
Premkumar