Well, Iguess if it is going to make your life, or someone elses life
easier, it should be in there. Since you can always refactor, I guess you
use it while things are simple enough, and pull it out when they get too
complex. I just saw how ATG Dynamo attempted to do everything with
Configuration files and the Swing UI and they were saying how
siteadminstrators could add code without needing an engineer. People
believed it. But basically what they wrote wasa scripting layer in XML
that was a propriatary scripting language. Personally, I would prefer
Java Code generation to XML scripting.
Adam Young
Lead Programmer
RTZ Associates
510-986-6700
-----Original Message-----
From: Oleg V Alexeev <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Date: Fri, 20 Jul 2001 02:32:20 +0400
Subject: Re[2]: Build Command service on base of FactoryService
> Hello Adam,
>
> Thursday, July 19, 2001, 7:05:59 PM, you wrote:
>
> AY> The main reason I am concerned is that I saw this happen in ATG:
> AY> Processing logic moves from Java code to XML. The problem is that
> it
> AY> becomes much harder to isolate a particular Bug. Unit testing is
> AY> allmost impossible. My suggestion is that if you want to make it
> easy
> AY> to do List/Add/Delete functionality, make helper classes to do it.
> While
> AY> I've been using JBoss for my Object-Relational mapping, many people
> have
> AY> written classes that wrap a table/query etc.
>
> May be you are right. But imagine common situation - you are needs to
> list rows from DB table by the JSP page. So with struts you are place
> call to the database or to the DAO to the Action and forward to the
> page. And such operation (write simple call to the JDBC source to
> execute query and retrieve values) you are needs to perform for every
> simple query. I think that such processing logic is more than standart
> and make it part of code is superfluous.
> For example - experienced developer write processor code to process
> calls to the JDBC data source and ordinal developer with help of DBA
> write command tag and place it to the appropriate action. After that
> he can place tags to retrieve data from objects and not write complex
> code with calls to the exteranl datasource.
>
> AY> The design pattern that best reflects what you are trying to do is
> the
> AY> template method (Design Patterns, Go4, p325). You want to separate
> the
> AY> flow logic from what happens at each step of the way.
>
> AY> void teplateMethod(){
> AY> step1();
> AY> step2();
> AY> if (success(step3()){
> AY> step4();
> AY> }
> AY> }
>
> AY> Pretty easy to do in Java, and keeps the code clean.
>
> No problem. Commands can be used from java code. Developer can find
> all needed Processors and Commands and perform call to the processor
> for the any count of Commands. He can change logic of applications but
> he don't need to change standart operations under application data.
>
> AY> One of the key issues you have to deal with in coding is where does
> AY> coding leave off and configuration begin. I tend to err on the
> side of
> AY> codeing: Abstract methods that must be defined to use the class
> AY> correctly. At the other extreme is the Interpreter pattern.
>
> I don't want to code all Processors and Commands, no. I want to build
> framework to use Processors and Commands, specified by class name.
> Everybody can write its own Processor or Command and use it with
> CommandService. I think JDBC Processor is not single choice to perform
> processing. There are - RowSet Processor, XML Processor, Castor
> Processor, etc.
>
> AY> One thing I really like about struts is the ability to have one
> place
> AY> that you define your Components.
>
> AY> The way my make file works, there is not really a big benefit to
> doing
> AY> something late bound that does not force a recompile since I end up
> AY> doing a complete redeploy for any changes. (JBoss with embedded
> AY> Tomcat). This pushes the focus to building unit tests that run
> before
> AY> the deploy stage. Any logic in the XML file makes this more
> difficult.
> AY> Granted, it is just another way to develop.
>
> Yes, I agree with you... It is difficalt to perform unit tests with
> it.
>
> AY> Adam
>
>
> AY> Oleg V Alexeev wrote:
>
> >>Hello Adam,
> >>
> >>Wednesday, July 18, 2001, 8:51:58 PM, you wrote:
> >>
> >>AY> This sounds like the pipeline/chain setup from ATG. My one
> concern is
> >>AY> that you will end up with convoluted processing logic in the xml.
