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https://issues.apache.org/jira/browse/DIRMINA-874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13162793#comment-13162793
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Christian Schwarz commented on DIRMINA-874:
-------------------------------------------
Some hasty notes on the MINA 2 API..
<T> T getAttribute(String name);
- its not type safe
<T> T setAttribute(String name, T value);
- this is not possibe:
Number n = session.setAttribute(“key”,12)
Object removeAttribute(Object name);
- the type parameter is missing for the return type
- the name is not of type String
boolean containsAttribute(Object name);
- the name should be a String
Set<Object> getAttributeNames();
- the Set does not contain Strings as the user expects see #setAttribute(..)
Currently a attribute key-value pair can have 3 relevant states in a session
instance:
the key-value pair is absent
the key has a null value
the key has a non null value
The current Mina 3 API mixup case 1 and 2 in getAttribute(String) the user
don’t know which case happend if null is returned. Did i forget to set the
value or is it null? So if null values are supported, the user should know the
difference of null value and a value that is absent.
If the precondition is checked with containsAttribute(), who guaranees that no
datarace can occure ?
> Typesafe AttributeKeys
> ----------------------
>
> Key: DIRMINA-874
> URL: https://issues.apache.org/jira/browse/DIRMINA-874
> Project: MINA
> Issue Type: Improvement
> Components: Core
> Affects Versions: 3.0.0-M1
> Reporter: Christian Schwarz
>
> 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.
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