- /*
- * The Apache Software License, Version 1.1
- *
- * Copyright (c) 1999 The Apache Software Foundation. All rights
- * reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. The end-user documentation included with the redistribution, if
- * any, must include the following acknowlegement:
- * "This product includes software developed by the
- * Apache Software Foundation (http://www.apache.org/)."
- * Alternately, this acknowlegement may appear in the software itself,
- * if and wherever such third-party acknowlegements normally appear.
- *
- * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
- * Foundation" must not be used to endorse or promote products derived
- * from this software without prior written permission. For written
- * permission, please contact apache@apache.org.
- *
- * 5. Products derived from this software may not be called "Apache"
- * nor may "Apache" appear in their names without prior written
- * permission of the Apache Group.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- * ====================================================================
- *
- * This software consists of voluntary contributions made by many
- * individuals on behalf of the Apache Software Foundation. For more
- * information on the Apache Software Foundation, please see
- * <http://www.apache.org/>.
- *
- */
-
- package javax.servlet.jsp.tagext;
-
- import javax.servlet.jsp.*;
-
-
- /**
- * The interface of a simple tag handler that does not want to manipulate its body.
- * The Tag interface defines the basic protocol between a Tag handler and
- * JSP page implementation class. It defines the life cycle and the
- * methods to be invoked at start and end tag.
- *
- * <p><B>Properties</B>
- *
- * <p>
- * The Tag interface specifies the setter and getter methods for the core
- * pageContext and parent properties.
- *
- * <p> The JSP page implementation object invokes setPageContext and
- * setParent, in that order, before invoking doStartTag() or doEndTag().
- *
- * <p><B>Methods</B>
- *
- * <p>
- * There are two main actions: doStartTag and doEndTag. Once all
- * appropriate properties have been initialized, the doStartTag and
- * doEndTag methods can be invoked on the tag handler. Between these
- * invocations, the tag handler is assumed to hold a state that must
- * be preserved. After the doEndTag invocation, the tag handler is
- * available for further invocations (and it is expected to have
- * retained its properties).
- *
- * <p><B>Lifecycle</B>
- * <p> Lifecycle details are described by the transition diagram below,
- * with the following comments:
- * <ul>
- * <li> [1] This transition is intended to be for releasing long-term data.
- * no guarantees are assumed on whether any properties have been retained
- * or not.
- * <li> [2] This transition happens if and only if the tag ends normally
- * without raising an exception
- * <li> [3] Note that since there are no guarantees on the state of the
- * properties, a tag handler that had some optional properties set can only be
- * reused if those properties are set to a new (known) value. This means
- * that tag handlers can only be reused within the same "AttSet" (set of
- * attributes that have been set).
- * <li> Check the TryCatchFinally interface for additional details related
- * to exception handling and resource management.
- * </ul>
- *
- * <IMG src="doc-files/TagProtocol.gif"/>
- *
- * <p> Once all invocations on the tag handler
- * are completed, the release method is invoked on it. Once a release
- * method is invoked <em>all</em> properties, including parent and
- * pageContext, are assumed to have been reset to an unspecified value.
- * The page compiler guarantees that release() will be invoked on the Tag
- * handler before the handler is released to the GC.
- *
- * <p><B>Empty and Non-Empty Action</B>
- * <p> If the TagLibraryDescriptor file indicates that the action must
- * always have an empty action, by an <body-content> entry of "empty",
- * then the doStartTag() method must return SKIP_BODY.
- *
- * Otherwise, the doStartTag() method may return SKIP_BODY or
- * EVAL_BODY_INCLUDE.
- *
- * <p>
- * If SKIP_BODY is returned the body, if present, is not evaluated.
- *
- * <p>
- * If EVAL_BODY_INCLUDE is returned, the body is evaluated and
- * "passed through" to the current out.
- */
-
- public interface Tag {
-
- /**
- * Skip body evaluation.
- * Valid return value for doStartTag and doAfterBody.
- */
-
- public final static int SKIP_BODY = 0;
-
- /**
- * Evaluate body into existing out stream.
- * Valid return value for doStartTag.
- */
-
- public final static int EVAL_BODY_INCLUDE = 1;
-
- /**
- * Skip the rest of the page.
- * Valid return value for doEndTag.
- */
-
- public final static int SKIP_PAGE = 5;
-
- /**
- * Continue evaluating the page.
