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Opis:
Sprawny crawler do przeszukiwania sieci. W zadanym url wyszukuje określone słowo i rekurencyjnie przechodzi przez podstrony. Napisany przez Schildta ('The art of java', polskie tłum. 'Java. Sztuka programowania'). Bardzo instruktywny, może stanowić dobry początek własnego szperacza.

Język: java


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.PLA IN));
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);
li mitCheckBox.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);
limi tCheckBox.setEnabled(true);
logTextField.setEnabled(true);
searchTextField.set Enabled(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);
matchesL abel2.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("<as+hrefs*=s*"?(.*?)["|>]",Pattern.CASE_INSENSITIVE);
Match er 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();
}
}
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Tagi do źródła:
java, crawler, przeszukiwanie sieci, robot sieciowy, java


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