/*
 * 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 java.io.IOException;
import java.io.Reader;
import java.io.Writer;

import javax.servlet.jsp.JspWriter;

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.

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.

BodyContent has methods to convert its contents into a String, to read its
contents, and to clear the contents.

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.

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.

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().
/**
 * 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.
Params:
e – 
           the enclosing 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.

It is not valid to flush a BodyContent because there is no backing stream
behind it.
Throws:
IOException – 
            always thrown/**
     * 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
     */
    @Override
    public void flush() throws IOException {
        throw new IOException("Illegal to flush within a custom tag");
    }

    
Clear the body without throwing any exceptions.
/**
     * 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.
Returns:
the value of this BodyContent as a Reader/**
     * 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.
Returns:
the value of the BodyContent as a String/**
     * 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.
Params:
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/**
     * 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.
Returns:
the enclosing JspWriter passed at construction time/**
     * Get the enclosing JspWriter.
     *
     * @return the enclosing JspWriter passed at construction time
     */
    public JspWriter getEnclosingWriter() {
        return enclosingWriter;
    }

    // private fields

    private final JspWriter enclosingWriter;
}