javax.servlet.jsp.tagext.SimpleTag Maven / Gradle / Ivy

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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 javax.servlet.jsp.tagext;

import javax.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 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 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 void doTag()
        throws javax.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 );


}