Java網(wǎng)絡(luò)爬蟲怎么實(shí)現(xiàn)？

網(wǎng)絡(luò)爬蟲是一個(gè)自動提取網(wǎng)頁的程序，它為搜索引擎從萬維網(wǎng)上下載網(wǎng)頁，是搜索引擎的重要組成。\x0d\x0a傳統(tǒng)爬蟲從一個(gè)或若干初始網(wǎng)頁的URL開始，獲得初始網(wǎng)頁上的URL，在抓取網(wǎng)頁的過程中，不斷從當(dāng)前頁面上抽取新的URL放入隊(duì)列，直到滿足系統(tǒng)的一定停止條件。對于垂直搜索來說，聚焦爬蟲，即有針對性地爬取特定主題網(wǎng)頁的爬蟲，更為適合。\x0d\x0a\x0d\x0a以下是一個(gè)使用java實(shí)現(xiàn)的簡單爬蟲核心代碼：\x0d\x0apublic void crawl() throws Throwable { \x0d\x0a while (continueCrawling()) { \x0d\x0a CrawlerUrl url = getNextUrl(); //獲取待爬取隊(duì)列中的下一個(gè)URL \x0d\x0a if (url != null) { \x0d\x0a printCrawlInfo(); \x0d\x0a String content = getContent(url); //獲取URL的文本信息 \x0d\x0a \x0d\x0a //聚焦爬蟲只爬取與主題內(nèi)容相關(guān)的網(wǎng)頁，這里采用正則匹配簡單處理 \x0d\x0a if (isContentRelevant(content, this.regexpSearchPattern)) { \x0d\x0a saveContent(url, content); //保存網(wǎng)頁至本地 \x0d\x0a \x0d\x0a //獲取網(wǎng)頁內(nèi)容中的鏈接，并放入待爬取隊(duì)列中 \x0d\x0a Collection urlStrings = extractUrls(content, url); \x0d\x0a addUrlsToUrlQueue(url, urlStrings); \x0d\x0a } else { \x0d\x0a System.out.println(url + " is not relevant ignoring ..."); \x0d\x0a } \x0d\x0a \x0d\x0a //延時(shí)防止被對方屏蔽 \x0d\x0a Thread.sleep(this.delayBetweenUrls); \x0d\x0a } \x0d\x0a } \x0d\x0a closeOutputStream(); \x0d\x0a}\x0d\x0aprivate CrawlerUrl getNextUrl() throws Throwable { \x0d\x0a CrawlerUrl nextUrl = null; \x0d\x0a while ((nextUrl == null) (!urlQueue.isEmpty())) { \x0d\x0a CrawlerUrl crawlerUrl = this.urlQueue.remove(); \x0d\x0a //doWeHavePermissionToVisit：是否有權(quán)限訪問該URL，友好的爬蟲會根據(jù)網(wǎng)站提供的"Robot.txt"中配置的規(guī)則進(jìn)行爬取 \x0d\x0a //isUrlAlreadyVisited：URL是否訪問過，大型的搜索引擎往往采用BloomFilter進(jìn)行排重，這里簡單使用HashMap \x0d\x0a //isDepthAcceptable：是否達(dá)到指定的深度上限。爬蟲一般采取廣度優(yōu)先的方式。一些網(wǎng)站會構(gòu)建爬蟲陷阱（自動生成一些無效鏈接使爬蟲陷入死循環(huán)），采用深度限制加以避免 \x0d\x0a if (doWeHavePermissionToVisit(crawlerUrl) \x0d\x0a (!isUrlAlreadyVisited(crawlerUrl)) \x0d\x0a isDepthAcceptable(crawlerUrl)) { \x0d\x0a nextUrl = crawlerUrl; \x0d\x0a // System.out.println("Next url to be visited is " + nextUrl); \x0d\x0a } \x0d\x0a } \x0d\x0a return nextUrl; \x0d\x0a}\x0d\x0aprivate String getContent(CrawlerUrl url) throws Throwable { \x0d\x0a //HttpClient4.1的調(diào)用與之前的方式不同 \x0d\x0a HttpClient client = new DefaultHttpClient(); \x0d\x0a HttpGet httpGet = new HttpGet(url.getUrlString()); \x0d\x0a StringBuffer strBuf = new StringBuffer(); \x0d\x0a HttpResponse response = client.execute(httpGet); \x0d\x0a if (HttpStatus.SC_OK == response.getStatusLine().getStatusCode()) { \x0d\x0a HttpEntity entity = response.getEntity(); \x0d\x0a if (entity != null) { \x0d\x0a BufferedReader reader = new BufferedReader( \x0d\x0a new InputStreamReader(entity.getContent(), "UTF-8")); \x0d\x0a String line = null; \x0d\x0a if (entity.getContentLength() 0) { \x0d\x0a strBuf = new StringBuffer((int) entity.getContentLength()); \x0d\x0a while ((line = reader.readLine()) != null) { \x0d\x0a strBuf.append(line); \x0d\x0a } \x0d\x0a } \x0d\x0a } \x0d\x0a if (entity != null) { \x0d\x0a nsumeContent(); \x0d\x0a } \x0d\x0a } \x0d\x0a //將url標(biāo)記為已訪問 \x0d\x0a markUrlAsVisited(url); \x0d\x0a return strBuf.toString(); \x0d\x0a}\x0d\x0apublic static boolean isContentRelevant(String content, \x0d\x0aPattern regexpPattern) { \x0d\x0a boolean retValue = false; \x0d\x0a if (content != null) { \x0d\x0a //是否符合正則表達(dá)式的條件 \x0d\x0a Matcher m = regexpPattern.matcher(content.toLowerCase()); \x0d\x0a retValue = m.find(); \x0d\x0a } \x0d\x0a return retValue; \x0d\x0a}\x0d\x0apublic List extractUrls(String text, CrawlerUrl crawlerUrl) { \x0d\x0a Map urlMap = new HashMap(); \x0d\x0a extractHttpUrls(urlMap, text); \x0d\x0a extractRelativeUrls(urlMap, text, crawlerUrl); \x0d\x0a return new ArrayList(urlMap.keySet()); \x0d\x0a} \x0d\x0aprivate void extractHttpUrls(Map urlMap, String text) { \x0d\x0a Matcher m = (text); \x0d\x0a while (m.find()) { \x0d\x0a String url = m.group(); \x0d\x0a String[] terms = url.split("a href=\""); \x0d\x0a for (String term : terms) { \x0d\x0a // System.out.println("Term = " + term); \x0d\x0a if (term.startsWith("http")) { \x0d\x0a int index = term.indexOf("\""); \x0d\x0a if (index 0) { \x0d\x0a term = term.substring(0, index); \x0d\x0a } \x0d\x0a urlMap.put(term, term); \x0d\x0a System.out.println("Hyperlink: " + term); \x0d\x0a } \x0d\x0a } \x0d\x0a } \x0d\x0a} \x0d\x0aprivate void extractRelativeUrls(Map urlMap, String text, \x0d\x0a CrawlerUrl crawlerUrl) { \x0d\x0a Matcher m = relativeRegexp.matcher(text); \x0d\x0a URL textURL = crawlerUrl.getURL(); \x0d\x0a String host = textURL.getHost(); \x0d\x0a while (m.find()) { \x0d\x0a String url = m.group(); \x0d\x0a String[] terms = url.split("a href=\""); \x0d\x0a for (String term : terms) { \x0d\x0a if (term.startsWith("/")) { \x0d\x0a int index = term.indexOf("\""); \x0d\x0a if (index 0) { \x0d\x0a term = term.substring(0, index); \x0d\x0a } \x0d\x0a String s = //" + host + term; \x0d\x0a urlMap.put(s, s); \x0d\x0a System.out.println("Relative url: " + s); \x0d\x0a } \x0d\x0a } \x0d\x0a } \x0d\x0a \x0d\x0a}\x0d\x0apublic static void main(String[] args) { \x0d\x0a try { \x0d\x0a String url = ""; \x0d\x0a Queue urlQueue = new LinkedList(); \x0d\x0a String regexp = "java"; \x0d\x0a urlQueue.add(new CrawlerUrl(url, 0)); \x0d\x0a NaiveCrawler crawler = new NaiveCrawler(urlQueue, 100, 5, 1000L, \x0d\x0a regexp); \x0d\x0a // boolean allowCrawl = crawler.areWeAllowedToVisit(url); \x0d\x0a // System.out.println("Allowed to crawl: " + url + " " + \x0d\x0a // allowCrawl); \x0d\x0a crawler.crawl(); \x0d\x0a } catch (Throwable t) { \x0d\x0a System.out.println(t.toString()); \x0d\x0a t.printStackTrace(); \x0d\x0a } \x0d\x0a}

