Given your bent towards playing with "executable XML" here, you might want to take a serious look at the Jelly project as well.<snip> For the other usage, where people have trouble creating a finely-grained business API, there's a new Chain package in the Commons sandbox that can help. This package makes it easy to chain together arbitrary units of work, so that you can do things like create a "move" command by chaining a "copy" command to a "delete" command -- and still use "copy" or "delete" on their own. </snip>
Interesting. Sounds a lot like something I banged together the other day - a thing I unimaginatevly called the "steplib" as its a library for configuring steps to be executed.
Basically the units of work are classes that extend the Step class which defines a begin() & end() method that one overrides. Steps are organised into a tree, and can have children. If a steps begin() returns true the children are executed, and if a steps end() (executed after children are executed) returns true then the step is repeated. The step classes are stateless in a similar manner to actions and servlets, etc... and are configured in xml files which I read with digester the first time a particluar sequence is requested, and reuse for all subsequent requests for that sequence.
I did make a StepAction class that will execute a tree of steps (that subclass ActionStep heheh) for an action, though actually that was an afterthought and Im not using it much yet! The primary reason I built this thing was for use as a view rendering technology (Im allergic to JSP and prefer to decorate org.w3c.dom.Document trees (ahhh random access to my xhtml. Oh joy :->)...) as I wanted a better way to configure a sequence of more fine-grained DOM decorators.
Heres an example that does a listview table thingy:
<stamp id="stamp" mode="get" name="userRowStamp" remove="true"> <iterate exposeName="user" beanName="users" beanScope="request"> <log text="UserId:" name="user" property="userId" scope="request"/> <stamp id="userTable" mode="put" name="userRowStamp" remove="false"> <populate id="userTable" name="user"/> <rewrite id="userLink" forward="userEdit" paramId="userId" paramName="user" property="userId"/> <attribute id="userCheckbox" attribute="value" name="user" property="userId"/> <equals empty="true" name="user" property="roles"> <stamp id="roles_value" mode="get" remove="true"/> </equals> <equals not="true" empty="true" name="user" property="roles"> <stamp id="roles_br" mode="get" remove="true"/> </equals> <attribute id="stamp" attribute="id" remove="true" recurse="true"/> </stamp> </iterate> </stamp>
Of course for an action step sequence the steps could do such things as
"copy" or "delete".
http://jakarta.apache.org/commons/jelly/
It incorporates the notion of using an expression language very similar to JSTL 1.0 and JSTP 2.0, instead of the clunky XML things like the <logic:equals> and <logic:iterate> tags provide. The result is much more succinct scripts that can leverage all the power of the underlying expressions for conditionals, iterations, and so on.
Building a Struts action that invokes a Jelly script with a specified name is an exercize left for the reader (but it's really easy).
Craig
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