javax.swing.text.html
Class HTMLEditorKit

java.lang.Object
  |
  +--javax.swing.text.EditorKit
        |
        +--javax.swing.text.DefaultEditorKit
              |
              +--javax.swing.text.StyledEditorKit
                    |
                    +--javax.swing.text.html.HTMLEditorKit
All Implemented Interfaces:
Accessible, Cloneable, Serializable
public class HTMLEditorKit
extends StyledEditorKit
implements Accessible

The Swing JEditorPane text component supports different kinds of content via a plug-in mechanism called an EditorKit. Because HTML is a very popular format of content, some support is provided by default. The default support is provided by this class, which supports HTML version 3.2 (with some extensions), and is migrating toward version 4.0. The <applet> tag is not supported, but some support is provided for the <object> tag.

There are several goals of the HTML EditorKit provided, that have an effect upon the way that HTML is modeled. These have influenced its design in a substantial way.

Support editing
It might seem fairly obvious that a plug-in for JEditorPane should provide editing support, but that fact has several design considerations. There are a substantial number of HTML documents that don't properly conform to an HTML specification. These must be normalized somewhat into a correct form if one is to edit them. Additionally, users don't like to be presented with an excessive amount of structure editing, so using traditional text editing gestures is preferred over using the HTML structure exactly as defined in the HTML document.

The modeling of HTML is provided by the class HTMLDocument. Its documention describes the details of how the HTML is modeled. The editing support leverages heavily off of the text package.

Extendable/Scalable
To maximize the usefulness of this kit, a great deal of effort has gone into making it extendable. These are some of the features.
  1. The parser is replacable. The default parser is the Hot Java parser which is DTD based. A different DTD can be used, or an entirely different parser can be used. To change the parser, reimplement the getParser method. The default parser is dynamically loaded when first asked for, so the class files will never be loaded if an alternative parser is used. The default parser is in a separate package called parser below this package.
  2. The parser drives the ParserCallback, which is provided by HTMLDocument. To change the callback, subclass HTMLDocument and reimplement the createDefaultDocument method to return document that produces a different reader. The reader controls how the document is structured. Although the Document provides HTML support by default, there is nothing preventing support of non-HTML tags that result in alternative element structures.
  3. The default view of the models are provided as a hierarchy of View implementations, so one can easily customize how a particular element is displayed or add capabilities for new kinds of elements by providing new View implementations. The default set of views are provided by the HTMLFactory class. This can be easily changed by subclassing or replacing the HTMLFactory and reimplementing the getViewFactory method to return the alternative factory.
  4. The View implementations work primarily off of CSS attributes, which are kept in the views. This makes it possible to have multiple views mapped over the same model that appear substantially different. This can be especially useful for printing. For most HTML attributes, the HTML attributes are converted to CSS attributes for display. This helps make the View implementations more general purpose

Asynchronous Loading
Larger documents involve a lot of parsing and take some time to load. By default, this kit produces documents that will be loaded asynchronously if loaded using JEditorPane.setPage. This is controlled by a property on the document. The method createDefaultDocument can be overriden to change this. The batching of work is done by the HTMLDocument.HTMLReader class. The actual work is done by the DefaultStyledDocument and AbstractDocument classes in the text package.

Customization from current LAF
HTML provides a well known set of features without exactly specifying the display characteristics. Swing has a theme mechanism for its look-and-feel implementations. It is desirable for the look-and-feel to feed display characteristics into the HTML views. An user with poor vision for example would want high contrast and larger than typical fonts.

The support for this is provided by the StyleSheet class. The presentation of the HTML can be heavily influenced by the setting of the StyleSheet property on the EditorKit.

Not lossy
An EditorKit has the ability to be read and save documents. It is generally the most pleasing to users if there is no loss of data between the two operation. The policy of the HTMLEditorKit will be to store things not recognized or not necessarily visible so they can be subsequently written out. The model of the HTML document should therefore contain all information discovered while reading the document. This is constrained in some ways by the need to support editing (i.e. incorrect documents sometimes must be normalized). The guiding principle is that information shouldn't be lost, but some might be synthesized to produce a more correct model or it might be rearranged.

 

Nested Class Summary

static class HTMLEditorKit.HTMLFactory
    A factory to build views for HTML.
static class HTMLEditorKit.HTMLTextAction
    An abstract Action providing some convenience methods that may be useful in inserting HTML into an existing document.
static class HTMLEditorKit.InsertHTMLTextAction
    InsertHTMLTextAction can be used to insert an arbitrary string of HTML into an existing HTML document.
static class HTMLEditorKit.LinkController
    Class to watch the associated component and fire hyperlink events on it when appropriate.
static class HTMLEditorKit.Parser
    Interface to be supported by the parser.
static class HTMLEditorKit.ParserCallback
    The result of parsing drives these callback methods.
 
Nested classes inherited from class javax.swing.text.StyledEditorKit
StyledEditorKit.AlignmentAction, StyledEditorKit.BoldAction, StyledEditorKit.FontFamilyAction, StyledEditorKit.FontSizeAction, StyledEditorKit.ForegroundAction, StyledEditorKit.ItalicAction, StyledEditorKit.UnderlineAction
 
Nested classes inherited from class javax.swing.text.DefaultEditorKit
DefaultEditorKit.BeepAction, DefaultEditorKit.CopyAction, DefaultEditorKit.CutAction, DefaultEditorKit.DefaultKeyTypedAction, DefaultEditorKit.InsertBreakAction, DefaultEditorKit.InsertContentAction, DefaultEditorKit.InsertTabAction, DefaultEditorKit.PasteAction
 

 

Field Summary

static String BOLD_ACTION
    The bold action identifier
static String COLOR_ACTION
    The Color choice action identifier The color is passed as an argument
static String DEFAULT_CSS
    Default Cascading Style Sheet file that sets up the tag views.
static String FONT_CHANGE_BIGGER
    The font size increase to next value action identifier
static String FONT_CHANGE_SMALLER
    The font size decrease to next value action identifier
static String IMG_ALIGN_BOTTOM
    Align images at the bottom.
static String IMG_ALIGN_MIDDLE
    Align images in the middle.
static String IMG_ALIGN_TOP
    Align images at the top.
static String IMG_BORDER
    Align images at the border.
static String ITALIC_ACTION
    The italic action identifier
static String LOGICAL_STYLE_ACTION
    The logical style choice action identifier The logical style is passed in as an argument
static String PARA_INDENT_LEFT
    The paragraph left indent action identifier
static String PARA_INDENT_RIGHT
    The paragraph right indent action identifier
 
Fields inherited from class javax.swing.text.DefaultEditorKit
backwardAction, beepAction, beginAction, beginLineAction, beginParagraphAction, beginWordAction, copyAction, cutAction, defaultKeyTypedAction, deleteNextCharAction, deletePrevCharAction, downAction, endAction, endLineAction, EndOfLineStringProperty, endParagraphAction, endWordAction, forwardAction, insertBreakAction,