Editor plugin modules are available in Confluence 2.5 and later versions

Editor plugin modules allow you to implement Wysiwyg editors for editing Confluence pages.

<atlassian-plugin key="com.atlassian.confluence.extra.tinymceplugin" name="TinyMCE Editor Plugin">
    <plugin-info>
        <description>TinyMCE Editor Plugin for Confluence</description>
        <version>${project.version}</version>
        <vendor name="Atlassian" url="http://www.atlassian.com"/>
    </plugin-info>
    ...
    <editor name="tinymceeditor" class="com.atlassian.confluence.extra.tinymceplugin.TinyMceEditor" key="tinymceeditor">
        <description>TinyMCE Editor</description>
    </editor>
    ...
</atlassian-plugin>

package com.atlassian.confluence.plugin.editor;

/**
 * This interface allows Wysiwyg editors to be plugged in to Confluence.
 */
public interface Editor
{
    /**
     * Returns javascript functions to allow thw wiki-textarea.vm to interface with the editor.
     *
     * The Javascript returned must define the functions:
     *
     * onShowEditor() -- this is called just after the DIV containing the editor is made visible. It is a hook where you
     *      can place any special code needed at this point.
     * onHideEditor() -- this is called just before the DIV containing the editor is hidden. It is a hook where you
     *      can place any special code needed at this point.
     * setEditorValue(newValue) -- put the text in newValue into the editor. This is called when the editor needs new
     *      content -- it is *not* called to set the initial content. That should be done either by providing the
     *      editor with the content as part of the initial HTML, or by calling javascript from editorOnLoad().
     * allowModeChange() -- return true if the editor is in a state where changes from rich text to markup and vice versa are allowed.
     * getEditorHTML() -- return the current HTML contents of the editor. This *must* return a JavaScript string,
     *      not a JavaObject wrapping a java.lang.String!
     * editorOnLoad() -- called in the page's onLoad handler, place any initialization needed at this point here.
     * editorHasContentChanged() -- return true if the contents of the editor has been modified by the user since
     *      the last time editorResetContentChanged().
     * editorResetContentChanged() -- called to reset the contents change indicator
     *
     * These methods won't be called when the editor is not visible.
     *
     * The javascript must be surrounded by a <script> element.
     * @return a String containing a velocity template
     */
    String getJavascriptTemplate();

    /**
     * Returns the div contents to display the editor itself.
     * @return a String containing a velocity template
     */
    String getDivContentsTemplate();

    /**
     * Return true if the user agent string indicates a browser which is supported by this editor
     * @param userAgent
     * @return true if this editor is supported
     */
    boolean supportedUserAgent(String userAgent);

    /**
     * Perform any necessary escaping of the HTML rendered by Confluence. The AbstractPreviewPageAction.getWysiwygContent()
     *      method uses this method to escape the rendered HTML.
     */
    String escapeHtml(String html);

    /**
     * Return a string of CSS which will be appended to the standard stylesheet if it is requested from /styles/wysiwyg-action
     *
     * Note that it is up to the editor implementation to retrieve this stylesheet and apply it to the editor contents --
     * the page containing the editor is styled with the normal stylesheet.
     */
    String getEditorSpecificCss();
}