IncludeProperties within Json plugin are not handled properly with patterns including arrays

In order to repeat the error (on version struts2-json-plugin-2.1.8 ) it's enough to use a regexp pattern like this(in general the use of array [\d+] should be not at the first level, but deeper):
<param name="includeProperties">
operatorsgrid\.items[\d+]\.name
</param>
This pattern aims to extract a name property given this structure:
1)The Action has a getter:
OperatorsDTO getOperatorsgrid(){};
2)OperatorsDTO is defined as:
class OperatorsDTO{
public List<Operators> getItems(){}
}
3)Each Operator bean has (among others) a getName() method returning a String

With this configuration, the JSON created will be empty (just {"operatorsgrid":{}} ).
The problem has to be found in the method setIncludeProperties() of org.apache.struts2.json.JSONResult class
Given the above regexp, this method produces this list of patterns:
[operatorsgrid, opera, operatorsgrid\.items[\d+], operatorsgrid\.items[\d+]\.name]
Clearly there is the lack of one fundamental item: operatorsgrid\.items . Without this, the property items won't be explored. moreover there is another item "opera" which apparently is meaningless.
The error is at line 160:
this.includeProperties.add(Pattern.compile(patternExpr.substring(0, patternPiece
.lastIndexOf("
["))));
patternPiece is already a substring of patternExpr (line 151) so if this lines aims to add a new pattern which just excludes the las [\d+], it should be changed to:
this.includeProperties.add(Pattern.compile(patternExpr.substring(0, patternExpr
.lastIndexOf("
["))));
Given this, the new pattern set becomes:
[operatorsgrid, operatorsgrid\.items, operatorsgrid\.items[\d+], operatorsgrid\.items[\d+]\.name]
now the "opera" is vanished while we have operatorsgrid\.items which allows to dig into Operators bean.