Throwable as first argument of explicit recover method should be optional

[quaff]

According to Javadoc of @recover, The Throwable first argument is optional. Before this commit,

java.lang.NullPointerException: Cannot invoke "java.lang.Class.isAssignableFrom(java.lang.Class)" because "meta.type" is null
	at org.springframework.retry.annotation.RecoverAnnotationRecoveryHandler.findClosestMatch(RecoverAnnotationRecoveryHandler.java:154)
	at org.springframework.retry.annotation.RecoverAnnotationRecoveryHandler.recover(RecoverAnnotationRecoveryHandler.java:75)
	at org.springframework.retry.interceptor.RetryOperationsInterceptor$ItemRecovererCallback.recover(RetryOperationsInterceptor.java:159)
	at org.springframework.retry.support.RetryTemplate.handleRetryExhausted(RetryTemplate.java:543)
	at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:389)
	at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:225)
	at org.springframework.retry.interceptor.RetryOperationsInterceptor.invoke(RetryOperationsInterceptor.java:124)
	at org.springframework.retry.annotation.AnnotationAwareRetryOperationsInterceptor.invoke(AnnotationAwareRetryOperationsInterceptor.java:160)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750)

is raised for

@Retryable(retryFor = RuntimeException.class, recover = "recover")
public String service(String param) {
	throw new RuntimeException("Planned");
}

@Recover
public String recover(String param) {
	return param;
}

[artembilan]

LGTM.

@garyrussell ?

[garyrussell]

Fine with me; it's a bit unusual to not expose the exception type to the recoverer, but there's no harm in this.

[artembilan]

@quaff ,

Thank you very much for contribution; looking forward for more!