Programming a Spider in Java 源码帖
Listing 1: Finding the bad links (CheckLinks.java)
import java.awt.*;
import javax.swing.*;
import java.net.*;
import java.io.*;
/**
* This example uses a Java spider to scan a Web site
* and check for broken links. Written by Jeff Heaton.
* Jeff Heaton is the author of "Programming Spiders,
* Bots, and Aggregators" by Sybex. Jeff can be contacted
* through his Web site at http://www.jeffheaton.com.
*
* @author Jeff Heaton(http://www.jeffheaton.com)
* @version 1.0
*/
public class CheckLinks extends javax.swing.JFrame implements Runnable,ISpiderReportable {
/**
* The constructor. Perform setup here.
*/
public CheckLinks() {
//{{INIT_CONTROLS
setTitle("Find Broken Links");
getContentPane().setLayout(null);
setSize(405,288);
setVisible(false);
label1.setText("Enter a URL:");
getContentPane().add(label1);
label1.setBounds(12,12,84,12);
begin.setText("Begin");
begin.setActionCommand("Begin");
getContentPane().add(begin);
begin.setBounds(12,36,84,24);
getContentPane().add(url);
url.setBounds(108,36,288,24);
errorScroll.setAutoscrolls(true);
errorScroll.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
errorScroll.setVerticalScrollBarPolicy(javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
errorScroll.setOpaque(true);
getContentPane().add(errorScroll);
errorScroll.setBounds(12,120,384,156);
errors.setEditable(false);
errorScroll.getViewport().add(errors);
errors.setBounds(0,0,366,138);
current.setText("Currently Processing: ");
getContentPane().add(current);
current.setBounds(12,72,384,12);
goodLinksLabel.setText("Good Links: 0");
getContentPane().add(goodLinksLabel);
goodLinksLabel.setBounds(12,96,192,12);
badLinksLabel.setText("Bad Links: 0");
getContentPane().add(badLinksLabel);
badLinksLabel.setBounds(216,96,96,12);
//}}
//{{INIT_MENUS
//}}
//{{REGISTER_LISTENERS
SymAction lSymAction = new SymAction();
begin.addActionListener(lSymAction);
//}}
}
/**
* Main method for the application
*
* @param args Not used
*/
static public void main(String args[]){
(new CheckLinks()).setVisible(true);
}
/**
* Add notifications.
*/
public void addNotify(){
// Record the size of the window prior to calling parent's
// addNotify.
Dimension size = getSize();
super.addNotify();
if ( frameSizeAdjusted )
return;
frameSizeAdjusted = true;
// Adjust size of frame according to the insets and menu bar
Insets insets = getInsets();
javax.swing.JMenuBar menuBar = getRootPane().getJMenuBar();
int menuBarHeight = 0;
if ( menuBar != null )
menuBarHeight = menuBar.getPreferredSize().height;
setSize(insets.left + insets.right + size.width, insets.top + insets.bottom + size.height + menuBarHeight);
}
// Used by addNotify
boolean frameSizeAdjusted = false;
//{{DECLARE_CONTROLS
javax.swing.JLabel label1 = new javax.swing.JLabel();
/**
* The begin or cancel button
*/
javax.swing.JButton begin = new javax.swing.JButton();
/**
* The URL being processed
*/
javax.swing.JTextField url = new javax.swing.JTextField();
/**
* Scroll the errors.
*/
javax.swing.JScrollPane errorScroll = new javax.swing.JScrollPane();
/**
* A place to store the errors created
*/
javax.swing.JTextArea errors = new javax.swing.JTextArea();
javax.swing.JLabel current = new javax.swing.JLabel();
javax.swing.JLabel goodLinksLabel = new javax.swing.JLabel();
javax.swing.JLabel badLinksLabel = new javax.swing.JLabel();
//}}
//{{DECLARE_MENUS
//}}
/**
* The background spider thread
*/
protected Thread backgroundThread;
/**
* The spider object being used
*/
protected Spider spider;
/**
* The URL that the spider began with
*/
protected URL base;
/**
* How many bad links have been found
*/
protected int badLinksCount = 0;
/**
* How many good links have been found
*/
protected int goodLinksCount = 0;
/**
* Internal class used to dispatch events
*
* @author Jeff Heaton
* @version 1.0
*/
class SymAction implements java.awt.event.ActionListener {
public void actionPerformed(java.awt.event.ActionEvent event){
Object object = event.getSource();
if ( object == begin )
begin_actionPerformed(event);
}
}
/**
* Called when the begin or cancel buttons are clicked
*
* @param event The event associated with the button.
