The Command service

The Command service is based on Apache's commons-chain and allows to encapsulate methods to execute as a Command objects

A Command framework Application can create own Catalog of Commands, configuring org.exoplatform.services.command.impl.CommonsXMLConfigurationPlugin as following:

<component>
    <key>org.exoplatform.services.command.impl.CommandService</key>
    <type>org.exoplatform.services.command.impl.CommandService</type>
    <component-plugins>    
      <component-plugin> 
          <name>config.catalog</name>
          <set-method>addPlugin</set-method>
          <type>org.exoplatform.services.command.impl.CommonsXMLConfigurationPlugin</type>
          <init-params>
            <value-param>
              <name>config-file</name>
              <value>conf/test-commands.xml</value>
            </value-param>
          </init-params>    
      </component-plugin>
    </component-plugins>      
  </component>

Where test-commands.xml is commons-chain standard chain definition xml like:

<catalog>
  <command   name="addNode"
        className="org.exoplatform.frameworks.jcr.command.core.AddNodeCommand"/>
  <command   name="save"
        className="org.exoplatform.frameworks.jcr.command.core.SaveCommand"/>
  <command   name="setProperty"
        className="org.exoplatform.frameworks.jcr.command.core.SetPropertyCommand"/>
</catalog>

CommandService's CommonsXMLConfigurationPlugin uses Apache commons-chain's CatalogFactory instance of which is a singleton for the relevant ClassLoader. For applications that use a thread context class loader (such as web applications running inside a servet container), static getInstance() method will return a separate instance for each application, even if this class is loaded from a shared parent class loader.

Multiple Configuration and Multiple Catalogs:

There is one default Catalog (exposed as element catalog without "name" attribute, as in example above) and it is possible to configure named Catalogs (like catalog name="my-name"). Each Catalog's configuration can be added in different CommonsXMLConfigurationPlugin entries.

For instance, you can have a plugin configuration like:

........
          <type>org.exoplatform.services.command.impl.CommonsXMLConfigurationPlugin</type>
          <init-params>
            <value-param>
              <name>config-file</name>
              <value>conf/test-commands1.xml</value>
            </value-param>
          </init-params>    
        ........

with

<catalog>
  <command   name="save"
        className="org.exoplatform.frameworks.jcr.command.core.SaveCommand"/>
</catalog>

inside conf/test-commands1.xml file and

........
          <type>org.exoplatform.services.command.impl.CommonsXMLConfigurationPlugin</type>
          <init-params>
            <value-param>
              <name>config-file</name>
              <value>conf/test-commands2.xml</value>
            </value-param>
          </init-params>    
     ........

with

<catalog>
  <command   name="addNode"
        className="org.exoplatform.frameworks.jcr.command.core.AddNodeCommand"/>
</catalog>

inside conf/test-commands2.xml file and at the end you will have both save and addNode commands accessible in the default catalog (the same is valid for named catalogs of course)

last modified by Oleksandr Tkachenko on 27/03/2008 at 15:15

The Command service

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