Grails error handler always receives null pointer

问题

We have a custom error controller that gets called after all of our errors. However, most of our errors that get thrown end up coming into the controller as null pointers, even though the original error was not a null pointer. Any ideas? Code below. Bootstrap and UrlMappings available if needed. Thanks

Error Handler method

def HandleErrors =
{

    def exception = request.exception.cause.class  

    if (exception) 
    { 
        Exception ex = request.exception  //This exception is always a NPE
            ...

Block of code throwing the exception. I originally did not have a try catch in here, but wanted to add it so that I was sure the exception being thrown was Not a NPE. Its a file not found exception.

try{
        def writer = new FileWriter( new File(fileSaveLocation));
    } 
    catch ( ex)
    {
        throw(ex)
    }

Edit: Adding the exception that is pushed to the exception handler

Exception:org.codehaus.groovy.grails.web.errors.GrailsWrappedRuntimeException
Cause:org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException

回答1:

It's not because you're referencing something that is null inside the error handler, and so are inadvertently throwing another exception, which is again caught?

can you try changing:

def exception = request.exception.cause.class  

to

def exception = request?.exception?.cause?.class  

来源：https://stackoverflow.com/questions/6777000/grails-error-handler-always-receives-null-pointer