Overview

OGNL is the Object Graph Navigation Language - see http://www.ognl.org for the full documentation of OGNL. In this document we will only show a few examples of OGNL features that co-exist with Webwork. To review basic concepts, refer to OGNL Basics.

Webwork uses a standard naming context to evaluate OGNL expressions. The top level object dealing with OGNL is a map (usually referred as a context map). OGNL has a concept of a root object (in webwork terms, this is the OGNLValueStack). Along with the root, other objects are placed in the context map (referred as in the context) including your session/application/request/attr maps. These objects have nothing to do with the root, they just exist along side it in the context map. So, to access these objects, the # is used telling ognl not to look in the root object, but within the rest of the context

                     |--request
                     |
                     |--application
                     |
       context map---|--OgnlValueStack(root)
                     |
                     |--session
                     |
                     |--attr
                     |
                     |--parameters

Note that their are other objects in the context map, I'm just referring to a few for this example. Now, your actions instances are placed in the OGNLValueStack so you can refer to your bean properties without the #.

<ww: property value="myBean.myProperty"/>

For sessions,request, and the rest that lie in the context map:

ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject);

<ww:property value="#session.mySessionPropKey"/> or
<ww:property value="#session['mySessionPropKey']"/> or
<ww:property value="#attr.mySessionPropKey"/>

Collections (Maps, Lists, Sets)

Dealing with collections(maps, lists, and sets) in webwork comes often, so here are a few examples using the select tag:
Syntax for list: {e1,e2,e3}. This creates a List containing the String "name1", "name2" and "name3". It also selects "name2" as the default value. Notice the use of the Alt Syntax to provide the literal "name2".

<ww:select label="label" name="name" list="{'name1','name2','name3'}" value="%{'name2'}" />

Syntax for map: #{key1:value1,key2:value2}. This creates a map that maps the string "foo" to the string "foovalue" and "bar" to the string "barvalue":

<ww:select label="label" name="name" list="#{'foo':'foovalue', 'bar':'barvalue'}" />

You may need to determine if an element exists in a collection. You can accomplish this with the operations in and not in

<ww:if test="'foo' in {'foo','bar'}">
   muhahaha
</ww:if>
<ww:else>
   boo
</ww:else>

<ww:if test="'foo' not in {'foo','bar'}">
   muhahaha
</ww:if>
<ww:else>
   boo
</ww:else>

To select a subset of a collection (called projection), you can use a wildcard within the collection.

• ? - All elements matching the selection logic
• ^ - Only the first element matching the selection logic
• $ - Only the last element matching the selection logic

To obtain a subset of just male relatives from the object person:

person.relatives.{? #this.gender == 'male'}

Lambda Expressions

OGNL supports basic lamba expression syntax enabling you to write simple functions. For example:

For all you math majors who didn't think you would ever see this one again.
Fibonacci: if n==0 return 0; elseif n==1 return 1; else return fib(n-2)+fib(n-1);
fib(0) = 0
fib(1) = 1
fib(11) = 89

<ww:property value="#fib =:[#this==0 ? 0 : #this==1 ? 1 : #fib(#this-2)+#fib(#this-1)], #fib(11)" />