- * Valid return value for doEndTag().
- */
-
- public final static int EVAL_PAGE = 6;
-
- // Setters for Tag handler data
-
-
- /**
- * Set the current page context.
- * This method is invoked by the JSP page implementation object
- * prior to doStartTag().
- * <p>
- * This value is *not* reset by doEndTag() and must be explicitly reset
- * by a page implementation if it changes between calls to doStartTag().
- *
- * @param pc The page context for this tag handler.
- */
-
- void setPageContext(PageContext pc);
-
-
- /**
- * Set the parent (closest enclosing tag handler) of this tag handler.
- * Invoked by the JSP page implementation object prior to doStartTag().
- * <p>
- * This value is *not* reset by doEndTag() and must be explicitly reset
- * by a page implementation.
- *
- * @param t The parent tag, or null.
- */
-
-
- void setParent(Tag t);
-
-
- /**
- * Get the parent (closest enclosing tag handler) for this tag handler.
- *
- * <p>
- * The getParent() method can be used to navigate the nested tag
- * handler structure at runtime for cooperation among custom actions;
- * for example, the findAncestorWithClass() method in TagSupport
- * provides a convenient way of doing this.
- *
- * <p>
- * The current version of the specification only provides one formal
- * way of indicating the observable type of a tag handler: its
- * tag handler implementation class, described in the tag-class
- * subelement of the tag element. This is extended in an
- * informal manner by allowing the tag library author to
- * indicate in the description subelement an observable type.
- * The type should be a subtype of the tag handler implementation
- * class or void.
- * This addititional constraint can be exploited by a
- * specialized container that knows about that specific tag library,
- * as in the case of the JSP standard tag library.
- *
- * @returns the current parent, or null if none.
- * @seealso TagSupport.findAncestorWithClass().
- */
-
- Tag getParent();
-
-
- // Actions for basic start/end processing.
-
-
- /**
- * Process the start tag for this instance.
- * This method is invoked by the JSP page implementation object.
- *
- * <p>
- * The doStartTag method assumes that the properties pageContext and
- * parent have been set. It also assumes that any properties exposed as
- * attributes have been set too. When this method is invoked, the body
- * has not yet been evaluated.
- *
- * <p>
- * This method returns Tag.EVAL_BODY_INCLUDE or
- * BodyTag.EVAL_BODY_BUFFERED to indicate
- * that the body of the action should be evaluated or SKIP_BODY to
- * indicate otherwise.
- *
- * <p>
- * When a Tag returns EVAL_BODY_INCLUDE the result of evaluating
- * the body (if any) is included into the current "out" JspWriter as it
- * happens and then doEndTag() is invoked.
- *
- * <p>
- * BodyTag.EVAL_BODY_BUFFERED is only valid if the tag handler
- * implements BodyTag.
- *
- * <p>
- * The JSP container will resynchronize
- * any variable values that are indicated as so in TagExtraInfo after the
- * invocation of doStartTag().
- *
- * @returns EVAL_BODY_INCLUDE if the tag wants to process body, SKIP_BODY if it
- * does not want to process it.
- * @throws JspException.
- * @see BodyTag
- */
-
- int doStartTag() throws JspException;
-
-
- /**
- * Process the end tag for this instance.
- * This method is invoked by the JSP page implementation object
- * on all Tag handlers.
- *
- * <p>
- * This method will be called after returning from doStartTag. The
- * body of the action may or not have been evaluated, depending on
- * the return value of doStartTag.
- *
- * <p>
- * If this method returns EVAL_PAGE, the rest of the page continues
- * to be evaluated. If this method returns SKIP_PAGE, the rest of
- * the page is not evaluated and the request is completed. If this
- * request was forwarded or included from another page (or Servlet),
- * only the current page evaluation is completed.
- *
- * <p>
- * The JSP container will resynchronize
- * any variable values that are indicated as so in TagExtraInfo after the
- * invocation of doEndTag().
- *
- * @returns indication of whether to continue evaluating the JSP page.
- * @throws JspException.
- */
-
- int doEndTag() throws JspException;
-
- /**
- * Called on a Tag handler to release state.
- * The page compiler guarantees that JSP page implementation
- * objects will invoke this method on all tag handlers,
- * but there may be multiple invocations on doStartTag and doEndTag in between.
- */
-
- void release();
-
- }