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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

public class HTMLEditorKit

extends StyledEditorKit

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. It's 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 seperate 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.

See Also:

Serialized Form

Inner 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.

Inner classes inherited from class javax.swing.text.StyledEditorKit

StyledEditorKit.AlignmentAction, StyledEditorKit.BoldAction, StyledEditorKit.FontFamilyAction, StyledEditorKit.FontSizeAction, StyledEditorKit.ForegroundAction, StyledEditorKit.ItalicAction, StyledEditorKit.StyledTextAction, StyledEditorKit.UnderlineAction

Inner 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, insertContentAction, insertTabAction, nextWordAction, pageDownAction, pageUpAction, pasteAction, previousWordAction, readOnlyAction, selectAllAction, selectionBackwardAction, selectionBeginAction, selectionBeginLineAction, selectionBeginParagraphAction, selectionBeginWordAction, selectionDownAction, selectionEndAction, selectionEndLineAction, selectionEndParagraphAction, selectionEndWordAction, selectionForwardAction, selectionNextWordAction, selectionPreviousWordAction, selectionUpAction, selectLineAction, selectParagraphAction, selectWordAction, upAction, writableAction

Constructor Summary

HTMLEditorKit()
Constructs an HTMLEditorKit, creates a StyleContext, and loads the style sheet.

Method Summary

Object	clone() Create a copy of the editor kit.
Document	createDefaultDocument() Create an uninitialized text storage model that is appropriate for this type of editor.
protected void	createInputAttributes(Element element, MutableAttributeSet set) Copies the key/values in elements AttributeSet into set.
void	deinstall(JEditorPane c) Called when the kit is being removed from the JEditorPane.
Action[]	getActions() Fetches the command list for the editor.
String	getContentType() Get the MIME type of the data that this kit represents support for.
MutableAttributeSet	getInputAttributes() Gets the input attributes used for the styled editing actions.
protected HTMLEditorKit.Parser	getParser() Fetch the parser to use for reading html streams.
StyleSheet	getStyleSheet() Get the set of styles currently being used to render the html elements.
ViewFactory	getViewFactory() Fetch a factory that is suitable for producing views of any models that are produced by this kit.
void	insertHTML(HTMLDocument doc, int offset, String html, int popDepth, int pushDepth, HTML.Tag insertTag) Inserts HTML into an existing document.
void	install(JEditorPane c) Called when the kit is being installed into the a JEditorPane.
void	read(Reader in, Document doc, int pos) Inserts content from the given stream.
void	setStyleSheet(StyleSheet s) Set the set of styles to be used to render the various html elements.
void	write(Writer out, Document doc, int pos, int len) Write content from a document to the given stream in a format appropriate for this kind of content handler.

Methods inherited from class javax.swing.text.StyledEditorKit

getCharacterAttributeRun

Methods inherited from class javax.swing.text.DefaultEditorKit

createCaret, read, write

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_CSS

public static final String DEFAULT_CSS

Default Cascading Style Sheet file that sets up the tag views.

BOLD_ACTION

public static final String BOLD_ACTION

The bold action identifier

ITALIC_ACTION

public static final String ITALIC_ACTION

The italic action identifier

PARA_INDENT_LEFT

public static final String PARA_INDENT_LEFT

The paragraph left indent action identifier

PARA_INDENT_RIGHT

public static final String PARA_INDENT_RIGHT

The paragraph right indent action identifier

FONT_CHANGE_BIGGER

public static final String FONT_CHANGE_BIGGER

The font size increase to next value action identifier

FONT_CHANGE_SMALLER

public static final String FONT_CHANGE_SMALLER

The font size decrease to next value action identifier

COLOR_ACTION

public static final String COLOR_ACTION

The Color choice action identifier The color is passed as an argument

LOGICAL_STYLE_ACTION

public static final String LOGICAL_STYLE_ACTION

The logical style choice action identifier The logical style is passed in as an argument

IMG_ALIGN_TOP

public static final String IMG_ALIGN_TOP

Align images at the top.

IMG_ALIGN_MIDDLE

public static final String IMG_ALIGN_MIDDLE

Align images in the middle.

IMG_ALIGN_BOTTOM

public static final String IMG_ALIGN_BOTTOM

Align images at the bottom.

IMG_BORDER

public static final String IMG_BORDER

Align images at the border.

Constructor Detail

HTMLEditorKit

public HTMLEditorKit()

Constructs an HTMLEditorKit, creates a StyleContext, and loads the style sheet.

Method Detail

clone

public Object clone()

Create a copy of the editor kit. This allows an implementation to serve as a prototype for others, so that they can be quickly created.

