Module java.desktop
Package javax.swing.text

Class AbstractDocument

  • All Implemented Interfaces:
    Serializable, Document
    Direct Known Subclasses:
    DefaultStyledDocument, PlainDocument

    public abstract class AbstractDocument
extends Object
implements Document, Serializable
    An implementation of the document interface to serve as a basis for implementing various kinds of documents. At this level there is very little policy, so there is a corresponding increase in difficulty of use.

    This class implements a locking mechanism for the document. It allows multiple readers or one writer, and writers must wait until all observers of the document have been notified of a previous change before beginning another mutation to the document. The read lock is acquired and released using the render method. A write lock is acquired by the methods that mutate the document, and are held for the duration of the method call. Notification is done on the thread that produced the mutation, and the thread has full read access to the document for the duration of the notification, but other readers are kept out until the notification has finished. The notification is a beans event notification which does not allow any further mutations until all listeners have been notified.

    Any models subclassed from this class and used in conjunction with a text component that has a look and feel implementation that is derived from BasicTextUI may be safely updated asynchronously, because all access to the View hierarchy is serialized by BasicTextUI if the document is of type AbstractDocument. The locking assumes that an independent thread will access the View hierarchy only from the DocumentListener methods, and that there will be only one event thread active at a time.

    If concurrency support is desired, there are the following additional implications. The code path for any DocumentListener implementation and any UndoListener implementation must be threadsafe, and not access the component lock if trying to be safe from deadlocks. The repaint and revalidate methods on JComponent are safe.

    AbstractDocument models an implied break at the end of the document. Among other things this allows you to position the caret after the last character. As a result of this, getLength returns one less than the length of the Content. If you create your own Content, be sure and initialize it to have an additional character. Refer to StringContent and GapContent for examples of this. Another implication of this is that Elements that model the implied end character will have an endOffset == (getLength() + 1). For example, in DefaultStyledDocument getParagraphElement(getLength()).getEndOffset() == getLength() + 1 .

    Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.

    See Also:
    Serialized Form

    • Field Detail

      • listenerList

        protected EventListenerList listenerList
        The event listener list for the document.

      • ParagraphElementName

        public static final String ParagraphElementName
        Name of elements used to represent paragraphs
        See Also:
        Constant Field Values

      • ContentElementName

        public static final String ContentElementName
        Name of elements used to represent content
        See Also:
        Constant Field Values

      • SectionElementName

        public static final String SectionElementName
        Name of elements used to hold sections (lines/paragraphs).
        See Also:
        Constant Field Values

      • BidiElementName

        public static final String BidiElementName
        Name of elements used to hold a unidirectional run
        See Also:
        Constant Field Values

      • ElementNameAttribute

        public static final String ElementNameAttribute
        Name of the attribute used to specify element names.
        See Also:
        Constant Field Values

    • Constructor Detail

      • AbstractDocument

        protected AbstractDocument​(AbstractDocument.Content data)
        Constructs a new AbstractDocument, wrapped around some specified content storage mechanism.
        Parameters:
        data - the content

    • Method Detail

      • fireInsertUpdate

        protected void fireInsertUpdate​(DocumentEvent e)
        Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created using the parameters passed into the fire method.
        Parameters:
        e - the event
        See Also:
        EventListenerList

      • fireChangedUpdate

        protected void fireChangedUpdate​(DocumentEvent e)
        Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created using the parameters passed into the fire method.
        Parameters:
        e - the event
        See Also:
        EventListenerList

      • fireRemoveUpdate

        protected void fireRemoveUpdate​(DocumentEvent e)
        Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created using the parameters passed into the fire method.
        Parameters:
        e - the event
        See Also:
        EventListenerList

      • fireUndoableEditUpdate

        protected void fireUndoableEditUpdate​(UndoableEditEvent e)
        Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created using the parameters passed into the fire method.
        Parameters:
        e - the event
        See Also:
        EventListenerList

      • getListeners

        public <T extends EventListener> T[] getListeners​(Class<T> listenerType)
        Returns an array of all the objects currently registered as FooListeners upon this document. FooListeners are registered using the addFooListener method.

