    001// Copyright 2006, 2007, 2008 The Apache Software Foundation
    002//
    003// Licensed under the Apache License, Version 2.0 (the "License");
    004// you may not use this file except in compliance with the License.
    005// You may obtain a copy of the License at
    006//
    007//     http://www.apache.org/licenses/LICENSE-2.0
    008//
    009// Unless required by applicable law or agreed to in writing, software
    010// distributed under the License is distributed on an "AS IS" BASIS,
    011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012// See the License for the specific language governing permissions and
    013// limitations under the License.
    014
    015package org.apache.tapestry5;
    016
    017import org.apache.tapestry5.dom.Document;
    018import org.apache.tapestry5.dom.Element;
    019import org.apache.tapestry5.dom.MarkupModel;
    020import org.apache.tapestry5.dom.Raw;
    021
    022import java.io.PrintWriter;
    023
    024/**
    025 * An interface used by objects, such as Tapestry components, that need to render themselves as some form of XML markup.
    026 * A markup writer maintains the idea of a current element. Attributes are added to the current element, and new text
    027 * and elements are placed inside the current element. In this way, the markup writer maintains a facade that XML markup
    028 * is generated as a stream, even though the implementation builds a kind of DOM tree. The DOM tree can be also be
    029 * manipulated. This solves a number of problems from Tapestry 4 (and earlier) where random access to the DOM was
    030 * desired and had to be simulated through complex buffering.
    031 */
    032public interface MarkupWriter
    033{
    034    /**
    035     * Begins a new element as a child of the current element. The new element becomes the current element. The new
    036     * Element is returned and can be directly manipulated (possibly at a later date). Optionally, attributes for the
    037     * new element can be specified directly.
    038     * <p/>
    039     *
    040     * @param name       the name of the element to create
    041     * @param attributes an even number of values, alternating names and values
    042     * @return the new DOM Element node
    043     * @see #attributes(Object[])
    044     */
    045    Element element(String name, Object... attributes);
    046
    047    /**
    048     * Ends the current element. The new current element will be the parent element. Returns the new current element
    049     * (which may be null when ending the root element for the document).
    050     */
    051
    052    Element end();
    053
    054    /**
    055     * Writes the text as a child of the current element.
    056     */
    057
    058    void write(String text);
    059
    060    /**
    061     * Writes a formatted string.
    062     */
    063    void writef(String format, Object... args);
    064
    065    /**
    066     * Writes <em>raw</em> text, text with existing markup that should be passed through the client without change. This
    067     * can be useful when the markup is read from an external source (a file or a database) and is simply to be
    068     * included.
    069     *
    070     * @param text
    071     * @see Raw
    072     */
    073    void writeRaw(String text);
    074
    075    /**
    076     * Adds an XML comment. The text should be just the comment content, the comment delimiters will be provided.
    077     * Note that, as of Tapestry 5.2., no extra whitespace is added (previous releases added a space around the text).
    078     */
    079    void comment(String text);
    080
    081
    082    /**
    083     * Adds parsed character content. This will be enclosed in a CDATA block if supported.  When not supported, this is
    084     * the same as {@link #write(String)}.
    085     *
    086     * @param content pre-parsed content
    087     */
    088    void cdata(String content);
    089
    090    /**
    091     * Adds a series of attributes and values. Null values are quietly skipped. If a name already has a value, then the
    092     * new value is <em>ignored</em>.
    093     */
    094    void attributes(Object... namesAndValues);
    095
    096    /**
    097     * Converts the collected markup into an markup stream (according to rules provided by the {@link Document}'s {@link
    098     * MarkupModel}). The markup stream is sent to the writer.
    099     */
    100    void toMarkup(PrintWriter writer);
    101
    102    /**
    103     * Returns the Document into which this writer creates elements or other nodes.
    104     */
    105    Document getDocument();
    106
    107    /**
    108     * Returns the currently active element.
    109     */
    110    Element getElement();
    111
    112    /**
    113     * Defines a namespace for the currently active element. The namespace URI will be mapped to the provided namespace
    114     * prefix within the Element.
    115     *
    116     * @param namespace       the namespace URI
    117     * @param namespacePrefix the prefix for elements and attributes associated with the namespace    (may be the empty
    118     *                        string for the default namespace)
    119     * @return the currently active element
    120     */
    121    Element defineNamespace(String namespace, String namespacePrefix);
    122
    123    /**
    124     * Starts an element within the given namespace. The correct namespace prefix will be identified and used. Must be
    125     * balanced by a call to {@link #end()}.
    126     *
    127     * @param namespace   URI containing the element
    128     * @param elementName name of the element within the namespace
    129     * @return the new Element
    130     */
    131    Element elementNS(String namespace, String elementName);
    132
    133    /**
    134     * Creates an attribute within the namespace for the current element.
    135     *
    136     * @param namespace      URI containing the element
    137     * @param attributeName  name of the attribute within the namespace
    138     * @param attributeValue the value for the attribute
    139     * @return the currently active element
    140     */
    141    Element attributeNS(String namespace, String attributeName, String attributeValue);
    142
    143    /**
    144     * Adds a markup writer listener that will be notified as elements are started and ended.
    145     */
    146    void addListener(MarkupWriterListener listener);
    147
    148    /**
    149     * Removes a previously added listener.
    150     */
    151    void removeListener(MarkupWriterListener listener);
    152}