[rules-users] Problem in using genrics with drools4.0.1.

[Gaurav2007]

HI ALL,

I am using drool 4.0.1 in my project.
I am facing problem in using generics feature of jdk1.5.

My objective is to perform validation on the basis of data type of variable.
for storing values of variable i have one Attribute Class it contains getter
setter for values of attribute and attributeId which is a string but value
of attribute is of deferent type so i am thinking to use generics here.

public class Attribute<T> {
    
    public String qualifiedName;

    public T newValue;

    public T oldValue;

    public String getQualifiedName() {
        return qualifiedName;
    }

    public void setQualifiedName(String qualifiedName) {
        this.qualifiedName = qualifiedName;
    }

    public T getNewValue() {
        return (T)newValue;
    }

    public void setNewValue(T newValue) {
        this.newValue = newValue;
    }

    public T getOldValue() {
        return oldValue;
    }

    public void setOldValue(T oldValue) {
        this.oldValue = oldValue;
    }
}


my rule for date comparison looks like:

//Date Comparison.
rule "W250.1 DateComparison"
	when
		$dto : DataProvider()
	Attribute(newValue < "29-Oct-2007") from $dto.getValue("W250.1")
	then
		System.out.println ("Error in Date check \t");
end

DataProvider class it is responsible to give instance of attribute
corresponding to attributeId:

public class DataProvider {
    
    HashMap<String,Attribute> fieldMap=new HashMap<String, Attribute>();
    
    public DataProvider() {
        populateMap();
    }
    
    public Attribute  getValue(String qualifiedName){
            Attribute attribute = fieldMap.get(qualifiedName);
            return attribute;
    }
    
    public void populateMap(){
        Attribute<Date> attribute = new Attribute<Date>();
        SimpleDateFormat format = new SimpleDateFormat("dd-MMM-yyyy");
           Date date;
        try {
            date = format.parse("27-Oct-2007");
            attribute.setQualifiedName("W250.1");
            attribute.setOldValue(date);
            attribute.setNewValue(date);
            fieldMap.put(attribute.getQualifiedName(),attribute);
            
        }
        catch (ParseException e) {
            e.printStackTrace();
        }

    }
}

in this case i am getting exception:
Exception in thread "main" java.lang.ClassCastException: java.lang.String

when i am not using generics this rule is working fine.
but in this case how should i perform validation depending upon data type of
attribute.

can you please help me in solving this problem.

Thanks,
Gaurav Joshi

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