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// The SearchCrawler class is shown here and is examined in detail in the
// following sections. Notice that it extends JFrame:
/*
* Chapter 6 - Crawling the Web with Java
* The Art of Java
* by Herbert Schildt and James Holmes
* McGraw-Hill/Osborne 2003
*
*/
import java.awt.BorderLayout;
import java.awt.Cursor;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedReader;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JSeparator;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;
// The Search Web Crawler
public class SearchCrawler extends JFrame {
// Max URLs drop-down values.
private static final String[] MAX_URLS = { "50", "100", "500", "1000" };
// Cache of robot disallow lists.
private HashMap disallowListCache = new HashMap();
// Search GUI controls.
private JTextField startTextField;
private JComboBox maxComboBox;
private JCheckBox limitCheckBox;
private JTextField logTextField;
private JTextField searchTextField;
private JCheckBox caseCheckBox;
private JButton searchButton;
// Search stats GUI controls.
private JLabel crawlingLabel2;
private JLabel crawledLabel2;
private JLabel toCrawlLabel2;
private JProgressBar progressBar;
private JLabel matchesLabel2;
// Table listing search matches.
private JTable table;
// Flag for whether or not crawling is underway.
private boolean crawling;
// Matches log file print writer.
private PrintWriter logFileWriter;
// Constructor for Search Web Crawler.
public SearchCrawler() {
// Set application title.
setTitle("Search Crawler");
// Set window size.
setSize(600, 600);
// Handle window closing events.
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
actionExit();
}
});
// Set up File menu.
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
fileMenu.setMnemonic(KeyEvent.VK_F);
JMenuItem fileExitMenuItem = new JMenuItem("Exit", KeyEvent.VK_X);
fileExitMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionExit();
}
});
fileMenu.add(fileExitMenuItem);
menuBar.add(fileMenu);
setJMenuBar(menuBar);
// Set up search panel.
JPanel searchPanel = new JPanel();
GridBagConstraints constraints;
GridBagLayout layout = new GridBagLayout();
searchPanel.setLayout(layout);
JLabel startLabel = new JLabel("Start URL:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(startLabel, constraints);
searchPanel.add(startLabel);
startTextField = new JTextField();
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(startTextField, constraints);
searchPanel.add(startTextField);
JLabel maxLabel = new JLabel("Max URLs to Crawl:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(maxLabel, constraints);
searchPanel.add(maxLabel);
maxComboBox = new JComboBox(MAX_URLS);
maxComboBox.setEditable(true);
constraints = new GridBagConstraints();
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(maxComboBox, constraints);
searchPanel.add(maxComboBox);
limitCheckBox = new JCheckBox("Limit crawling to Start URL site");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.WEST;
constraints.insets = new Insets(0, 10, 0, 0);
layout.setConstraints(limitCheckBox, constraints);
searchPanel.add(limitCheckBox);
JLabel blankLabel = new JLabel();
constraints = new GridBagConstraints();
constraints.gridwidth = GridBagConstraints.REMAINDER;
layout.setConstraints(blankLabel, constraints);
searchPanel.add(blankLabel);
JLabel logLabel = new JLabel("Matches Log File:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(logLabel, constraints);
searchPanel.add(logLabel);
String file = System.getProperty("user.dir")
+ System.getProperty("file.separator") + "crawler.log";
logTextField = new JTextField(file);
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(logTextField, constraints);
searchPanel.add(logTextField);
JLabel searchLabel = new JLabel("Search String:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(searchLabel, constraints);
searchPanel.add(searchLabel);
searchTextField = new JTextField();
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.insets = new Insets(5, 5, 0, 0);
constraints.gridwidth = 2;
constraints.weightx = 1.0d;
layout.setConstraints(searchTextField, constraints);
searchPanel.add(searchTextField);
caseCheckBox = new JCheckBox("Case Sensitive");
constraints = new GridBagConstraints();
constraints.insets = new Insets(5, 5, 0, 5);
constraints.gridwidth = GridBagConstraints.REMAINDER;
layout.setConstraints(caseCheckBox, constraints);
searchPanel.add(caseCheckBox);
searchButton = new JButton("Search");
searchButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionSearch();
}
});
constraints = new GridBagConstraints();
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 5, 5);
layout.setConstraints(searchButton, constraints);
searchPanel.add(searchButton);
JSeparator separator = new JSeparator();
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 5, 5);
