Developing an Iterating Action
For a simple tag handler, iterative
evaluation of the body is simply done within the doTag(
)
method, as described earlier. A classic tag handler
doesn’t have this luxury. Instead, it must ask the
container to evaluate the action element’s body
repeatedly until some condition is true
. To do so,
it implements the
IterationTag
interface, which contains only one method: public
int doAfterBody( ) throws
JspException
, which is called by the container
after it has processed the action element’s body.
A tag handler that implements the IterationTag
interface is at first handled the same way as a tag handler
implementing the Tag
interface: the container
calls all property setter methods and the doStartTag(
)
method. Then things divert slightly, as illustrated in
Figure 21-5.
After the call to doStartTag( )
, the
doAfterBody( )
method may be called any number of
times before the doEndTag( )
method is called.
Let’s implement the same scaled-down version of the
<c:forEach>
action that I used to illustrate
iteration with a simple tag handler again but this time as a classic
tag handler. As before, the scaled down version supports only
Collection
data structures. The class tag handler
class is
shown in Example 21-9.
package com.ora.jsp.tags.xmp; import java.util.*; ...
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