Backport "Avoid infinite loop in AbstractResource#contentLength" [SPR-9163]

[spring-projects-issues]

Chris Beams opened SPR-9163 and commented

---

This issue is a backport sub-task of #13799

Referenced from: commits 40a6769

[spring-projects-issues]

Chris Beams commented

commit 40a6769309dfcc32e93072769fba2a46dd0e6a0f (HEAD, springsource/3.1.x, 3.1.x)
Author: Chris Beams <cbeams@vmware.com>
Date:   Fri Feb 24 14:29:28 2012 +0100

    Avoid infinite loop in AbstractResource#contentLength
    
    Due to changes made in commit 2fa87a71 for SPR-9118,
    AbstractResource#contentLength would fall into an infinite loop unless
    the method were overridden by a subclass (which it is in the majority of
    use cases).
    
    This commit:
    
     - fixes the infinite recursion by refactoring to a while loop
    
     - asserts that the value returned from #getInputStream is not null in
       order to avoid NullPointerException
    
     - tests both of the above
    
     - adds Javadoc to the Resource interface to clearly document that the
       contract for any implementation is that #getInputStream must not
       return null
    
    Issue: SPR-9163
    Backport-Issue: SPR-9161
    Backport-Commit: 7ca5fba05ff0ef4dcf076303e1cba19c4b771d94