        You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a document d for its document listeners with the following code: 

        DocumentListener[] mls = (DocumentListener[])(d.getListeners(DocumentListener.class));
        If no such listeners exist, this method returns an empty array.
        Type Parameters:
        T - the listener type
        Parameters:
        listenerType - the type of listeners requested
        Returns:
        an array of all objects registered as FooListeners on this component, or an empty array if no such listeners have been added
        Throws:
        ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener
        Since:
        1.3
        See Also:
        getDocumentListeners(), getUndoableEditListeners()

      • getAsynchronousLoadPriority

        public int getAsynchronousLoadPriority​()
        Gets the asynchronous loading priority. If less than zero, the document should not be loaded asynchronously.
        Returns:
        the asynchronous loading priority, or -1 if the document should not be loaded asynchronously

      • setAsynchronousLoadPriority

        public void setAsynchronousLoadPriority​(int p)
        Sets the asynchronous loading priority.
        Parameters:
        p - the new asynchronous loading priority; a value less than zero indicates that the document should not be loaded asynchronously

      • setDocumentFilter

        public void setDocumentFilter​(DocumentFilter filter)
        Sets the DocumentFilter. The DocumentFilter is passed insert and remove to conditionally allow inserting/deleting of the text. A null value indicates that no filtering will occur.
        Parameters:
        filter - the DocumentFilter used to constrain text
        Since:
        1.4
        See Also:
        getDocumentFilter()

      • render

        public void render​(Runnable r)
        This allows the model to be safely rendered in the presence of currency, if the model supports being updated asynchronously. The given runnable will be executed in a way that allows it to safely read the model with no changes while the runnable is being executed. The runnable itself may not make any mutations.

        This is implemented to acquire a read lock for the duration of the runnables execution. There may be multiple runnables executing at the same time, and all writers will be blocked while there are active rendering runnables. If the runnable throws an exception, its lock will be safely released. There is no protection against a runnable that never exits, which will effectively leave the document locked for it's lifetime.

        If the given runnable attempts to make any mutations in this implementation, a deadlock will occur. There is no tracking of individual rendering threads to enable detecting this situation, but a subclass could incur the overhead of tracking them and throwing an error.

        This method is thread safe, although most Swing methods are not. Please see Concurrency in Swing for more information.

        Specified by:
        render in interface Document
        Parameters:
        r - the renderer to execute

      • getLength

        public int getLength​()
        Returns the length of the data. This is the number of characters of content that represents the users data.
        Specified by:
        getLength in interface Document
        Returns:
        the length >= 0
        See Also:
        Document.getLength()

      • getProperty

        public final Object getProperty​(Object key)
        A convenience method for looking up a property value. It is equivalent to: 
         getDocumentProperties().get(key);
        Specified by:
        getProperty in interface Document
        Parameters:
        key - the non-null property key
        Returns:
        the value of this property or null
        See Also:
        getDocumentProperties()

      • putProperty

        public final void putProperty​(Object key,
                              Object value)
        A convenience method for storing up a property value. It is equivalent to: 
         getDocumentProperties().put(key, value);
        If value is null this method will remove the property.
        Specified by:
        putProperty in interface Document
        Parameters:
        key - the non-null key
        value - the property value
        See Also:
        getDocumentProperties()

      • remove

        public void remove​(int offs,
                   int len)
            throws BadLocationException
        Removes some content from the document. Removing content causes a write lock to be held while the actual changes are taking place. Observers are notified of the change on the thread that called this method.

        This method is thread safe, although most Swing methods are not. Please see Concurrency in Swing for more information.