*/
void begin_actionPerformed(java.awt.event.ActionEvent event){
if ( backgroundThread==null ) {
begin.setLabel("Cancel");
backgroundThread = new Thread(this);
backgroundThread.start();
goodLinksCount=0;
badLinksCount=0;
} else {
spider.cancel();
}
}
/**
* Perform the background thread operation. This method
* actually starts the background thread.
*/
public void run(){
try {
errors.setText("");
spider = new Spider(this);
spider.clear();
base = new URL(url.getText());
spider.addURL(base);
spider.begin();
Runnable doLater = new Runnable(){
public void run(){
begin.setText("Begin");
}
};
SwingUtilities.invokeLater(doLater);
backgroundThread=null;
} catch ( MalformedURLException e ) {
UpdateErrors err = new UpdateErrors();
err.msg = "Bad address.";
SwingUtilities.invokeLater(err);
}
}
/**
* Called by the spider when a URL is found. It is here
* that links are validated.
*
* @param base The page that the link was found on.
* @param url The actual link address.
*/
public boolean spiderFoundURL(URL base,URL url){
UpdateCurrentStats cs = new UpdateCurrentStats();
cs.msg = url.toString();
SwingUtilities.invokeLater(cs);
if ( !checkLink(url) ) {
UpdateErrors err = new UpdateErrors();
err.msg = url+"(on page " + base + ")
";
SwingUtilities.invokeLater(err);
badLinksCount++;
return false;
}
goodLinksCount++;
if ( !url.getHost().equalsIgnoreCase(base.getHost()) )
return false;
else
return true;
}
/**
* Called when a URL error is found
*
* @param url The URL that resulted in an error.
*/
public void spiderURLError(URL url){
}
/**
* Called internally to check whether a link is good
*
* @param url The link that is being checked.
* @return True if the link was good, false otherwise.
*/
protected boolean checkLink(URL url){
try {
URLConnection connection = url.openConnection();
connection.connect();
return true;
} catch ( IOException e ) {
return false;
}
}
/**
* Called when the spider finds an e-mail address
*
* @param email The email address the spider found.
*/
public void spiderFoundEMail(String email){
}
/**
* Internal class used to update the error information
* in a Thread-Safe way
*
* @author Jeff Heaton
* @version 1.0
*/
class UpdateErrors implements Runnable {
public String msg;
public void run(){
errors.append(msg);
}
}
/**
* Used to update the current status information
* in a "Thread-Safe" way
*
* @author Jeff Heaton
* @version 1.0
*/
class UpdateCurrentStats implements Runnable {
public String msg;
public void run(){
current.setText("Currently Processing: " + msg );
goodLinksLabel.setText("Good Links: " + goodLinksCount);
badLinksLabel.setText("Bad Links: " + badLinksCount);
}
}
}
Listing 2: Reporting spider events(ISpiderReportable.java)
import java.net.*;
interface ISpiderReportable {
public boolean spiderFoundURL(URL base,URL url);
public void spiderURLError(URL url);
public void spiderFoundEMail(String email);
}
Listing 3: A reusable spider (Spider.java)
import java.util.*;
import java.net.*;
import java.io.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
/**
* That class implements a reusable spider
*
* @author Jeff Heaton(http://www.jeffheaton.com)
* @version 1.0
*/
public class Spider {
/**
* A collection of URLs that resulted in an error
*/
protected Collection workloadError = new ArrayList(3);
/**
* A collection of URLs that are waiting to be processed
*/
protected Collection workloadWaiting = new ArrayList(3);
/**
* A collection of URLs that were processed
*/
protected Collection workloadProcessed = new ArrayList(3);
/**
* The class that the spider should report its URLs to
*/
protected ISpiderReportable report;
/**
* A flag that indicates whether this process
* should be canceled
*/
protected boolean cancel = false;
/**
* The constructor
*
* @param report A class that implements the ISpiderReportable
* interface, that will receive information that the
* spider finds.
