jakarta.servlet.jsp.tagext.SimpleTag Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates and others.
* All rights reserved.
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jakarta.servlet.jsp.tagext;
import jakarta.servlet.jsp.JspContext;
/**
* 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.
*
*
* @see SimpleTagSupport
* @since JSP 2.0
*/
public interface SimpleTag extends JspTag {
/**
* 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 jakarta.servlet.jsp.JspException If an error occurred while processing this tag.
* @throws jakarta.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 void doTag() throws jakarta.servlet.jsp.JspException, java.io.IOException;
/**
* 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
*/
public void setParent(JspTag parent);
/**
* Returns the parent of this tag, for collaboration purposes.
*
* @return the parent of this tag
*/
public JspTag getParent();
/**
* 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 void setJspContext(JspContext pc);
/**
* 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 void setJspBody(JspFragment jspBody);
}