layout.setConstraints(separator, constraints);
searchPanel.add(separator);
JLabel crawlingLabel1 = new JLabel("Crawling:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(crawlingLabel1, constraints);
searchPanel.add(crawlingLabel1);
crawlingLabel2 = new JLabel();
crawlingLabel2.setFont(crawlingLabel2.getFont().deriveFont(Font.PLAIN));
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(crawlingLabel2, constraints);
searchPanel.add(crawlingLabel2);
JLabel crawledLabel1 = new JLabel("Crawled URLs:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(crawledLabel1, constraints);
searchPanel.add(crawledLabel1);
crawledLabel2 = new JLabel();
crawledLabel2.setFont(crawledLabel2.getFont().deriveFont(Font.PLAIN));
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(crawledLabel2, constraints);
searchPanel.add(crawledLabel2);
JLabel toCrawlLabel1 = new JLabel("URLs to Crawl:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(toCrawlLabel1, constraints);
searchPanel.add(toCrawlLabel1);
toCrawlLabel2 = new JLabel();
toCrawlLabel2.setFont(toCrawlLabel2.getFont().deriveFont(Font.PLAIN));
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(toCrawlLabel2, constraints);
searchPanel.add(toCrawlLabel2);
JLabel progressLabel = new JLabel("Crawling Progress:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 0, 0);
layout.setConstraints(progressLabel, constraints);
searchPanel.add(progressLabel);
progressBar = new JProgressBar();
progressBar.setMinimum(0);
progressBar.setStringPainted(true);
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 0, 5);
layout.setConstraints(progressBar, constraints);
searchPanel.add(progressBar);
JLabel matchesLabel1 = new JLabel("Search Matches:");
constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.EAST;
constraints.insets = new Insets(5, 5, 10, 0);
layout.setConstraints(matchesLabel1, constraints);
searchPanel.add(matchesLabel1);
matchesLabel2 = new JLabel();
matchesLabel2.setFont(matchesLabel2.getFont().deriveFont(Font.PLAIN));
constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.gridwidth = GridBagConstraints.REMAINDER;
constraints.insets = new Insets(5, 5, 10, 5);
layout.setConstraints(matchesLabel2, constraints);
searchPanel.add(matchesLabel2);
// Set up matches table.
table = new JTable(new DefaultTableModel(new Object[][] {},
new String[] { "URL" }) {
public boolean isCellEditable(int row, int column) {
return false;
}
});
// Set up Matches panel.
JPanel matchesPanel = new JPanel();
matchesPanel.setBorder(BorderFactory.createTitledBorder("Matches"));
matchesPanel.setLayout(new BorderLayout());
matchesPanel.add(new JScrollPane(table), BorderLayout.CENTER);
// Add panels to display.
getContentPane().setLayout(new BorderLayout());
getContentPane().add(searchPanel, BorderLayout.NORTH);
getContentPane().add(matchesPanel, BorderLayout.CENTER);
}
// Exit this program.
private void actionExit() {
System.exit(0);
}
// Handle Search/Stop button being clicked.
private void actionSearch() {
// If stop button clicked, turn crawling flag off.
if (crawling) {
crawling = false;
return;
}
ArrayList errorList = new ArrayList();
// Validate that start URL has been entered.
String startUrl = startTextField.getText().trim();
if (startUrl.length() < 1) {
errorList.add("Missing Start URL.");
}
// Verify start URL.
else if (verifyUrl(startUrl) == null) {
errorList.add("Invalid Start URL.");
}
// Validate that Max URLs is either empty or is a number.
int maxUrls = 0;
String max = ((String) maxComboBox.getSelectedItem()).trim();
if (max.length() > 0) {
try {
maxUrls = Integer.parseInt(max);
} catch (NumberFormatException e) {
}
if (maxUrls < 1) {
errorList.add("Invalid Max URLs value.");
}
}
// Validate that matches log file has been entered.
String logFile = logTextField.getText().trim();
if (logFile.length() < 1) {
errorList.add("Missing Matches Log File.");
}
// Validate that search string has been entered.
String searchString = searchTextField.getText().trim();
if (searchString.length() < 1) {
errorList.add("Missing Search String.");
}
// Show errors, if any, and return.
if (errorList.size() > 0) {
StringBuffer message = new StringBuffer();
// Concatenate errors into single message.
for (int i = 0; i < errorList.size(); i++) {
message.append(errorList.get(i));
if (i + 1 < errorList.size()) {
message.append("\n");
}
}
showError(message.toString());
return;
}
// Remove "www" from start URL if present.
startUrl = removeWwwFromUrl(startUrl);
// Start the Search Crawler.
search(logFile, startUrl, maxUrls, searchString);
}
private void search(final String logFile, final String startUrl,
final int maxUrls, final String searchString) {
// Start the search in a new thread.
Thread thread = new Thread(new Runnable() {
public void run() {
// Show hour glass cursor while crawling is under way.
