[engine] implements new strategy for reference boolean evaluation

1) return false for a null object

2) return its value for a Boolean object, or the result of the getAsBoolean() method if it exists.

3) If directive.if.emptycheck = false (true by default), stop here and return true.

4) check for emptiness:
  - return whether an array is empty.
  - return whether isEmpty() is false (covers String and all Collection classes).
  - return whether length() is zero (covers CharSequence classes other than String).
  - returns whether size() is zero.
  - return whether a Number *strictly* equals zero.

5) check for emptiness after explicit conversion methods:
  - return whether the result of getAsString() is empty (and false for a null result) if it exists.
  - return whether the result of getAsNumber() *strictly* equals zero (and false for a null result) if it exists. 





git-svn-id: https://svn.apache.org/repos/asf/velocity/engine/trunk@1783739 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 9 insertions, 0 deletions

diff --git a/velocity-engine-core/src/main/resources/org/apache/velocity/runtime/defaults/velocity.properties b/velocity-engine-core/src/main/resources/org/apache/velocity/runtime/defaults/velocity.properties
index 3f416a62..c1ff863a 100644
--- a/velocity-engine-core/src/main/resources/org/apache/velocity/runtime/defaults/velocity.properties
+++ b/velocity-engine-core/src/main/resources/org/apache/velocity/runtime/defaults/velocity.properties
@@ -44,6 +44,15 @@ runtime.string.interning = true
 directive.foreach.maxloops = -1
 
 # ----------------------------------------------------------------------------
+# I F  P R O P E R T I E S
+# ----------------------------------------------------------------------------
+# This property controls whether empty strings and collections,
+# as long as zero numbers, do evaluate to false.
+# ----------------------------------------------------------------------------
+
+directive.if.emptycheck = true
+
+# ----------------------------------------------------------------------------
 # I N C L U D E  P R O P E R T I E S
 # ----------------------------------------------------------------------------
 # These are the properties that governed the way #include'd content