利用java抓取網頁上的所有圖片：

用兩個正則表示式：

1、匹配html中img標籤的正則：<img.*src=(.*?)[^>]*?>

2、匹配img標籤中得src中http路徑的正則：http:\"?(.*?)(\"|>|\\s+)

實現：

package org.swinglife.main;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/***
 * java抓取網路圖片
 * @author swinglife
 *
 */
public class CatchImage {

	// 地址
	private static final String URL = "http://www.csdn.net";
	// 編碼
	private static final String ECODING = "UTF-8";
	// 獲取img標籤正則
	private static final String IMGURL_REG = "<img.*src=(.*?)[^>]*?>";
	// 獲取src路徑的正則
	private static final String IMGSRC_REG = "http:\"?(.*?)(\"|>|\\s+)";

	
	public static void main(String[] args) throws Exception {
		CatchImage cm = new CatchImage();
		//獲得html文字內容
		String HTML = cm.getHTML(URL);
		//獲取圖片標籤
		List<String> imgUrl = cm.getImageUrl(HTML);
		//獲取圖片src地址
		List<String> imgSrc = cm.getImageSrc(imgUrl);
		//下載圖片
		cm.Download(imgSrc);
	}
	
	
	/***
	 * 獲取HTML內容
	 * 
	 * @param url
	 * @return
	 * @throws Exception
	 */
	private String getHTML(String url) throws Exception {
		URL uri = new URL(url);
		URLConnection connection = uri.openConnection();
		InputStream in = connection.getInputStream();
		byte[] buf = new byte[1024];
		int length = 0;
		StringBuffer sb = new StringBuffer();
		while ((length = in.read(buf, 0, buf.length)) > 0) {
			sb.append(new String(buf, ECODING));
		}
		in.close();
		return sb.toString();
	}

	/***
	 * 獲取ImageUrl地址
	 * 
	 * @param HTML
	 * @return
	 */
	private List<String> getImageUrl(String HTML) {
		Matcher matcher = Pattern.compile(IMGURL_REG).matcher(HTML);
		List<String> listImgUrl = new ArrayList<String>();
		while (matcher.find()) {
			listImgUrl.add(matcher.group());
		}
		return listImgUrl;
	}

	/***
	 * 獲取ImageSrc地址
	 * 
	 * @param listImageUrl
	 * @return
	 */
	private List<String> getImageSrc(List<String> listImageUrl) {
		List<String> listImgSrc = new ArrayList<String>();
		for (String image : listImageUrl) {
			Matcher matcher = Pattern.compile(IMGSRC_REG).matcher(image);
			while (matcher.find()) {
				listImgSrc.add(matcher.group().substring(0, matcher.group().length() - 1));
			}
		}
		return listImgSrc;
	}

	/***
	 * 下載圖片
	 * 
	 * @param listImgSrc
	 */
	private void Download(List<String> listImgSrc) {
		try {
			for (String url : listImgSrc) {
				String imageName = url.substring(url.lastIndexOf("/") + 1, url.length());
				URL uri = new URL(url);
				InputStream in = uri.openStream();
				FileOutputStream fo = new FileOutputStream(new File(imageName));
				byte[] buf = new byte[1024];
				int length = 0;
				System.out.println("開始下載:" + url);
				while ((length = in.read(buf, 0, buf.length)) != -1) {
					fo.write(buf, 0, length);
				}
				in.close();
				fo.close();
				System.out.println(imageName + "下載完成");
			}
		} catch (Exception e) {
			System.out.println("下載失敗");
		}
	}

	
}