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SimpleTag.javaAPI DocApache Tomcat 6.0.146015Fri Jul 20 04:20:36 BST 2007javax.servlet.jsp.tagext

SimpleTag

public interface SimpleTag implements JspTag
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.

  1. 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.
  2. 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.
  3. The setters for each attribute defined for this tag are called by the container.
  4. 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.
  5. The doTag() method is called by the container. All tag logic, iteration, body evaluations, etc. occur in this method.
  6. The doTag() method returns and all variables are synchronized.
see
SimpleTagSupport
since
2.0

Fields Summary
Constructors Summary
Methods Summary
public voiddoTag()
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().

throws
javax.servlet.jsp.JspException If an error occurred while processing this tag.
throws
javax.servlet.jsp.SkipPageException If the page that (either directly or indirectly) invoked this tag is to cease evaluation. A Simple Tag Handler generated from a tag file must throw this exception if an invoked Classic Tag Handler returned SKIP_PAGE or if an invoked Simple Tag Handler threw SkipPageException or if an invoked Jsp Fragment threw a SkipPageException.
throws
java.io.IOException If there was an error writing to the output stream.

public JspTaggetParent()
Returns the parent of this tag, for collaboration purposes.

return
the parent of this tag

public voidsetJspBody(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.

param
jspBody The fragment encapsulating the body of this tag.

public voidsetJspContext(javax.servlet.jsp.JspContext pc)
Called by the container to provide this tag handler with the JspContext for this invocation. An implementation should save this value.

param
pc the page context for this invocation
see
Tag#setPageContext

public voidsetParent(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.

param
parent the tag that encloses this tag