/*
 * 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 java.io.Reader;
import java.io.Writer;
import java.io.IOException;
import javax.servlet.jsp.*;

/**
 * An encapsulation of the evaluation of the body of an action so it is
 * available to a tag handler.  BodyContent is a subclass of JspWriter.
 *
 * <p>
 * Note that the content of BodyContent is the result of evaluation, so
 * it will not contain actions and the like, but the result of their
 * invocation.
 * 
 * <p>
 * BodyContent has methods to convert its contents into
 * a String, to read its contents, and to clear the contents.
 *
 * <p>
 * The buffer size of a BodyContent object is unbounded.  A
 * BodyContent object cannot be in autoFlush mode.  It is not possible to
 * invoke flush on a BodyContent object, as there is no backing stream.
 *
 * <p>
 * Instances of BodyContent are created by invoking the pushBody and
 * popBody methods of the PageContext class.  A BodyContent is enclosed
 * within another JspWriter (maybe another BodyContent object) following
 * the structure of their associated actions.
 *
 * <p>
 * A BodyContent is made available to a BodyTag through a setBodyContent()
 * call.  The tag handler can use the object until after the call to
 * doEndTag().
 */

public abstract class BodyContent extends JspWriter {
    
    /**
     * Protected constructor.
     *
     * Unbounded buffer, no autoflushing.
     *
     * @param e the enclosing JspWriter
     */

    protected BodyContent(JspWriter e) {
	super(UNBOUNDED_BUFFER , false);
	this.enclosingWriter = e;
    }

    /**
     * Redefined flush() so it is not legal.
     *
     * <p>
     * It is not valid to flush a BodyContent because there is no backing
     * stream behind it.
     *
     * @throws IOException always thrown
     */

    public void flush() throws IOException {
	throw new IOException("Illegal to flush within a custom tag");
    }

    /**
     * Clear the body without throwing any exceptions.
     */
    
    public void clearBody() {
	try {
	    this.clear();
	} catch (IOException ex) {
	    // TODO -- clean this one up.
	    throw new Error("internal error!;");
	}
    }

    /**
     * Return the value of this BodyContent as a Reader.
     *
     * @return the value of this BodyContent as a Reader
     */
    public abstract Reader getReader();


    /**
     * Return the value of the BodyContent as a String.
     *
     * @return the value of the BodyContent as a String
     */
    public abstract String getString();
	

    /**
     * Write the contents of this BodyContent into a Writer.
     * Subclasses may optimize common invocation patterns.
     *
     * @param out The writer into which to place the contents of
     *     this body evaluation
     * @throws IOException if an I/O error occurred while writing the
     *     contents of this BodyContent to the given Writer
     */

    public abstract void writeOut(Writer out) throws IOException;


    /**
     * Get the enclosing JspWriter.
     *
     * @return the enclosing JspWriter passed at construction time
     */

    public JspWriter getEnclosingWriter() {
	return enclosingWriter;
    }


    // private fields

    private JspWriter enclosingWriter;
 }
