I have to retrieve a set of column values from D/B and check it as a condition.
For example, I will have strings like "value > 2"
, "4 < value < 6"
in a D/B column. (value is the one which is compared all the time). I will have a variable value declared in my code and I should evaluate this condition.
int value = getValue();
if (value > 2) //(the string retrieved from the D/B)
doSomething();
How can I do this?? Any help is muceh appreciated. Thanks.
You should try parsing the string inside the if statement by doing something like
In parseMyString can determine what you need to evaluate for the condition. If you don't know how to create a parser then take a look at: http://www.javapractices.com/topic/TopicAction.do?Id=87
You are basically evaluating a scripted expression. Depending what is allowed in that expression, you can get away with something very simple (regular expression identifying the groups) or very complex (embed a javascript engine?).
I'm assuming you're looking at the simple case, where the expression is: [boundary0] [operator] "value" [operator] [boundary1]
Where one, but not both of the [boundary] [operator] groups might be omitted. (And if both are presents, operator should be the same)
I would use a regular expression for that with capturing groups.
Something like: (?:(\d+)\s*([<>])\s*)?value(?:\s*([<>])\s*(\d+))?
And then: boundary1 = group(1); operator1 = group(2); operator2 = group(3); boundary2 = group(4)