> >>
> >>Main idea is to describe commands in XML and let to manipulate such
> >>blocks without code recompilation.
> >>
> >>AY> Iwould recomend that this type of processing stay in the java
> code. I
> >>AY> also would be a little wary of the SQL code migrating into the
> XML.
> >>
> >>Why? It can be useful for small projects with insert/update/delete
> >>logic only.
> >>
> >>AY> If this is related to the idea of chaining actions we talked
> about
> >>AY> before, it may be better to provide an API inside of the Action
> object
> >>AY> Forward to another action. Although What I would like to see is
> the
> >>AY> ability of a Action object to take a collection of Form's. While
> I
> >>AY> typically would use two (The previopus pages form and the next
> pages
> >>AY> form) I could see needing another.
> >>
> >>
> >>AY> Oleg V Alexeev wrote:
> >>
> >>>>Hello struts-dev,
> >>>>
> >>>> This day I start to build new service for ServiceManager -
> >>>> CommandService. It would be based on FactoryService (early
> published
> >>>> as BeanFactory).
> >>>>
> >>>> FactoryService (as BeanFactory) build on base of Abstract Factory
> >>>> pattern. So its idea is to generate beans and store it to the some
> >>>> context. Now I found such approach as limited.
> >>>>
> >>>> CommandService idea is based on Command pattern. There are two
> >>>> entity types on playground - Command and Processor. Processor's
> >>>> missing is to perform Command and prepare predefined count of
> result
> >>>> objects. Every action can contain list of calls to the Processors
> >>>> with appropriate Commands. The most simple way to pass results
> from
> >>>> on Porcessor to another is to perfom processing and store result
> in
> >>>> some context (request, session, etc.). More flexible way is to
> >>>> write nested calls to the Processors with appropriate Commands.
> And
> >>>> generally all this stuff (set of Processors and
> >>>> Commands) can be used to build some kind of scripting in
> >>>> struts-config.xml with BSF framework.
> >>>>
> >>>> Example of service manager config in struts-config -
> >>>>
> >>>> <service-manager>
> >>>> <process-registrations>
> >>>> <process-registration name="preprocess"/>
> >>>> </process-registrations>
> >>>> <service-registrations>
> >>>> <service-registration
> >>>> name="command"
> >>>> type="org.apache.struts.service.command.CommandService"
> >>>> useDigester="true">
> >>>> <command-service>
> >>>> <processors>
> >>>> <processor name="jdbcUpdate" type="some.package.Class">
> >>>> <result
> >>>> name="totalUpdated"
> >>>> type="java.lang.Integer"/>
> >>>> </processor>
> >>>> </processors>
> >>>> <commands>
> >>>> <command
> >>>> name="createUser"
> >>>> command="insert into rb.user( name ) values ( ? )">
> >>>> <processors>
> >>>> <processor name="jdbcUpdate"/>
> >>>> </processors>
> >>>> <parameter
> >>>> name="method"
> >>>> type="java.lang.String"
> >>>> value="preparedStatement"/>
> >>>> <parameter
> >>>> name="userName"
> >>>> type="java.lang.String"/>
> >>>> </command>
> >>>> </commands>
> >>>> </command-service>
> >>>> </service-registrations>
> >>>> </service-manager>
> >>>>
> >>>> <action-mappings>
> >>>> <action path="/user/insert"
> >>>> type="some.package.Action"
> >>>> name="userForm"
> >>>> input="/WEB-INF/jsp/userEdit.jsp">
> >>>> <perform-command name="createUser"/>
> >>>> <forward name="success" path="/WEB-INF/jsp/userList.jsp"/>
> >>>> </action>
> >>>> </action-mappings>
> >>>>
> >>>>
> >>>>
> >>
> >>
> >>
> >>
>
>
>
>
> --
> Best regards,
> Oleg mailto:[EMAIL PROTECTED]
>
