Struts2 Needs a new aliasInteceptor(thoughts?)

["matt.payne" <ma...@gmail.com>]

I have posted my thoughts about it 
http://blog.sutternow.com/2008/04/16/struts2-needs-a-new-aliasinterceptor
here . 

http://blog.sutternow.com/2008/04/16/struts2-needs-a-new-aliasinterceptor 

I will paste them below as well.

The original aliasInteceptor works fine for gluing together actions with
different parameter names that need to be clued together.  The limitation
with the existing solution is that properties for both name an alias need to
exist in the stack. 

The world keeps evolving though.  Developers make frequent use of richer
javascript widgets such as jQuery’s flexgrid or jqGrid. These widgets can
consume a specific JSON response and dish out their own unique set of named
parameters to the server side.  This presents a challenge when trying to
leverage existing back end code that works great, it just doesn’t match up
name wise to the parameters names coming in for a specific view.

Assume one has a some abstract PagingQueryAction(children just set
query/queryCount implementations) that can accept incoming parameters of:
   
    int pageSize = 10;  // results per page, default 10
    int currentPage;
    String filter;
    String sortorder = “asc”;
    String sortname = “”;

This works fine and dandy for some existing web views, but if one wanted to
make use of FlexGrid, they would create setters named.

    page 	3
    qtype 	name
    query 	
    rp 	15
    sortname 	iso
    sortorder 	asc

jqGrid has yet another set of name parameters that its submits.

Making new implementations of things because some UI widgets is hardcoded to
respond with a specfic set can be a PITA. 

If there existed an AliasInterceptor that would allow one to adapt to these
widget requirements people would have another solution at their disposal.

example of a mapping:

<!– usaged
  #{ ‘incomingName’ : ‘actionPropertyName’}
–>
    <package name=”json” extends=”inventoryDefault” namespace=”/json”>
            <action name=”summaryPagedJSON” class=”stateSummary”>
                 15 <!– change default here –>
                 #{ ‘query’ : ‘filter’, ‘rp’:'pageSize’,'page’:'currentPage’
}

                <result name=”success” type=”freemarker”>
                    json-pageSummary.ftl
                </result>
                <result name=”input” type=”freemarker”>
                    json-pageSummary.ftl
                </result>
            </action>
   
If one wanted to adapt the paging action for jqGrid, they’d simply need to
supply an alias parameter of:
  #{ ’searchString’ : ‘filter’,'page’:'currentPage’, ’sord’:’sortorder’,
’sidx’:’sortname’ }

(Note the freemarker template producing the JSON response may need to differ
slighty as well)

This proposed alias interceptor looks for the alias within
“invocationParameters” instead of the stack.
Perhaps we need to rename things.  The old AliasInterceptor is name
ChainingAliasInterceptor
and the new one is ParameterAliasInterceptor.
Or perhaps the alias functionality should just be built in to the existing
ParameterInterceptor.

snippet below
  @Override
    public String intercept(ActionInvocation invocation) throws Exception {

    ActionConfig config = invocation.getProxy().getConfig();
    ActionContext ac = invocation.getInvocationContext();

    // get the action’s parameters
    final Map configParameters = config.getParams();
    final Map invocationParameters = ac.getParameters();

    if (configParameters.containsKey(aliasesKey)) {

        String aliasExpression = (String) configParameters.get(aliasesKey);
        OgnlValueStack stack = (OgnlValueStack) ac.getValueStack();
        Object obj = stack.findValue(aliasExpression);

        if (obj != null && obj instanceof Map) {
        // override
        Map aliases = (Map) obj;
        Iterator itr = aliases.entrySet().iterator();
        while (itr.hasNext()) {
            Map.Entry entry = (Map.Entry) itr.next();
            String alias = entry.getKey().toString();
            String setterName = (String) entry.getValue();
       
            Object value = invocationParameters.get(alias);
            if (null != value) {
            stack.setValue(setterName, value);
           
            }
        }
        } else {
        log.debug(”invalid alias expression:” + aliasesKey);
        }
    }

    return invocation.invoke();
    }
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