        Specified by:
        remove in interface Document
        Parameters:
        offs - the starting offset >= 0
        len - the number of characters to remove >= 0
        Throws:
        BadLocationException - the given remove position is not a valid position within the document
        See Also:
        Document.remove(int, int)

      • replace

        public void replace​(int offset,
                    int length,
                    String text,
                    AttributeSet attrs)
             throws BadLocationException
        Deletes the region of text from offset to offset + length, and replaces it with text. It is up to the implementation as to how this is implemented, some implementations may treat this as two distinct operations: a remove followed by an insert, others may treat the replace as one atomic operation.
        Parameters:
        offset - index of child element
        length - length of text to delete, may be 0 indicating don't delete anything
        text - text to insert, null indicates no text to insert
        attrs - AttributeSet indicating attributes of inserted text, null is legal, and typically treated as an empty attributeset, but exact interpretation is left to the subclass
        Throws:
        BadLocationException - the given position is not a valid position within the document
        Since:
        1.4

      • getText

        public String getText​(int offset,
                      int length)
               throws BadLocationException
        Gets a sequence of text from the document.
        Specified by:
        getText in interface Document
        Parameters:
        offset - the starting offset >= 0
        length - the number of characters to retrieve >= 0
        Returns:
        the text
        Throws:
        BadLocationException - the range given includes a position that is not a valid position within the document
        See Also:
        Document.getText(int, int)

      • getText

        public void getText​(int offset,
                    int length,
                    Segment txt)
             throws BadLocationException
        Fetches the text contained within the given portion of the document.

        If the partialReturn property on the txt parameter is false, the data returned in the Segment will be the entire length requested and may or may not be a copy depending upon how the data was stored. If the partialReturn property is true, only the amount of text that can be returned without creating a copy is returned. Using partial returns will give better performance for situations where large parts of the document are being scanned. The following is an example of using the partial return to access the entire document: 

           int nleft = doc.getDocumentLength();
   Segment text = new Segment();
   int offs = 0;
   text.setPartialReturn(true);
   while (nleft > 0) {
       doc.getText(offs, nleft, text);
       // do something with text
       nleft -= text.count;
       offs += text.count;
   }
        Specified by:
        getText in interface Document
        Parameters:
        offset - the starting offset >= 0
        length - the number of characters to retrieve >= 0
        txt - the Segment object to retrieve the text into
        Throws:
        BadLocationException - the range given includes a position that is not a valid position within the document

      • getStartPosition

        public final Position getStartPosition​()
        Returns a position that represents the start of the document. The position returned can be counted on to track change and stay located at the beginning of the document.
        Specified by:
        getStartPosition in interface Document
        Returns:
        the position

      • getEndPosition

        public final Position getEndPosition​()
        Returns a position that represents the end of the document. The position returned can be counted on to track change and stay located at the end of the document.
        Specified by:
        getEndPosition in interface Document
        Returns:
        the position

      • getRootElements

        public Element[] getRootElements​()
        Gets all root elements defined. Typically, there will only be one so the default implementation is to return the default root element.
        Specified by:
        getRootElements in interface Document
        Returns:
        the root element

      • getDefaultRootElement

        public abstract Element getDefaultRootElement​()
        Returns the root element that views should be based upon unless some other mechanism for assigning views to element structures is provided.
        Specified by:
        getDefaultRootElement in interface Document
        Returns:
        the root element
        See Also:
        Document.getDefaultRootElement()

      • getBidiRootElement

        public Element getBidiRootElement​()
        Returns the root element of the bidirectional structure for this document. Its children represent character runs with a given Unicode bidi level.
        Returns:
        the root element of the bidirectional structure for this document

      • getParagraphElement

        public abstract Element getParagraphElement​(int pos)
        Get the paragraph element containing the given position. Sub-classes must define for themselves what exactly constitutes a paragraph. They should keep in mind however that a paragraph should at least be the unit of text over which to run the Unicode bidirectional algorithm.
        Parameters:
        pos - the starting offset >= 0
        Returns:
        the element

      • getAttributeContext

        protected final AbstractDocument.AttributeContext getAttributeContext​()
        Fetches the context for managing attributes. This method effectively establishes the strategy used for compressing AttributeSet information.
        Returns:
        the context

