Java爬虫实践--爬取CSDN网站图片为例

实现的效果，自动在工程下创建Pictures文件夹，根据网站URL爬取图片，层层获取。在Pictures下以网站的层级URL命名文件夹，用来装该层URL下的图片。同时将文件名，路径，URL插入数据库，便于索引。

第一步，创建持久层类，用来存储文件名，路径以及URL。

package org.amuxia.demo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class JDBCHelper {
private static final String driver = "com.mysql.jdbc.Driver";
private static final String DBurl = "jdbc:mysql://127.0.0.1:3306/edupic";
private static final String user = "root";
private static final String password = "root";
private PreparedStatement pstmt = null;
private Connection spiderconn = null;

public void insertFilePath(String fileName, String filepath, String url) {
try {
Class.forName(driver);
spiderconn = DriverManager.getConnection(DBurl, user, password);
String sql = "insert into FilePath (filename,filepath,url) values (?,?,?)";
pstmt = spiderconn.prepareStatement(sql);
pstmt.setString(1, fileName);
pstmt.setString(2, filepath);
pstmt.setString(3, url);
pstmt.executeUpdate();

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
pstmt.close();
spiderconn.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}

第二步，创建解析URL的类，进行爬取

package org.amuxia.demo;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GetWeb {
private int webDepth = 5; // 爬虫深度
private int intThreadNum = 1; // 线程数
private String strHomePage = ""; // 主页地址
private String myDomain; // 域名
private String fPath = "CSDN"; // 储存网页文件的目录名
private ArrayList<String> arrUrls = new ArrayList<String>(); // 存储未处理URL
private ArrayList<String> arrUrl = new ArrayList<String>(); // 存储所有URL供建立索引
private Hashtable<String, Integer> allUrls = new Hashtable<String, Integer>(); // 存储所有URL的网页号
private Hashtable<String, Integer> deepUrls = new Hashtable<String, Integer>(); // 存储所有URL深度
private int intWebIndex = 0; // 网页对应文件下标，从0开始
private long startTime;
private int webSuccessed = 0;
private int webFailed = 0;

public static void main(String[] args) {
GetWeb gw = new GetWeb("http://www.csdn.net/");
gw.getWebByHomePage();
}

public GetWeb(String s) {
this.strHomePage = s;
}

public GetWeb(String s, int i) {
this.strHomePage = s;
this.webDepth = i;
}

public synchronized void addWebSuccessed() {
webSuccessed++;
}

public synchronized void addWebFailed() {
webFailed++;
}

public synchronized String getAUrl() {
String tmpAUrl = arrUrls.get(0);
arrUrls.remove(0);
return tmpAUrl;
}

public synchronized String getUrl() {
String tmpUrl = arrUrl.get(0);
arrUrl.remove(0);
return tmpUrl;
}

public synchronized Integer getIntWebIndex() {
intWebIndex++;
return intWebIndex;
}

/**
* 由用户提供的域名站点开始，对所有链接页面进行抓取
*/
public void getWebByHomePage() {
startTime = System.currentTimeMillis();
this.myDomain = getDomain();
if (myDomain == null) {
System.out.println("Wrong input!");
return;
}

System.out.println("Homepage = " + strHomePage);
System.out.println("Domain = " + myDomain);
arrUrls.add(strHomePage);
arrUrl.add(strHomePage);
allUrls.put(strHomePage, 0);
deepUrls.put(strHomePage, 1);

