Java Server Pages

Processing the Action Body

As you can see, it’s easy to develop a tag handler that doesn’t need to do anything with the action element’s body. For a tag handler that does need to process the body, however, just a few more methods are needed. They are defined by the BodyTag interface, which extends the Tag interface.

The action element’s body has many possible uses. It can be used for input values spanning multiple lines; the SQL custom actions introduced in Chapter 9, use the body this way. The SQL statement is often large, so it’s better to let the page author write it in the action body instead of forcing it to fit on one line, which is a requirement for an attribute value. The body can also contain nested actions that rely on the enclosing action in some way. The <ora:sqlTransaction> action, also from Chapter 9, provides the nested SQL actions with the DataSource object they use to communicate with the database, and ensures that the SQL statements in all actions are treated as one transaction that either fails or succeeds.

A third example is an action that processes the body content in one way or another before it’s added to the response. Chapter 12, contains an example of an action that processes its XML body using the XSL stylesheet specified as an attribute. Later in this section we look at an action that replaces characters that have special meanings in HTML with the corresponding HTML character entities.

As with the Tag interface, there’s a BodyTagSupport class that ...