[Webwork-devel] Sorting facilities expanded + example

[Rickard <ri...@xp...>]

Hey

I just put together a very simple example of a log4j console, which 
simply outputs the categories and the log levels that have been enabled 
for each category.

While doing so I had the need to use the "sort" tag to sort the list of 
categories according to their name. With the current CVS code I would 
have had to write a bean that provides a comparator that would do this 
sorting. While that would have worked, I wanted a more generic approach 
that one could use without having to do custom coding.

So, what I did was to extend the Sorter JavaBean to include a method 
getComparator(String anExpression) which creates a comparator that can 
compare two values that will be obtained by using the given WebWork 
expression on them.

For example, if I have a list of Person objects, and want to output them 
sorted by name (Person.getName()), then I simply have to call 
Sorter.getComparator("name") to get a comparator that can be used for 
the sort operation.

Thus, the category listing JSP code becomes (table header/footer removed):
<webwork:bean name="'webwork.util.Sorter'" id="sorter"/>
<webwork:action name="'log4j.categories'">
<form action="log4j.update.action" method="post">
<iterator:sort source="categories" comparator="@sorter/comparator('name')">
<webwork:iterator>
<tr>
<td><webwork:property value="name"/></td>
<td><input type=checkbox name="<webwork:property value="name"/>/debug" 
value="true" <webwork:if 
test="debugEnabled==true">checked</webwork:if>></td>
<td><input type=checkbox name="<webwork:property value="name"/>/info" 
value="true" <webwork:if test="infoEnabled==true">checked</webwork:if>></td>
</tr>
</webwork:iterator>
</iterator:sort>
</form>
</webwork:action>
--

The log4j.categories action simply provides the list of categories, and 
according to the JavaDoc the Category class has a getName() method, 
hence the "@sorter/comparator('name')" attribute in the sort tag. The 
expression can be any WW expression, but I think most cases will be of 
this rather simple variant.

Nice! :-)

Any thoughts on this? There is also a method in the Sorter to get the 
reverse comparator. I'm considering adding a boolean flag to the method 
for forward/backward ordering selection, which will allow dynamic 
selection of order.

/Rickard

ps. The above is not yet commited to CVS. Watch the dev list.

-- 
Rickard Öberg