JavaServer Pages, 3rd Edition

Developing Cooperating Actions

It’s often necessary to develop custom actions so that they can be combined with other actions, letting them cooperate in some fashion. You have seen examples of this throughout this book. For instance, in Chapter 12, <sql:param> action elements are nested within the body of a <sql:query> action to set the values of placeholders in the SQL statement. Another example of cooperation is how the <c:forEach> action can use the query result produced by the <sql:query> action. In this section, we take a look at the cooperation techniques demonstrated by these two examples: explicit cooperation between a parent element and elements nested in its body and implicit cooperation through objects exposed as scoped variables.