File fDir = new File(fPath);
if (!fDir.exists()) {
fDir.mkdir();
}

System.out.println("开始工作");
String tmp = getAUrl(); // 取出新的URL
this.getWebByUrl(tmp, allUrls.get(tmp) + ""); // 对新URL所对应的网页进行抓取
int i = 0;
for (i = 0; i < intThreadNum; i++) {
new Thread(new Processer(this)).start();
}
while (true) {
if (arrUrls.isEmpty() && Thread.activeCount() == 1) {
long finishTime = System.currentTimeMillis();
long costTime = finishTime - startTime;
System.out.println("\n\n\n\n\n完成");
System.out.println(
"开始时间 = " + startTime + "   " + "结束时间 = " + finishTime + "   " + "爬取总时间= " + costTime + "ms");
System.out.println("爬取的URL总数 = " + (webSuccessed + webFailed) + "   成功的URL总数: " + webSuccessed
+ "   失败的URL总数: " + webFailed);
String strIndex = "";
String tmpUrl = "";
while (!arrUrl.isEmpty()) {
tmpUrl = getUrl();
strIndex += "Web depth:" + deepUrls.get(tmpUrl) + "   Filepath: " + fPath + "/web"
+ allUrls.get(tmpUrl) + ".htm" + "url:" + tmpUrl + "\n\n";
}
System.out.println(strIndex);
try {
PrintWriter pwIndex = new PrintWriter(new FileOutputStream("fileindex.txt"));
pwIndex.println(strIndex);
pwIndex.close();
} catch (Exception e) {
System.out.println("生成索引文件失败!");
}
break;
}
}
}

/**
* 对后续解析的网站进行爬取
*
* @param strUrl
* @param fileIndex
*/
public void getWebByUrl(String strUrl, String fileIndex) {
try {
System.out.println("通过URL得到网站: " + strUrl);

URL url = new URL(strUrl);
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
InputStream is = null;
is = url.openStream();
String filename = strUrl.replaceAll("/", "_");
filename = filename.replace(":", ".");
if (filename.indexOf("*") > 0) {
filename = filename.replaceAll("*", ".");
}
if (filename.indexOf("?") > 0) {
filename = filename.replaceAll("?", ".");
}
if (filename.indexOf("\"") > 0) {
filename = filename.replaceAll("\"", ".");
}
if (filename.indexOf(">") > 0) {
filename = filename.replaceAll(">", ".");
}
if (filename.indexOf("<") > 0) {
filename = filename.replaceAll("<", ".");
}
if (filename.indexOf("|") > 0) {
filename = filename.replaceAll("|", ".");
}
String filePath = fPath + "\\" + filename;
File file = new File(filePath);
if (!file.exists()) {
file.mkdir();
}
JDBCHelper helper = new JDBCHelper();
helper.insertFilePath(filename, filePath, strUrl);
GetPicture getp = new GetPicture();
getp.get(strUrl, filePath);
BufferedReader bReader = new BufferedReader(new InputStreamReader(is));
StringBuffer sb = new StringBuffer();
String rLine = null;
String tmp_rLine = null;
while ((rLine = bReader.readLine()) != null) {
tmp_rLine = rLine;
int str_len = tmp_rLine.length();
if (str_len > 0) {
sb.append("\n" + tmp_rLine);
if (deepUrls.get(strUrl) < webDepth)
getUrlByString(tmp_rLine, strUrl);
}
tmp_rLine = null;
}
is.close();
System.out.println("获取网站成功 " + strUrl);
addWebSuccessed();
} catch (Exception e) {
System.out.println("获取网站失败，请检查URL是否存在 " + strUrl);
addWebFailed();
}
}

/**
* 判断用户所提供URL是否为域名地址
*
* @return
*/
public String getDomain() {
String reg = "(?<=http\\://[a-zA-Z0-9]{0,100}[.]{0,1})[^.\\s]*?\\.(com|cn|net|org|biz|info|cc|tv|edu)";
Pattern p = Pattern.compile(reg, Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(strHomePage);
boolean blnp = m.find();
if (blnp == true) {
return m.group(0);
}
return null;
}