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
// Disable search controls.
startTextField.setEnabled(false);
maxComboBox.setEnabled(false);
limitCheckBox.setEnabled(false);
logTextField.setEnabled(false);
searchTextField.setEnabled(false);
caseCheckBox.setEnabled(false);
// Switch Search button to "Stop."
searchButton.setText("Stop");
// Reset stats.
table.setModel(new DefaultTableModel(new Object[][] {},
new String[] { "URL" }) {
public boolean isCellEditable(int row, int column) {
return false;
}
});
updateStats(startUrl, 0, 0, maxUrls);
// Open matches log file.
try {
logFileWriter = new PrintWriter(new FileWriter(logFile));
} catch (Exception e) {
showError("Unable to open matches log file.");
return;
}
// Turn crawling flag on.
crawling = true;
// Perform the actual crawling.
crawl(startUrl, maxUrls, limitCheckBox.isSelected(),
searchString, caseCheckBox.isSelected());
// Turn crawling flag off.
crawling = false;
// Close matches log file.
try {
logFileWriter.close();
} catch (Exception e) {
showError("Unable to close matches log file.");
}
// Mark search as done.
crawlingLabel2.setText("Done");
// Enable search controls.
startTextField.setEnabled(true);
maxComboBox.setEnabled(true);
limitCheckBox.setEnabled(true);
logTextField.setEnabled(true);
searchTextField.setEnabled(true);
caseCheckBox.setEnabled(true);
// Switch search button back to "Search."
searchButton.setText("Search");
// Return to default cursor.
setCursor(Cursor.getDefaultCursor());
// Show message if search string not found.
if (table.getRowCount() == 0) {
JOptionPane
.showMessageDialog(
SearchCrawler.this,
"Your Search String was not found. Please try another.",
"Search String Not Found",
JOptionPane.WARNING_MESSAGE);
}
}
});
thread.start();
}
// Show dialog box with error message.
private void showError(String message) {
JOptionPane.showMessageDialog(this, message, "Error",
JOptionPane.ERROR_MESSAGE);
}
// Update crawling stats.
private void updateStats(String crawling, int crawled, int toCrawl,
int maxUrls) {
crawlingLabel2.setText(crawling);
crawledLabel2.setText("" + crawled);
toCrawlLabel2.setText("" + toCrawl);
// Update progress bar.
if (maxUrls == -1) {
progressBar.setMaximum(crawled + toCrawl);
} else {
progressBar.setMaximum(maxUrls);
}
progressBar.setValue(crawled);
matchesLabel2.setText("" + table.getRowCount());
}
// Add match to matches table and log file.
private void addMatch(String url) {
// Add URL to matches table.
DefaultTableModel model = (DefaultTableModel) table.getModel();
model.addRow(new Object[] { url });
// Add URL to matches log file.
try {
logFileWriter.println(url);
} catch (Exception e) {
showError("Unable to log match.");
}
}
// Verify URL format.
private URL verifyUrl(String url) {
// Only allow HTTP URLs.
if (!url.toLowerCase().startsWith("http://"))
return null;
// Verify format of URL.
URL verifiedUrl = null;
try {
verifiedUrl = new URL(url);
} catch (Exception e) {
return null;
}
return verifiedUrl;
}
// Check if robot is allowed to access the given URL.
private boolean isRobotAllowed(URL urlToCheck) {
String host = urlToCheck.getHost().toLowerCase();
// Retrieve host's disallow list from cache.
ArrayList disallowList = (ArrayList) disallowListCache.get(host);
// If list is not in the cache, download and cache it.
if (disallowList == null) {
disallowList = new ArrayList();
try {
URL robotsFileUrl = new URL("http://" + host + "/robots.txt");
// Open connection to robot file URL for reading.
BufferedReader reader = new BufferedReader(
new InputStreamReader(robotsFileUrl.openStream()));
// Read robot file, creating list of disallowed paths.
String line;
while ((line = reader.readLine()) != null) {
if (line.indexOf("Disallow:") == 0) {
String disallowPath = line.substring("Disallow:"
.length());
// Check disallow path for comments and remove if
// present.
int commentIndex = disallowPath.indexOf("#");
if (commentIndex != -1) {
disallowPath = disallowPath.substring(0,
commentIndex);
}
// Remove leading or trailing spaces from disallow path.
disallowPath = disallowPath.trim();
// Add disallow path to list.
disallowList.add(disallowPath);
}
}
// Add new disallow list to cache.
disallowListCache.put(host, disallowList);
} catch (Exception e) {
/*
* Assume robot is allowed since an exception is thrown if the
* robot file doesn't exist.
*/
return true;
}
}
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