javax.servlet.jsp.tagext
Interface SimpleTag
- JspTag
- SimpleTagSupport
public interface SimpleTag
Interface for defining Simple Tag Handlers.
Simple Tag Handlers differ from Classic Tag Handlers in that instead
of supporting
doStartTag() and
doEndTag(),
the
SimpleTag interface provides a simple
doTag() method, which is called once and only once for any
given tag invocation. All tag logic, iteration, body evaluations, etc.
are to be performed in this single method. Thus, simple tag handlers
have the equivalent power of
BodyTag, but with a much
simpler lifecycle and interface.
To support body content, the
setJspBody()
method is provided. The container invokes the
setJspBody()
method with a
JspFragment object encapsulating the body of
the tag. The tag handler implementation can call
invoke() on that fragment to evaluate the body as
many times as it needs.
A SimpleTag handler must have a public no-args constructor. Most
SimpleTag handlers should extend SimpleTagSupport.
Lifecycle
The following is a non-normative, brief overview of the
SimpleTag lifecycle. Refer to the JSP Specification for details.
- A new tag handler instance is created each time by the container
by calling the provided zero-args constructor. Unlike classic
tag handlers, simple tag handlers are never cached and reused by
the JSP container.
- The
setJspContext() and setParent()
methods are called by the container. The setParent()
method is only called if the element is nested within another tag
invocation. - The setters for each attribute defined for this tag are called
by the container.
- If a body exists, the
setJspBody() method is called
by the container to set the body of this tag, as a
JspFragment. If the action element is empty in
the page, this method is not called at all. - The
doTag() method is called by the container. All
tag logic, iteration, body evaluations, etc. occur in this
method. - The
doTag() method returns and all variables are
synchronized.
void | doTag()- Called by the container to invoke this tag.
|
JspTag | getParent()- Returns the parent of this tag, for collaboration purposes.
|
void | setJspBody(JspFragment jspBody)- Provides the body of this tag as a JspFragment object, able to be
invoked zero or more times by the tag handler.
|
void | setJspContext(JspContext pc)- Called by the container to provide this tag handler with
the
JspContext for this invocation.
|
void | setParent(JspTag parent)- Sets the parent of this tag, for collaboration purposes.
|
doTag
public void doTag()
throws JspException,
java.io.IOException Called by the container to invoke this tag.
The implementation of this method is provided by the tag library
developer, and handles all tag processing, body iteration, etc.
The JSP container will resynchronize any AT_BEGIN and AT_END
variables (defined by the associated tag file, TagExtraInfo, or TLD)
after the invocation of doTag().
JspException - If an error occurred
while processing this tag.
getParent
public JspTag getParent()
Returns the parent of this tag, for collaboration purposes.
setJspBody
public void setJspBody(JspFragment jspBody)
Provides the body of this tag as a JspFragment object, able to be
invoked zero or more times by the tag handler.
This method is invoked by the JSP page implementation
object prior to
doTag(). If the action element is
empty in the page, this method is not called at all.
jspBody - The fragment encapsulating the body of this tag.
setJspContext
public void setJspContext(JspContext pc)
Called by the container to provide this tag handler with
the JspContext for this invocation.
An implementation should save this value.
pc - the page context for this invocation
setParent
public void setParent(JspTag parent)
Sets the parent of this tag, for collaboration purposes.
The container invokes this method only if this tag invocation is
nested within another tag invocation.
parent - the tag that encloses this tag
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