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用java編寫 網(wǎng)絡(luò)爬蟲求代碼和流程 急

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.*;//一個(gè)Web的爬行者(注：爬行在這里的意思與抓取，捕獲相同)

public class SearchCrawler extends JFrame{

//最大URL保存值

private static final String[] MAX_URLS={"50","100","500","1000"};

//緩存robot禁止爬行列表

private HashMap disallowListCache=new HashMap();

//搜索GUI控件

private JTextField startTextField;

private JComboBox maxComboBox;

private JCheckBox limitCheckBox;

private JTextField logTextField;

private JTextField searchTextField;

private JCheckBox caseCheckBox;

private JButton searchButton;

//搜索狀態(tài)GUI控件

private JLabel crawlingLabel2;

private JLabel crawledLabel2;

private JLabel toCrawlLabel2;

private JProgressBar progressBar;

private JLabel matchesLabel2;

//搜索匹配項(xiàng)表格列表

private JTable table;

//標(biāo)記爬行機(jī)器是否正在爬行

private boolean crawling;

//寫日志匹配文件的引用

private PrintWriter logFileWriter;

//網(wǎng)絡(luò)爬行者的構(gòu)造函數(shù)

public SearchCrawler(){

//設(shè)置應(yīng)用程序標(biāo)題欄

setTitle("搜索爬行者");

//設(shè)置窗體大小

setSize(600,600);

//處理窗體關(guān)閉事件

addWindowListener(new WindowAdapter(){

public void windowClosing(WindowEvent e){

actionExit();

}

});

//設(shè)置文件菜單

JMenuBar menuBar=new JMenuBar();

JMenu fileMenu=new JMenu("文件");

fileMenu.setMnemonic(KeyEvent.VK_F);

JMenuItem fileExitMenuItem=new JMenuItem("退出",KeyEvent.VK_X);

fileExitMenuItem.addActionListener(new ActionListener(){

public void actionPerformed(ActionEvent e){

actionExit();

}

});

fileMenu.add(fileExitMenuItem);

menuBar.add(fileMenu);

setJMenuBar(menuBar);

如何用Java寫一個(gè)爬蟲

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import java.io.File;

import java.net.URL;

import java.net.URLConnection;

import java.nio.file.Files;

import java.nio.file.Paths;

import java.util.Scanner;

import java.util.UUID;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class DownMM {

public static void main(String[] args) throws Exception {

//out為輸出的路徑,注意要以\\結(jié)尾

String out = "D:\\JSP\\pic\\java\\";

try{

File f = new File(out);

if(! f.exists()) {

f.mkdirs();

}

}catch(Exception e){

System.out.println("no");

}

String url = "-";

Pattern reg = Pattern.compile("img src=\"(.*?)\"");

for(int j=0, i=1; i=10; i++){

URL uu = new URL(url+i);

URLConnection conn = uu.openConnection();

conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko");

Scanner sc = new Scanner(conn.getInputStream());

Matcher m = reg.matcher(sc.useDelimiter("\\A").next());

while(m.find()){

Files.copy(new URL(m.group(1)).openStream(), Paths.get(out + UUID.randomUUID() + ".jpg"));

System.out.println("已下載:"+j++);

}

}

}

當(dāng)前文章：java爬蟲代碼教程 Java爬蟲代碼
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