/**
* 解析新的网页，提取其中含有的链接信息
*
* @param inputArgs
* @param strUrl
*/
public void getUrlByString(String inputArgs, String strUrl) {
String tmpStr = inputArgs;
String regUrl = "(?<=(href=)[\"]?[\']?)[http://][^\\s\"\'\\?]*(" + myDomain + ")[^\\s\"\'>]*";
Pattern p = Pattern.compile(regUrl, Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(tmpStr);
boolean blnp = m.find();
while (blnp == true) {
if (!allUrls.containsKey(m.group(0))) {
System.out.println("Find a new url,depth:" + (deepUrls.get(strUrl) + 1) + " " + m.group(0));
arrUrls.add(m.group(0));
arrUrl.add(m.group(0));
allUrls.put(m.group(0), getIntWebIndex());
deepUrls.put(m.group(0), (deepUrls.get(strUrl) + 1));
}
tmpStr = tmpStr.substring(m.end(), tmpStr.length());
m = p.matcher(tmpStr);
blnp = m.find();
}
}

/**
* @author amuxia 另一个独立的爬取线程
*/
class Processer implements Runnable {
GetWeb gw;

public Processer(GetWeb g) {
this.gw = g;
}

public void run() {
while (!arrUrls.isEmpty()) {
String tmp = getAUrl();
getWebByUrl(tmp, allUrls.get(tmp) + "");
}
}
}
}

如图，此处添加要爬取的网址。

private String fPath = "CSDN"; 这里定义你爬取图片存放的位置，这里直接放在工程下的CSDN文件夹下，随意放，自己找得到就OK。

第三步，抓取图片下载

package org.amuxia.demo;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GetPicture {

public void getHtmlPicture(String httpUrl, String filePath) {
URL url;
BufferedInputStream in;
FileOutputStream file;

try {
System.out.println("爬取网络图片");
// 获取图片名
String fileName = httpUrl.substring(httpUrl.lastIndexOf("/")).replace("/", "");
// 初始化url对象
url = new URL(httpUrl);
// 初始化in对象，也就是获得url字节流
in = new BufferedInputStream(url.openStream());
file = new FileOutputStream(new File(filePath + "\\" + fileName));
int t;
while ((t = in.read()) != -1) {
file.write(t);
}
file.close();
in.close();
System.out.println("图片爬取成功");
} catch (Exception e) {
e.printStackTrace();
}
}

public String getHtmlCode(String httpUrl) throws IOException {
String content = "";
URL url = new URL(httpUrl);
BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
String input;
// 如果有数据
while ((input = reader.readLine()) != null) {
// 将读取数据赋给content
content += input;
}
// 关闭缓冲区
reader.close();
// 返回content
return content;
}

/**
* 图片爬取方法
*
* @param url
* @throws IOException
*/
public void get(String url, String filePath) throws IOException {

// 定义两个获取网页图片的正则表达式
String searchImgReg = "(?x)(src|SRC|background|BACKGROUND)=('|\")/?(([\\w-]+/)*([\\w-]+\\.(jpg|JPG|png|PNG|gif|GIF)))('|\")";
String searchImgReg2 = "(?x)(src|SRC|background|BACKGROUND)=('|\")(http://([\\w-]+\\.)+[\\w-]+(:[0-9]+)*(/[\\w-]+)*(/[\\w-]+\\.(jpg|JPG|png|PNG|gif|GIF)))('|\")";

String content = this.getHtmlCode(url);
Pattern pattern = Pattern.compile(searchImgReg);
Matcher matcher = pattern.matcher(content);
while (matcher.find()) {
System.out.println(matcher.group(3));
this.getHtmlPicture(url + "/" + matcher.group(3), filePath);
}
pattern = Pattern.compile(searchImgReg2);
matcher = pattern.matcher(content);
while (matcher.find()) {
System.out.println(matcher.group(3));
this.getHtmlPicture(matcher.group(3), filePath);

}

}
}

这样就完成了，看看效果如何？

控制台



各层网址命名分类的文件夹



文件夹下的图片



我们看到，已经基本实现，这里不需要额外导包，只需要导一个MySQL驱动包，当然，如果不需要插入数据到数据库，对爬取图片没有任何影响，把第一个类去掉就好。另外可能有些网站做了防爬虫可能会失败。注：爬取网站之前最好和所有者进行沟通，另外爬取非公开内容是侵权的，这里只做测试使用。