转自 Crawling the Web with Java By James Holmes
无需任何扩展包，可直接运行。
import java.awt.*; import java.awt.event.*; import java.io.*; import java.net.*; import java.util.*; import java.util.regex.*; import javax.swing.*; import javax.swing.table.*; // 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(" "); } } 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; } } /* Loop through disallow list to see if crawling is allowed for the given URL. */ String file = urlToCheck.getFile(); for (int i = 0; i < disallowList.size(); i++) { String disallow = (String) disallowList.get(i); if (file.startsWith(disallow)) { return false; } } return true; } // Download page at given URL. private String downloadPage(URL pageUrl) { try { // Open connection to URL for reading. BufferedReader reader = new BufferedReader(new InputStreamReader( pageUrl.openStream())); // Read page into buffer. String line; StringBuffer pageBuffer = new StringBuffer(); while ((line = reader.readLine()) != null) { pageBuffer.append(line); } return pageBuffer.toString(); } catch (Exception e) { } return null; } // Remove leading "www" from a URL's host if present. private String removeWwwFromUrl(String url) { int index = url.indexOf("://www."); if (index != -1) { return url.substring(0, index + 3) + url.substring(index + 7); } return (url); } // Parse through page contents and retrieve links. private ArrayList retrieveLinks( URL pageUrl, String pageContents, HashSet crawledList, boolean limitHost) { // Compile link matching pattern. Pattern p = Pattern.compile("<a\s+href\s*=\s*"?(.*?)["|>]", Pattern.CASE_INSENSITIVE); Matcher m = p.matcher(pageContents); // Create list of link matches. ArrayList linkList = new ArrayList(); while (m.find()) { String link = m.group(1).trim(); // Skip empty links. if (link.length() < 1) { continue; } // Skip links that are just page anchors. if (link.charAt(0) == '#') { continue; } // Skip mailto links. if (link.indexOf("mailto:") != -1) { continue; } // Skip JavaScript links. if (link.toLowerCase().indexOf("javascript") != -1) { continue; } // Prefix absolute and relative URLs if necessary. if (link.indexOf("://") == -1) { // Handle absolute URLs. if (link.charAt(0) == '/') { link = "http://" + pageUrl.getHost() + link; // Handle relative URLs. } else { String file = pageUrl.getFile(); if (file.indexOf('/') == -1) { link = "http://" + pageUrl.getHost() + "/" + link; } else { String path = file.substring(0, file.lastIndexOf('/') + 1); link = "http://" + pageUrl.getHost() + path + link; } } } // Remove anchors from link. int index = link.indexOf('#'); if (index != -1) { link = link.substring(0, index); } // Remove leading "www" from URL's host if present. link = removeWwwFromUrl(link); // Verify link and skip if invalid. URL verifiedLink = verifyUrl(link); if (verifiedLink == null) { continue; } /* If specified, limit links to those having the same host as the start URL. */ if (limitHost && !pageUrl.getHost().toLowerCase().equals( verifiedLink.getHost().toLowerCase())) { continue; } // Skip link if it has already been crawled. if (crawledList.contains(link)) { continue; } // Add link to list. linkList.add(link); } return (linkList); } /* Determine whether or not search string is matched in the given page contents. */ private boolean searchStringMatches( String pageContents, String searchString, boolean caseSensitive) { String searchContents = pageContents; /* If case-sensitive search, lowercase page contents for comparison. */ if (!caseSensitive) { searchContents = pageContents.toLowerCase(); }// Split search string into individual terms. Pattern p = Pattern.compile("[\s]+"); String[] terms = p.split(searchString); // Check to see if each term matches. for (int i = 0; i < terms.length; i++) { if (caseSensitive) { if (searchContents.indexOf(terms[i]) == -1) { return false; } } else { if (searchContents.indexOf(terms[i].toLowerCase()) == -1) { return false; } } } return true; } // Perform the actual crawling, searching for the search string. public void crawl( String startUrl, int maxUrls, boolean limitHost, String searchString, boolean caseSensitive) { // Set up crawl lists. HashSet crawledList = new HashSet(); LinkedHashSet toCrawlList = new LinkedHashSet(); // Add start URL to the to crawl list. toCrawlList.add(startUrl); /* Perform actual crawling by looping through the To Crawl list. */ while (crawling && toCrawlList.size() > 0) { /* Check to see if the max URL count has been reached, if it was specified.*/ if (maxUrls != -1) { if (crawledList.size() == maxUrls) { break; } } // Get URL at bottom of the list. String url = (String) toCrawlList.iterator().next(); // Remove URL from the To Crawl list. toCrawlList.remove(url); // Convert string url to URL object. URL verifiedUrl = verifyUrl(url); // Skip URL if robots are not allowed to access it. if (!isRobotAllowed(verifiedUrl)) { continue; } // Update crawling stats. updateStats(url, crawledList.size(), toCrawlList.size(), maxUrls); // Add page to the crawled list. crawledList.add(url); // Download the page at the given URL. String pageContents = downloadPage(verifiedUrl); /* If the page was downloaded successfully, retrieve all its links and then see if it contains the search string. */ if (pageContents != null && pageContents.length() > 0) { // Retrieve list of valid links from page. ArrayList links = retrieveLinks(verifiedUrl, pageContents, crawledList, limitHost); // Add links to the To Crawl list. toCrawlList.addAll(links); /* Check if search string is present in page, and if so, record a match. */ if (searchStringMatches(pageContents, searchString, caseSensitive)) { addMatch(url); } } // Update crawling stats. updateStats(url, crawledList.size(), toCrawlList.size(), maxUrls); } } // Run the Search Crawler. public static void main(String[] args) { SearchCrawler crawler = new SearchCrawler(); crawler.show(); } }