Catch parameter parsing exception in Spring 3.0 WebMVC

I use Spring WebMVC to provide a REST API. I use methods like

@RequestMapping("/path({id}") void getById(@PathVariable("id") int id) {} methods.

When the client incorrectly put a string instead of an integer id into the query, I get a NumberFormatException like:

java.lang.NumberFormatException: For input string: "dojo"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
    at java.lang.Long.parseLong(Long.java:410)
    at java.lang.Long.valueOf(Long.java:525)
    at org.springframework.util.NumberUtils.parseNumber(NumberUtils.java:158)
    at org.springframework.core.convert.support.StringToNumberConverterFactory$StringToNumber.convert(StringToNumberConverterFactory.java:59)
    at org.springframework.core.convert.support.StringToNumberConverterFactory$StringToNumber.convert(StringToNumberConverterFactory.java:1)
    at org.springframework.core.convert.support.GenericConversionService$ConverterFactoryAdapter.convert(GenericConversionService.java:420)
    at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:37)
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:135)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:199)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:104)
    at org.springframework.beans开发者_JAVA百科.SimpleTypeConverter.convertIfNecessary(SimpleTypeConverter.java:47)
    at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:526)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolvePathVariable(HandlerMethodInvoker.java:602)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:289)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:163)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:414)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:402)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)

My Question is now, how can I elegantly catch it? I know that Spring provides @ExeptionHandler annotations but I don't want to catch the NFE in general. I want to be able to catch all parsing exception in order to present a nice error message to the client.

Any ideas?

Cheers,

Jan

Is that the actual exception? (it doesn't match your code example) Normally one would expect that to be wrapped in org.springframework.beans.TypeMismatchException which is probably specific enough that you could write an @ExceptionHandler method for it.

If that's not specific enough, you will need to forgo the Spring-Magic and just change the parameter type to String + parse it yourself. Then you can handle it any way you like.

I have found solution for your problem here http://www.coderanch.com/t/625951/Spring/REST-request-mapping-parameter-type

Just try

@RequestMapping("/path({id:[\\d]+}") void getById(@PathVariable("id") int id) {} methods.

And then not valid usage will cause 404. I'm not sure if version 3.0 supports this.

I am not 100% sure about whether this works for @PathVaribale or not, but generally for model binding you could use a BindingResult object next to your path variable and model and parsing error will be added to the BindingResult/Errors object.

Perhaps I do this because I am an old tyme programmer, but I use String as the type for all @PathVariable and @RequestParameter parameters then I do the parsing inside the handler method. This allows me to easily catch all NumberFormatException exceptions.

Although this is not the "Spring" way of doing this, I recommend it because it is easy for me and easy for my future offshore maintenance programmers to understand.

putting your comments together, I tried the following:

public class ValidatingAnnotationMethodHandlerAdapter extends AnnotationMethodHandlerAdapter {

@Override
protected ServletRequestDataBinder createBinder(HttpServletRequest request, Object target, String objectName) throws Exception {
    return new ServletRequestDataBinder(target, objectName) {

        @Override
        public <T> T convertIfNecessary(Object value, Class<T> requiredType) throws TypeMismatchException {
            try {
                return super.convertIfNecessary(value, requiredType);
            } catch (RuntimeException e) {
                throw new ControllerException("Could not parse parameter: " + e.getMessage());
            }
        }

        @Override
        public <T> T convertIfNecessary(Object value, Class<T> requiredType, MethodParameter methodParam) throws TypeMismatchException {
            try {
                return super.convertIfNecessary(value, requiredType, methodParam);
            } catch (RuntimeException e) {
                throw new ControllerException("Could not parse parameter: " + e.getMessage());
            }
        }

    };
}

ControllerException is a custom exception which is catched by an @ExceptionController annotated method (I use this exception in all validator classes).

Hope you like it,

Jan