Overrides:

clone in class StyledEditorKit

Returns:

the copy

getContentType

public String getContentType()

Get the MIME type of the data that this kit represents support for. This kit supports the type text/html.

Overrides:

getContentType in class DefaultEditorKit

Returns:

the type

getViewFactory

public ViewFactory getViewFactory()

Fetch a factory that is suitable for producing views of any models that are produced by this kit.

Overrides:

getViewFactory in class StyledEditorKit

Returns:

the factory

createDefaultDocument

public Document createDefaultDocument()

Create an uninitialized text storage model that is appropriate for this type of editor.

Overrides:

createDefaultDocument in class StyledEditorKit

Returns:

the model

read

public void read(Reader in,
                 Document doc,
                 int pos)
          throws IOException,
                 BadLocationException

Inserts content from the given stream. If doc is an instance of HTMLDocument, this will read html 3.2 text. Inserting html into a non-empty document must be inside the body Element, if you do not insert into the body an exception will be thrown. When inserting into a non-empty document all tags outside of the body (head, title) will be dropped.

Overrides:

read in class DefaultEditorKit

Parameters:

in - The stream to read from

doc - The destination for the insertion.

pos - The location in the document to place the content.

Throws:

IOException - on any I/O error

BadLocationException - if pos represents an invalid location within the document.

RuntimeException - (will eventually be a BadLocationException) if pos is invalid.

insertHTML

public void insertHTML(HTMLDocument doc,
                       int offset,
                       String html,
                       int popDepth,
                       int pushDepth,
                       HTML.Tag insertTag)
                throws BadLocationException,
                       IOException

Inserts HTML into an existing document.

Parameters:

doc - Document to insert into.

offset - offset to insert HTML at

popDepth - number of ElementSpec.EndTagType to generate before inserting.

pushDepth - number of ElementSpec.StartTagType with a direction of ElementSpec.JoinNextDirection that should be generated before inserting, but after the end tags have been generated.

insertTag - first tag to start inserting into document.

Throws:

RuntimeException - (will eventually be a BadLocationException) if pos is invalid.

write

public void write(Writer out,
                  Document doc,
                  int pos,
                  int len)
           throws IOException,
                  BadLocationException

Write content from a document to the given stream in a format appropriate for this kind of content handler.

Overrides:

write in class DefaultEditorKit

Parameters:

out - The stream to write to

doc - The source for the write.

pos - The location in the document to fetch the content.

len - The amount to write out.

Throws:

IOException - on any I/O error

BadLocationException - if pos represents an invalid location within the document.

install

public void install(JEditorPane c)

Called when the kit is being installed into the a JEditorPane.

Overrides:

install in class StyledEditorKit

Parameters:

c - the JEditorPane

deinstall

public void deinstall(JEditorPane c)

Called when the kit is being removed from the JEditorPane. This is used to unregister any listeners that were attached.

Overrides:

deinstall in class StyledEditorKit

Parameters:

c - the JEditorPane

setStyleSheet

public void setStyleSheet(StyleSheet s)

Set the set of styles to be used to render the various html elements. These styles are specified in terms of css specifications. Each document produced by the kit will have a copy of the sheet which it can add the document specific styles to. By default, the StyleSheet specified is shared by all HTMLEditorKit instances. This should be reimplemented to provide a finer granularity if desired.

getStyleSheet

public StyleSheet getStyleSheet()

Get the set of styles currently being used to render the html elements. By default the resource specified by DEFAULT_CSS gets loaded, and is shared by all HTMLEditorKit instances.

getActions

public Action[] getActions()

Fetches the command list for the editor. This is the list of commands supported by the superclass augmented by the collection of commands defined locally for style operations.

Overrides:

getActions in class StyledEditorKit

Returns:

the command list

createInputAttributes

protected void createInputAttributes(Element element,
                                     MutableAttributeSet set)

Copies the key/values in elements AttributeSet into set. This does not copy component, icon, or element names attributes. Subclasses may wish to refine what is and what isn't copied here. But be sure to first remove all the attributes that are in set.

This is called anytime the caret moves over a different location.

Overrides:

createInputAttributes in class StyledEditorKit

getInputAttributes

public MutableAttributeSet getInputAttributes()

Gets the input attributes used for the styled editing actions.

Overrides:

getInputAttributes in class StyledEditorKit

Returns:

the attribute set

getParser

protected HTMLEditorKit.Parser getParser()

Fetch the parser to use for reading html streams. This can be reimplemented to provide a different parser. The default implementation is loaded dynamically to avoid the overhead of loading the default parser if it's not used. The default parser is the HotJava parser using an html 3.2 dtd.