[rules-dev] Enum types in rules template
Hi all,
I got a question relating to value substitution of enum types in rule
templates.
Given the enum type:
public enum MyEnum
{
A("a");
B("b);
private String shortName;
private MyEnum(string shortName)
{
this.shortName = shortName;
}
public String shortName()
{
return shortName;
}
public String toString()
{
return shortName;
}
}
an object for the template
public class RuleObject
{
private MyEnum myEnum;
public TemplateObject(MyEnum myEnum)
{
this.myEnum = myEnum;
}
public void setMyEnum(MyEnum myEnum){this.myEnum = myEnum;}
public MyEnum getMyEnum(){ return myEnum;}
}
and a fact model object
public class FactObject
{
private MyEnum myEnum;
public void setMyEnum(MyEnum myEnum){this.myEnum = myEnum;}
public MyEnum getMyEnum(){ return myEnum;}
}
with an instance
TemplateObject templateObject = new TemplateObject(MyEnum.A);
and the template
----------------------------------
template header
name
myEnum
package my.package
import my.package.FactObject
import my.package.MyEnum
template "MyTemplate"
rule "@{name}"
when
$factObject: FactObject(myEnum == MyEnum.@{myEnum}} //<------------
toString() is used here
then
...
end
end template
----------------------------
It seems that for the substitution of @{myEnum} the toString() method of the
myEnum-Object is used. Without providing a toString() method in the declared
enum class the name() method is invoked implicitly. Hence the expression would
be substituted with 'A' ($factObject: FactObject(myEnum == A) . Therefore it's
necessary to put the Enums-Classname with a dot - "MyEnum." - in front so it
would be MyEnum.A in the generated rule ($factObject: FactObject(myEnum ==
MyEnum.A).
Trouble starts if I provide a custom toString() method in my enum type. With
the example above the expression @{myEnum} would be substituted with 'a'
($factObject: FactObject(myEnum == MyEnum.a) hence I get
MyEnum.a in my generated rule -> Rule error because type doesn't exist.
I don't know anything about the implementation details of the template to rule
generation - but wouldn't it make more sense
1. to substitute @{myEnum} with the enums classname and name() value
(@{myEnum} -> MyEnum.A) if the given field is an Enum instance?
or
2. At least use the name() method (which is final) to always get the enums
Name.
Maybe there are reasons why this makes no sense or can't be done? Your
thoughts please.
Cheers
Florian Beckmann
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florian.beckmann(a)camunda.com
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