In Mina 2 we can add attributes to a session and get them as well.
Because IoSession#getAttribute(Object
key) returns Object we always have to remember what attribute type is
associated with the key and cast the result to the expected type.
Mina 2 example:
final static Object KEY = new AttributeKey(SourceClass.class,"myKey");
...
session.set(KEY,"myAttribute");
String attributeValue= (String)session.get(KEY);
Instead of using plain Object-keys, the key type should contain information
about its attributes. The aim is to get type-safe access to attributes.
Assume we have the following new AttributeKey-Class:
/**
* @parmeter T Type of the referenced Attribute
*/
class AttributeKey<T> {
public TypesafeAttributeKey(Class<T> attributeType, String attributeKey){
...
}
}
The IoSession should have Attribute related accessors like these:
void setAttribute(AttributeKey<T> key, T value);
T getAttribute(AttributeKey<T> key);
So in Mina 3 the example could look like this:
final static AttributeKey<String> KEY = new
AttributeKey<String>(String.class,"myKey");
...
session.set(KEY,"myAttribute");
String attributeValue=session.get(KEY);
These 2 cases won't compile:
session.set(KEY,new Date());
Integer attributeValue=session.get(KEY);
This pattern would simplify the use of Attributes, because the programmer
don't have to care about the types and can concentrate on more improtant
things. In my humble opinion the Objekt keys should be removed at all, i
don't see the purpose for such unspecific keys.
