Re: [sca-j] Can we use method-level Intent/PolicySet annotations in thejava component implementation class to express implementation QoSrequirements?

[David Booz <booz@us.ibm.com>]

Honestly, I don't feel strongly either way. We have to be careful with transactions because they can create tight coupling between services. Different transaction behaviors for each method doesn't strike me as a central focus for SOA style interfaces. Such an interface would limit the possible alternative interfaces which could connect to it, thus making it a fine grained interface and not appropriate for a SOA. That said, I recognize that there are varying degrees of interpretation on what's appropriate in SOA interfaces.

EJB3 is a very good fine grained model which supports different use cases than SCA.

Are there other opinions?

Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:booz@us.ibm.com

Raymond Feng---10/20/2009 06:02:17 PM---Hi, For example, I would like to set up the implementation class with

From:	Raymond Feng/Burlingame/IBM@IBMUS
To:	sca-j@lists.oasis-open.org
Date:	10/20/2009 06:02 PM
Subject:	[sca-j] Can we use method-level Intent/PolicySet annotations in the java component implementation class to express implementation QoS requirements?

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Hi, 

For example, I would like to set up the implementation class with transaction requirements using method-level annotations to declare implementation intents/policySets for a java component. 

@Service(AccountService.class) 
public class AccountServiceImpl { 

        @ManagedSharedTransaction 
        public void transfer(String account1, String account2, float amount) { 
                } 

        @NoManagedTransaction 
        public float getBalance(String account) { 
        } 
} 

We can do similar things in EJB3. 

But the Java CAA spec has the following statement: 

854 Intent annotations MUST NOT be applied to the following: 
855 • A method of a service implementation class, except for a setter method that is either 
856 annotated with @Reference or introspected as an SCA reference according to the rules in 
857 the appropriate Component Implementation specification 

This will make the sample above invalid. 

I don't think we should be forced to require the same intent for the whole class as it is quite common that different operations have different QoS requirements. 

We could argue that this can be done at interface methods. But in this case, the transaction requirements are decided by the implementation instead of the interface.   

What do you think? 

Thanks, 
Raymond

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Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer 
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400, Foster City, CA 94404, USA
E-mail: rfeng@us.ibm.com, Notes: Raymond Feng/Burlingame/IBM, Tel: 650-645-8117, T/L: 367-8117
Apache Tuscany: http://tuscany.apache.org
Co-author of Tuscany In Action: http://www.manning.com/laws

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