java代码：

引用包：

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;
import java.util.Hashtable;
import javax.imageio.ImageIO;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import sun.misc.BASE64Encoder;

方法：

/**
* 二维码生成器
*
* @param text 二维码内容
* @throws IOException
*/
@SuppressWarnings({ "unchecked", "rawtypes", "restriction" })
public static String generalQRCode(String url) { 
Hashtable hints= new Hashtable(); 
hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); 
String binary = null;

try {
BitMatrix bitMatrix = new MultiFormatWriter().encode(
url, BarcodeFormat.QR_CODE, 200, 200, hints);

// 实现一： 输出图片到指定目录
// File outputFile = new File("d://1.jpg");
// MatrixToImageWriter.writeToFile(bitMatrix, "png", outputFile);

// 实现二：生成二维码图片并将图片转为二进制传递给前台
// 1、读取文件转换为字节数组
ByteArrayOutputStream out = new ByteArrayOutputStream();
BufferedImage image = toBufferedImage(bitMatrix);
//// 
ImageIO.write(image, "png", out);
byte[] bytes = out.toByteArray();

// 2、将字节数组转为二进制
BASE64Encoder encoder = new BASE64Encoder();
binary = encoder.encodeBuffer(bytes).trim();

} catch (Exception e) {
e.printStackTrace();
}

return binary;
}

// 其他调用方法

public static BufferedImage toBufferedImage(BitMatrix matrix) {
int width = matrix.getWidth();
int height = matrix.getHeight();
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
image.setRGB(x, y, matrix.get(x, y) ? 0xFF000000 : 0xFFFFFFFF);
}
}

return image;
}

前台ajax方法：

$.ajax({
url: 方法url,
type:'post',
success : function(data) {
$('#img').attr('src', 'data:image/jpg;base64,' + data);
}
});

注意：img 的src前面需要拼接data:image/jpg;base64, 在加上后台生成的二进制才能正确解析二进制