二維碼，又叫二維條碼。

1.java這邊的話生成二維碼有很多開發的jar包如 zxing,qrcode ，下面是使用zxing的開發包來實現的。
ZXing專案是google code上面提供的一個關於條碼編解碼的開源專案。 
2.先下載zxing開發包，這裡用到的只是core的jar包

我在專案中使用的core2.2.jar包。

下載地址：http://download.csdn.net/download/tvcctv27tv/6841023

注：網上下載的core.jar使用JDK1.5；core2*.jar包使用JDK1.6；core3*.jar使用JDK1.7;

3. 原始碼

package com.test.qrcodes;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Hashtable;

import javax.imageio.ImageIO;

import junit.framework.Assert;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang.StringUtils;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;


public class TestQRCodes {

	private static final boolean NEEDCOMPRESS = false;

	private static String LOGO_URL;
	// LOGO寬度
	private static final int WIDTH = 60;
	// LOGO高度
	private static final int HEIGHT = 60;

	static{
		LOGO_URL = "";// 測試圖片路徑地址
	}

	/**
	 * 生成二維碼的工具類
	 * 
	 * @param data
	 *            二維碼中攜帶的資料
	 * @param width
	 *            二維碼的寬度
	 * @param height
	 *            二維碼的高度
	 * @return 返回base64格式的圖片（data:image/gif;base64,xxxx） <br>
	 *         eg： <code>
	 * <img alt="" src="data:image/gif;base64,xxxx">
	 * </code>
	 */
	public static String createQRCode(String data, int width, int height, String isPicture) {

		Assert.assertTrue("param data cannot empty.", data != null && data.trim().length() > 0);

		Assert.assertTrue("param width and height must gt 0.", width > 0 && height > 0);

		ByteArrayOutputStream bos = null;

		MultiFormatWriter formatWriter = new MultiFormatWriter();

		Hashtable<EncodeHintType, Object> param = new Hashtable<EncodeHintType, Object>();
		param.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.Q);
		param.put(EncodeHintType.CHARACTER_SET, "utf-8");
		param.put(EncodeHintType.MARGIN, 0);

		try{
			BitMatrix bitMatrix = formatWriter
					.encode(data, BarcodeFormat.QR_CODE, width, height, param);
			// 1.1去白邊
			int[] rec = bitMatrix.getEnclosingRectangle();
			int resWidth = rec[2] + 1;
			int resHeight = rec[3] + 1;
			BitMatrix resMatrix = new BitMatrix(resWidth, resHeight);
			resMatrix.clear();
			for (int i = 0; i < resWidth; i++){
				for (int j = 0; j < resHeight; j++){
					if (bitMatrix.get(i + rec[0], j + rec[1])){
						resMatrix.set(i, j);
					}
				}
			}
			int width1 = resMatrix.getWidth();
			int height1 = resMatrix.getHeight();
			BufferedImage qrcode = new BufferedImage(width1, height1, BufferedImage.TYPE_INT_RGB);
			for (int x = 0; x < width1; x++){
				for (int y = 0; y < height1; y++){
					qrcode.setRGB(x, y, resMatrix.get(x, y) == true ? Color.BLACK.getRGB() : Color.WHITE
							.getRGB());
				}
			}
			// 新增logo圖片
			if (StringUtils.isNotEmpty(LOGO_URL) && StringUtils.isNotEmpty(isPicture)){
				insertImage(width1, qrcode, LOGO_URL, NEEDCOMPRESS);
			}
			bos = new ByteArrayOutputStream();
			ImageIO.write(qrcode, "png", bos);

			String img = StringUtils.deleteWhitespace(Base64.encodeBase64String(bos.toByteArray()));
			return String.format("data:image/png;base64,%s", img);
		} catch (Exception e){
			throw new RuntimeException(e);
		} finally{
			if (bos != null){
				try{
					bos.close();
				} catch (IOException e){
				}
			}
		}

	}

	private static void insertImage(int QRCODE_SIZE, BufferedImage source, String imgPath,
			boolean needCompress) throws Exception {
		File file = new File(imgPath);
		if (!file.exists()){
			System.err.println("" + imgPath + "   該檔案不存在！");
			return;
		}
		Image src = ImageIO.read(new File(imgPath));
		int width = src.getWidth(null);
		int height = src.getHeight(null);
		if (needCompress){ // 壓縮LOGO
			if (width > WIDTH){
				width = WIDTH;
			}
			if (height > HEIGHT){
				height = HEIGHT;
			}
			Image image = src.getScaledInstance(width, height, Image.SCALE_SMOOTH);
			BufferedImage tag = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
			Graphics g = tag.getGraphics();
			g.drawImage(image, 0, 0, null); // 繪製縮小後的圖
			g.dispose();
			src = image;
		}
		// 插入LOGO
		Graphics2D graph = source.createGraphics();
		int x = (QRCODE_SIZE - width) / 2;
		int y = (QRCODE_SIZE - height) / 2;
		graph.drawImage(src, x, y, width, height, null);
		// Shape shape = new RoundRectangle2D.Float(x, y, width, width, 6, 6);
		graph.setStroke(new BasicStroke(3f));
		// graph.draw(shape); 去除圖片白邊
		graph.dispose();
	}

	/**
	 * @param data
	 *            二維碼攜帶的資料
	 * @param size
	 *            二維碼的寬、高
	 * @return
	 * @see WechatValidateUtils#generateQRCode(String, int, int)
	 */
	public static String createQRCode(String data, int size, String isPicture) {
		return createQRCode(data, size, size, isPicture);
	}

	// 測試
	public static void main(String[] args) throws Exception {
		// 生成二維碼
		String url = "http://www.sina.com.cn";
		String src = createQRCode(url, 200, "1");
		System.out.println(url.length());
		String html = "<img src=\"" + src + "\">";
		FileOutputStream ops = new FileOutputStream("D:\\QRCodeImage\\test.html");
		org.apache.commons.io.IOUtils.write(html, ops, "utf-8");
		ops.close();
	}
}