corejava第10版

2019-05-22 19:31:49 +08:00
1 parent 2021c3c227
commit 6165543dd3
@@ -0,0 +1,155 @@
+package xpath;
+
+import java.awt.*;
+import java.awt.event.*;
+import java.io.*;
+import java.nio.file.*;
+import java.util.*;
+import javax.swing.*;
+import javax.swing.border.*;
+import javax.xml.namespace.*;
+import javax.xml.parsers.*;
+import javax.xml.xpath.*;
+import org.w3c.dom.*;
+import org.xml.sax.*;
+
+/**
+ * This program evaluates XPath expressions.
+ * @version 1.02 2016-05-10
+ * @author Cay Horstmann
+ */
+public class XPathTester
+{
+   public static void main(String[] args)
+   {
+      EventQueue.invokeLater(() ->
+         {
+            JFrame frame = new XPathFrame();
+            frame.setTitle("XPathTest");
+            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+            frame.setVisible(true);
+         });
+   }
+}
+
+/**
+ * This frame shows an XML document, a panel to type an XPath expression, and a text field to
+ * display the result.
+ */
+class XPathFrame extends JFrame
+{
+   private DocumentBuilder builder;
+   private Document doc;
+   private XPath path;
+   private JTextField expression;
+   private JTextField result;
+   private JTextArea docText;
+   private JComboBox<String> typeCombo;
+
+   public XPathFrame()
+   {
+      JMenu fileMenu = new JMenu("File");
+      JMenuItem openItem = new JMenuItem("Open");
+      openItem.addActionListener(event -> openFile());
+      fileMenu.add(openItem);
+
+      JMenuItem exitItem = new JMenuItem("Exit");
+      exitItem.addActionListener(event -> System.exit(0));
+      fileMenu.add(exitItem);
+
+      JMenuBar menuBar = new JMenuBar();
+      menuBar.add(fileMenu);
+      setJMenuBar(menuBar);
+
+      ActionListener listener = event -> evaluate();
+      expression = new JTextField(20);
+      expression.addActionListener(listener);
+      JButton evaluateButton = new JButton("Evaluate");
+      evaluateButton.addActionListener(listener);
+
+      typeCombo = new JComboBox<String>(new String[] { 
+         "STRING", "NODE", "NODESET", "NUMBER", "BOOLEAN" });
+      typeCombo.setSelectedItem("STRING");
+
+      JPanel panel = new JPanel();
+      panel.add(expression);
+      panel.add(typeCombo);
+      panel.add(evaluateButton);
+      docText = new JTextArea(10, 40);
+      result = new JTextField();
+      result.setBorder(new TitledBorder("Result"));
+
+      add(panel, BorderLayout.NORTH);
+      add(new JScrollPane(docText), BorderLayout.CENTER);
+      add(result, BorderLayout.SOUTH);
+
+      try
+      {
+         DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+         builder = factory.newDocumentBuilder();
+      }
+      catch (ParserConfigurationException e)
+      {
+         JOptionPane.showMessageDialog(this, e);
+      }
+
+      XPathFactory xpfactory = XPathFactory.newInstance();
+      path = xpfactory.newXPath();
+      pack();
+   }
+
+   /**
+    * Open a file and load the document.
+    */
+   public void openFile()
+   {
+      JFileChooser chooser = new JFileChooser();
+      chooser.setCurrentDirectory(new File("xpath"));
+
+      chooser.setFileFilter(new javax.swing.filechooser.FileNameExtensionFilter("XML files", "xml"));
+      int r = chooser.showOpenDialog(this);
+      if (r != JFileChooser.APPROVE_OPTION) return;
+      File file = chooser.getSelectedFile();
+      try
+      {
+         docText.setText(new String(Files.readAllBytes(file.toPath())));
+         doc = builder.parse(file);
+      }
+      catch (IOException e)
+      {
+         JOptionPane.showMessageDialog(this, e);
+      }
+      catch (SAXException e)
+      {
+         JOptionPane.showMessageDialog(this, e);
+      }
+   }
+
+   public void evaluate()
+   {
+      try
+      {
+         String typeName = (String) typeCombo.getSelectedItem();
+         QName returnType = (QName) XPathConstants.class.getField(typeName).get(null);
+         Object evalResult = path.evaluate(expression.getText(), doc, returnType);
+         if (typeName.equals("NODESET"))
+         {
+            NodeList list = (NodeList) evalResult;
+            // Can't use String.join since NodeList isn't Iterable
+            StringJoiner joiner = new StringJoiner(",", "{", "}");
+            for (int i = 0; i < list.getLength(); i++)
+               joiner.add("" + list.item(i));
+            result.setText("" + joiner);
+         }
+         else result.setText("" + evalResult);
+      }
+      catch (XPathExpressionException e)
+      {
+         result.setText("" + e);
+      }
+      catch (Exception e) // reflection exception
+      {
+         e.printStackTrace();
+      }
+   }
+}