Re: [commons-chain] Configuration of the ChainBase class

[Craig McClanahan]

Manfred Wolff wrote:
Moin.
Short description: We use commons-chain in a productive project for 
configuring strategies and filters. The user itsself should be able to 
customize the chains and brings the right order in chains (commands, 
filters ...). Some commands has dependencies to other commands so it 
might be the situation, that a command b can only be executed if a 
command a is still executed in the same chain. At runtime it is no 
problem to check such dependencies (b can look into the context if a 
has done his work). But because of the posibility of configuration the 
chains by customer it might be a good idea to do a check at the start 
of the app so configuration errors might not come into being at runtime.

For that I have subclassed the Command, the ChainBase etc. Unfortunaly 
in the class that have to be instanciated 
(org.apache.commons.chain.impl.ChainBase) is hard coded in the 
ConfigRuleSet class. So I have subclassed the RuleSet, the 
ConfigParser ... I think it make no sense to subclass all classes of a 
framework so I like to contribute a solution for generic instanciation 
support. For me it is enough to make the instanciaten class 
configurable (see my diff patchConfigRuleSet.txt). So I can subclass 
the ConfgParser and set the className attribute if needed. I have 
still some other solutions expanding the configuration file. All is 
possible by subclassing.

A new feature were good: It might be possible to configure chains in 
chains like that:

 <chain name="single">
     <command className="org.strutsit.chain.CommandForTestSomething"/>
     <command className="org.strutsit.chain.CommandForTestAnything"/>
 </chain>
 <chain name="depend">
     <chain refid=single"/>
     <command className="org.strutsit.chain.CommandForTestFalse"/>
     <command className="org.strutsit.chain.CommandForTestTrueDepend"/>
 </chain>
In the moment I have no knowledge how to configure a digester to do 
such things. If anybody has please contact me. I will implement the 
rest and contribute it too.

I just added the chainClass property as you proposed below, which means 
you can now set the default implementation class for all <chain> 
elements to be processed.  Note that, even before this change, you could 
use the "className" attribute on a <chain> element just like you could 
on a "command" element -- but I agree that having a default is nice.


Thanks a lot.
Manfred.
 

Craig
------------------------------------------------------------------------
RCS file: /home/cvspublic/jakarta-commons-sandbox/chain/src/java/org/apache/commons/chain/config/ConfigRuleSet.java,v
retrieving revision 1.5
diff -r1.5 ConfigRuleSet.java
67a68
 

   private String className= "org.apache.commons.chain.impl.ChainBase";
   

143a145,161
 

   
   /**
    * Return the classname that will use to instanciate chains. 
    * @return Returns the classeName.
    */
   public String getClassName() {
       return className;
   }

   
   /**
    * Sets the classname that will use to instanciate chains.
    * @param classeName The classeName to set.
    */
   public void setClassName(String classeName) {
       this.className = classeName;
   }
   

161c179
<                                  "org.apache.commons.chain.impl.ChainBase",
---
 

                                getClassName(),
   

 

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