*/
public Spider(ISpiderReportable report){
this.report = report;
}
/**
* Get the URLs that resulted in an error.
*
* @return A collection of URL's.
*/
public Collection getWorkloadError(){
return workloadError;
}
/**
* Get the URLs that were waiting to be processed.
* You should add one URL to this collection to
* begin the spider.
*
* @return A collection of URLs.
*/
public Collection getWorkloadWaiting(){
return workloadWaiting;
}
/**
* Get the URLs that were processed by this spider.
*
* @return A collection of URLs.
*/
public Collection getWorkloadProcessed(){
return workloadProcessed;
}
/**
* Clear all of the workloads.
*/
public void clear(){
getWorkloadError().clear();
getWorkloadWaiting().clear();
getWorkloadProcessed().clear();
}
/**
* Set a flag that will cause the begin
* method to return before it is done.
*/
public void cancel(){
cancel = true;
}
/**
* Add a URL for processing.
*
* @param url
*/
public void addURL(URL url){
if ( getWorkloadWaiting().contains(url) )
return;
if ( getWorkloadError().contains(url) )
return;
if ( getWorkloadProcessed().contains(url) )
return;
log("Adding to workload: " + url );
getWorkloadWaiting().add(url);
}
/**
* Called internally to process a URL
*
* @param url The URL to be processed.
*/
public void processURL(URL url){
try {
log("Processing: " + url );
// get the URL's contents
URLConnection connection = url.openConnection();
if ( (connection.getContentType()!=null) && !connection.getContentType().toLowerCase().startsWith("text/") ) {
getWorkloadWaiting().remove(url);
getWorkloadProcessed().add(url);
log("Not processing because content type is: " + connection.getContentType() );
return;
}
// read the URL
InputStream is = connection.getInputStream();
Reader r = new InputStreamReader(is);
// parse the URL
HTMLEditorKit.Parser parse = new HTMLParse().getParser();
parse.parse(r,new Parser(url),true);
} catch ( IOException e ) {
getWorkloadWaiting().remove(url);
getWorkloadError().add(url);
log("Error: " + url );
report.spiderURLError(url);
return;
}
// mark URL as complete
getWorkloadWaiting().remove(url);
getWorkloadProcessed().add(url);
log("Complete: " + url );
}
/**
* Called to start the spider
*/
public void begin(){
cancel = false;
while ( !getWorkloadWaiting().isEmpty() && !cancel ) {
Object list[] = getWorkloadWaiting().toArray();
for ( int i=0;(i<list.length)&&!cancel;i++ )
processURL((URL)list[i]);
}
}
/**
* A HTML parser callback used by this class to detect links
*
* @author Jeff Heaton
* @version 1.0
*/
protected class Parser
extends HTMLEditorKit.ParserCallback {
protected URL base;
public Parser(URL base){
this.base = base;
}
public void handleSimpleTag(HTML.Tag t, MutableAttributeSet a,int pos){
String href = (String)a.getAttribute(HTML.Attribute.HREF);
if( (href==null) && (t==HTML.Tag.FRAME) )
href = (String)a.getAttribute(HTML.Attribute.SRC);
if ( href==null )
return;
int i = href.indexOf('#');
if ( i!=-1 )
href = href.substring(0,i);
if ( href.toLowerCase().startsWith("mailt") ) {
report.spiderFoundEMail(href);
return;
}
handleLink(base,href);
}
public void handleStartTag(HTML.Tag t, MutableAttributeSet a,int pos){
handleSimpleTag(t,a,pos); // handle the same way
}
protected void handleLink(URL base,String str){
try {
URL url = new URL(base,str);
if ( report.spiderFoundURL(base,url) )
addURL(url);
} catch ( MalformedURLException e ) {
log("Found malformed URL: " + str );
}
}
}
/**
* Called internally to log information
* This basic method just writes the log
* out to the stdout.
*
* @param entry The information to be written to the log.
*/
public void log(String entry){
System.out.println( (new Date()) + ":" + entry );
}
}
Listing 4: Parsing HTML (HTMLParse.java)
import javax.swing.text.html.*;
public class HTMLParse extends HTMLEditorKit {
public HTMLEditorKit.Parser getParser(){
return super.getParser();
}
}