      • insertUpdate

        protected void insertUpdate​(AbstractDocument.DefaultDocumentEvent chng,
                            AttributeSet attr)
        Updates document structure as a result of text insertion. This will happen within a write lock. If a subclass of this class reimplements this method, it should delegate to the superclass as well.
        Parameters:
        chng - a description of the change
        attr - the attributes for the change

      • removeUpdate

        protected void removeUpdate​(AbstractDocument.DefaultDocumentEvent chng)
        Updates any document structure as a result of text removal. This method is called before the text is actually removed from the Content. This will happen within a write lock. If a subclass of this class reimplements this method, it should delegate to the superclass as well.
        Parameters:
        chng - a description of the change

      • postRemoveUpdate

        protected void postRemoveUpdate​(AbstractDocument.DefaultDocumentEvent chng)
        Updates any document structure as a result of text removal. This method is called after the text has been removed from the Content. This will happen within a write lock. If a subclass of this class reimplements this method, it should delegate to the superclass as well.
        Parameters:
        chng - a description of the change

      • dump

        public void dump​(PrintStream out)
        Gives a diagnostic dump.
        Parameters:
        out - the output stream

      • getContent

        protected final AbstractDocument.Content getContent​()
        Gets the content for the document.
        Returns:
        the content

      • createLeafElement

        protected Element createLeafElement​(Element parent,
                                    AttributeSet a,
                                    int p0,
                                    int p1)
        Creates a document leaf element. Hook through which elements are created to represent the document structure. Because this implementation keeps structure and content separate, elements grow automatically when content is extended so splits of existing elements follow. The document itself gets to decide how to generate elements to give flexibility in the type of elements used.
        Parameters:
        parent - the parent element
        a - the attributes for the element
        p0 - the beginning of the range >= 0
        p1 - the end of the range >= p0
        Returns:
        the new element

      • createBranchElement

        protected Element createBranchElement​(Element parent,
                                      AttributeSet a)
        Creates a document branch element, that can contain other elements.
        Parameters:
        parent - the parent element
        a - the attributes
        Returns:
        the element

      • getCurrentWriter

        protected final Thread getCurrentWriter​()
        Fetches the current writing thread if there is one. This can be used to distinguish whether a method is being called as part of an existing modification or if a lock needs to be acquired and a new transaction started.
        Returns:
        the thread actively modifying the document or null if there are no modifications in progress

      • writeLock

        protected final void writeLock​()
        Acquires a lock to begin mutating the document this lock protects. There can be no writing, notification of changes, or reading going on in order to gain the lock. Additionally a thread is allowed to gain more than one writeLock, as long as it doesn't attempt to gain additional writeLocks from within document notification. Attempting to gain a writeLock from within a DocumentListener notification will result in an IllegalStateException. The ability to obtain more than one writeLock per thread allows subclasses to gain a writeLock, perform a number of operations, then release the lock.

        Calls to writeLock must be balanced with calls to writeUnlock, else the Document will be left in a locked state so that no reading or writing can be done.

        Throws:
        IllegalStateException - thrown on illegal lock attempt. If the document is implemented properly, this can only happen if a document listener attempts to mutate the document. This situation violates the bean event model where order of delivery is not guaranteed and all listeners should be notified before further mutations are allowed.

      • writeUnlock

        protected final void writeUnlock​()
        Releases a write lock previously obtained via writeLock. After decrementing the lock count if there are no outstanding locks this will allow a new writer, or readers.
        See Also:
        writeLock()

      • readLock

        public final void readLock​()
        Acquires a lock to begin reading some state from the document. There can be multiple readers at the same time. Writing blocks the readers until notification of the change to the listeners has been completed. This method should be used very carefully to avoid unintended compromise of the document. It should always be balanced with a readUnlock.
        See Also:
        readUnlock()

      • readUnlock

        public final void readUnlock​()
        Does a read unlock. This signals that one of the readers is done. If there are no more readers then writing can begin again. This should be balanced with a readLock, and should occur in a finally statement so that the balance is guaranteed. The following is an example. 
        
     readLock();
     try {
         // do something
     } finally {
         readUnlock();
     }
        See Also:
        readLock()