Xml syntax highlighting in Swing JTextPane

First we extend JTextPane:

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public class XmlTextPane extends JTextPane {

private static final long serialVersionUID = 6270183148379328084L;

public XmlTextPane() {

// Set editor kit
this.setEditorKitForContentType("text/xml", new XmlEditorKit());
this.setContentType("text/xml");
}

}
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Next we define a custom EditorKit:

{code}
public class XmlEditorKit extends StyledEditorKit {

private static final long serialVersionUID = 2969169649596107757L;
private ViewFactory xmlViewFactory;

public XmlEditorKit() {
xmlViewFactory = new XmlViewFactory();
}

@Override
public ViewFactory getViewFactory() {
return xmlViewFactory;
}

@Override
public String getContentType() {
return "text/xml";
}
}
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The EditorKit needs a ViewFactory:

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public class XmlViewFactory extends Object implements ViewFactory {

/**
* @see javax.swing.text.ViewFactory#create(javax.swing.text.Element)
*/
public View create(Element element) {

return new XmlView(element);
}

}
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Finally we create the syntax highlighting view:

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package nl.boplicity.swing.text;

import java.awt.Color;
import java.awt.Graphics;
import java.util.HashMap;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.Element;
import javax.swing.text.PlainDocument;
import javax.swing.text.PlainView;
import javax.swing.text.Segment;
import javax.swing.text.Utilities;

/**
* Thanks: http://groups.google.com/group/de.comp.lang.java/msg/2bbeb016abad270
*
* IMPORTANT NOTE: regex should contain 1 group.
*
* Using PlainView here because we don't want line wrapping to occur.
*
* @author kees
* @date 13-jan-2006
*
*/
public class XmlView extends PlainView {

private static HashMap<Pattern, Color> patternColors;
private static String TAG_PATTERN = "(</?[a-z]*)\\s?>?";
private static String TAG_END_PATTERN = "(/>)";
private static String TAG_ATTRIBUTE_PATTERN = "\\s(\\w*)\\=";
private static String TAG_ATTRIBUTE_VALUE = "[a-z-]*\\=(\"[^\"]*\")";
private static String TAG_COMMENT = "(<!--.*-->)";
private static String TAG_CDATA_START = "(\\<!\\[CDATA\\[).*";
private static String TAG_CDATA_END = ".*(]]>)";

static {
// NOTE: the order is important!
patternColors = new HashMap<Pattern, Color>();
patternColors.put(Pattern.compile(TAG_CDATA_START), new Color(128, 128, 128));
patternColors.put(Pattern.compile(TAG_CDATA_END), new Color(128, 128, 128));
patternColors
.put(Pattern.compile(TAG_PATTERN), new Color(63, 127, 127));
patternColors.put(Pattern.compile(TAG_ATTRIBUTE_PATTERN), new Color(
127, 0, 127));
patternColors.put(Pattern.compile(TAG_END_PATTERN), new Color(63, 127,
127));
patternColors.put(Pattern.compile(TAG_ATTRIBUTE_VALUE), new Color(42,
0, 255));
patternColors.put(Pattern.compile(TAG_COMMENT), new Color(63, 95, 191));
}

public XmlView(Element element) {

super(element);

// Set tabsize to 4 (instead of the default 8)
getDocument().putProperty(PlainDocument.tabSizeAttribute, 4);
}

@Override
protected int drawUnselectedText(Graphics graphics, int x, int y, int p0,
int p1) throws BadLocationException {

Document doc = getDocument();
String text = doc.getText(p0, p1 - p0);

Segment segment = getLineBuffer();

SortedMap<Integer, Integer> startMap = new TreeMap<Integer, Integer>();
SortedMap<Integer, Color> colorMap = new TreeMap<Integer, Color>();

// Match all regexes on this snippet, store positions
for (Map.Entry<Pattern, Color> entry : patternColors.entrySet()) {

Matcher matcher = entry.getKey().matcher(text);

while (matcher.find()) {
startMap.put(matcher.start(1), matcher.end());
colorMap.put(matcher.start(1), entry.getValue());
}
}

// TODO: check the map for overlapping parts

int i = 0;

// Colour the parts
for (Map.Entry<Integer, Integer> entry : startMap.entrySet()) {
int start = entry.getKey();
int end = entry.getValue();

if (i < start) {
graphics.setColor(Color.black);
doc.getText(p0 + i, start - i, segment);
x = Utilities.drawTabbedText(segment, x, y, graphics, this, i);
}

graphics.setColor(colorMap.get(start));
i = end;
doc.getText(p0 + start, i - start, segment);
x = Utilities.drawTabbedText(segment, x, y, graphics, this, start);
}

// Paint possible remaining text black
if (i < text.length()) {
graphics.setColor(Color.black);
doc.getText(p0 + i, text.length() - i, segment);
x = Utilities.drawTabbedText(segment, x, y, graphics, this, i);
}

return x;
}

}
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