refundant nullcheck of value known to non-null

[hqq2023623]

There are some "refundant nullcheck of value known to non-null" suggests can be found by findBugs plugin, maybe we should handle these to make the code cleaner
example : CacheFilter#invoke , check the (cache != null) twice

[ralf0131]

Hi, could you provide more details (file name, line number for example)?

[hqq2023623]

type1 : check null more than one time

FutureFilter#fireInvokeCallback

line 110 ， onInvokeMethod is checked by line 107

the same as FutureFilter#fireReturnCallback

### and FutureFilter#fireThrowCallback

type2 : checked by context

MergeableClusterInvoker#invoke ,at line 144

returnType.getMethod() will not return null

JavaBeanDescriptor#getEnumPropertyName , at line 141

if getProperty() return null , then toString() may throw NPE before the result == null check

[hqq2023623]

type3 : call method that never return null

###ExtensionLoader#hasExtension , at line 333

ExtensionLoader#getExtensionClass() never return null

[hqq2023623]

type4 : check by both caller and self

caller : RegistryDirectory#notify , at line 207

self : RegistryDirectory#toRouters , at line 309

[hqq2023623]

@ralf0131

[ralf0131]

Hi @hqq2023623 Thanks for pointing out. It will be really appreciate if you can create a pull request~

[chickenlj]

Thanks, i will review the PR laterly.