Creating a Windowed Browser
Converting the code we've written to display a document in a window isn't difficult because that code was purposely written to store the output in an array of strings; I can display those strings in a Java window. In this example, I'll upgrade that code to a new program, browser.java, which will use XML for Java to display XML documents in a window.
Here's how it works; I start by parsing the document that the user wants to parse in the main method:
public static void main(String args[]) {
displayDocument(args[0]);
.
.
.Then I'll create a new window using the techniques we've seen in the previous chapter. Specifically, I'll create a new class named AppFrame, create an object of that class, and display it:
public static void main(String args[]) {
displayDocument(args[0]);
AppFrame f = new AppFrame(displayStrings, numberDisplayLines);
f.setSize(300, 500);
f.addWindowListener(new WindowAdapter() {public void
windowClosing(WindowEvent e) {System.exit(0);}});
f.show();
}
The AppFrame class is specially designed to display the output strings in the displayStrings array in a Java window. To do that, I pass that array and the number of lines to display to the AppFrame constructor, and store them in this new class:
class AppFrame extends Frame
{
String displayStrings[];
int numberDisplayLines;
public AppFrame(String[] strings, int number)
{
displayStrings = strings;
numberDisplayLines = number;
}
.
.
.
All that's left is to display the strings in the displayStrings array. When you display text in a Java window, you're responsible for positioning that text as you want it. To display multiline text, we'll need to know the height of a line of text in the window, and you can find that with the Java FontMetrics class's getHeight method.
Here's how I display the output text in the AppFrame window. I create a new Java Font object using Courier font, and install it in the Graphics object passed to the paint method. Then I find the height of each line of plain text:
public void paint(Graphics g)
{
Font font = new Font("Courier", Font.PLAIN, 12);
g.setFont(font);
FontMetrics fontmetrics = getFontMetrics(getFont());
int y = fontmetrics.getHeight();
.
.
.Finally, I loop over all lines of text, using the Java Graphics object's drawString method:
public void paint(Graphics g)
{
Font font = new Font("Courier", Font.PLAIN, 12);
g.setFont(font);
FontMetrics fontmetrics = getFontMetrics(getFont());
int y = fontmetrics.getHeight();
for(int index = 0; index < numberDisplayLines; index++){
y += fontmetrics.getHeight();
g.drawString(displayStrings[index], 5, y);
}
}
You can see the result in Figure 11.3. As you see in that figure, customer.xml is displayed in our windowed browser. The code for this example, browser.java, appears in Listing 11.3.
Figure 11.3. A graphical browser.
Code Listing 11.3. browser.java
import java.awt.*;
import java.awt.event.*;
import org.w3c.dom.*;
import org.apache.xerces.parsers.DOMParser;
public class browser
{
static String displayStrings[] = new String[1000];
static int numberDisplayLines = 0;
public static void displayDocument(String uri)
{
try {
DOMParser parser = new DOMParser();
parser.parse(uri);
Document document = parser.getDocument();
display(document, "");
} catch (Exception e) {
e.printStackTrace(System.err);
}
}
public static void display(Node node, String indent)
{
if (node == null) {
return;
}
int type = node.getNodeType();
switch (type) {
case Node.DOCUMENT_NODE: {
displayStrings[numberDisplayLines] = indent;
displayStrings[numberDisplayLines] +=
"<?xml version="1.0" encoding=""+
"UTF-8" + ""?>";
numberDisplayLines++;
display(((Document)node).getDocumentElement(), "");
break;
}
case Node.ELEMENT_NODE: {
displayStrings[numberDisplayLines] = indent;
displayStrings[numberDisplayLines] += "<";
displayStrings[numberDisplayLines] += node.getNodeName();
int length = (node.getAttributes() != null) ?
node.getAttributes().getLength() : 0;
Attr attrs[] = new Attr[length];
for (int loopIndex = 0; loopIndex < length; loopIndex++) {
attrs[loopIndex] =
(Attr)node.getAttributes().item(loopIndex);
}
for (int loopIndex = 0; loopIndex < attrs.length;
loopIndex++) {
Attr attr = attrs[loopIndex];
displayStrings[numberDisplayLines] += " ";
displayStrings[numberDisplayLines] += attr.getNodeName();
displayStrings[numberDisplayLines] += "="";
displayStrings[numberDisplayLines] +=
attr.getNodeValue();
displayStrings[numberDisplayLines] += """;
}
displayStrings[numberDisplayLines] += ">";
numberDisplayLines++;
NodeList childNodes = node.getChildNodes();
if (childNodes != null) {
length = childNodes.getLength();
indent += " ";
for (int loopIndex = 0; loopIndex < length; loopIndex++ ) {
display(childNodes.item(loopIndex), indent);
}
}
break;
}
case Node.CDATA_SECTION_NODE: {
displayStrings[numberDisplayLines] = indent;
displayStrings[numberDisplayLines] += "<![CDATA[";
displayStrings[numberDisplayLines] += node.getNodeValue();
displayStrings[numberDisplayLines] += "";
numberDisplayLines++;
break;
}
case Node.TEXT_NODE: {
displayStrings[numberDisplayLines] = indent;
String newText = node.getNodeValue().trim();
if(newText.indexOf("
") < 0 && newText.length() > 0) {
displayStrings[numberDisplayLines] += newText;
numberDisplayLines++;
}
break;
}
case Node.PROCESSING_INSTRUCTION_NODE: {
displayStrings[numberDisplayLines] = indent;
displayStrings[numberDisplayLines] += "<?";
displayStrings[numberDisplayLines] += node.getNodeName();
String text = node.getNodeValue();
if (text != null && text.length() > 0) {
displayStrings[numberDisplayLines] += text;
}
displayStrings[numberDisplayLines] += "?>";
numberDisplayLines++;
break;
}
}
if (type == Node.ELEMENT_NODE) {
displayStrings[numberDisplayLines] = indent.substring(0,
indent.length() - 4);
displayStrings[numberDisplayLines] += "</";
displayStrings[numberDisplayLines] += node.getNodeName();
displayStrings[numberDisplayLines] += ">";
numberDisplayLines++;
indent+= " ";
}
}
public static void main(String args[]) {
displayDocument(args[0]);
AppFrame f = new AppFrame(displayStrings, numberDisplayLines);
f.setSize(300, 500);
f.addWindowListener(new WindowAdapter() {public void
windowClosing(WindowEvent e) {System.exit(0);}});
f.show();
}
}
class AppFrame extends Frame
{
String displayStrings[];
int numberDisplayLines;
public AppFrame(String[] strings, int number)
{
displayStrings = strings;
numberDisplayLines = number;
}
public void paint(Graphics g)
{
Font font = new Font("Courier", Font.PLAIN, 12);
g.setFont(font);
FontMetrics fontmetrics = getFontMetrics(getFont());
int y = fontmetrics.getHeight();
for(int index = 0; index < numberDisplayLines; index++){
y += fontmetrics.getHeight();
g.drawString(displayStrings[index], 5, y);
}
}
}
|
Now that we're parsing and displaying XML documents in windows, there's no reason to restrict ourselves to displaying the text form of an XML document. Take a look at the next topic.