最近做一個帶微信頭像的二維碼的功能，微信頭像是一個連結，所以先把微信頭像下載，臨時儲存，生成二維碼

/**
 * 檔案下載工具類
 *
 * @author zhengxinghua
 */
public class DownFileUtils {

    /**
     * 下載連結圖片，臨時儲存
     * @param urlStr  連結圖片地址
     * @param savePath  要儲存的地址
     * @return  檔案
     * @throws IOException
     */
    public static File downLoadFromUrl(String urlStr, String savePath) throws IOException {

        String fileName = System.currentTimeMillis() + ".jpg";

        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        //設定超時間為3秒
        conn.setConnectTimeout(3 * 1000);
        //防止遮蔽程式抓取而返回403錯誤
        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

        //得到輸入流
        InputStream inputStream = conn.getInputStream();
        //獲取自己陣列
        byte[] getData = readInputStream(inputStream);

        //檔案儲存位置
        File saveDir = new File(savePath);
        if (!saveDir.exists()) {
            saveDir.mkdir();
        }
        File file = new File(saveDir + File.separator + fileName);
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(getData);
        if (fos != null) {
            fos.close();
        }
        if (inputStream != null) {
            inputStream.close();
        }

        return file;
    }

    /**
     * 從輸入流中獲取位元組陣列
     *
     * @param inputStream   輸入流
     * @return  位元組陣列
     * @throws IOException
     */
    public static byte[] readInputStream(InputStream inputStream) throws IOException {
        byte[] buffer = new byte[1024];
        int len = 0;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while ((len = inputStream.read(buffer)) != -1) {
            bos.write(buffer, 0, len);
        }
        bos.close();
        return bos.toByteArray();
    }
}
 

接下來是生成二維碼，用的一個開源工具類，超級好用，還得到開源大佬的指點，特別鳴謝 http://hutool.mydoc.io/#text_319501

package com.gcyh.common.utils;

import cn.hutool.core.io.FileUtil;
import cn.hutool.extra.qrcode.QrCodeUtil;
import cn.hutool.extra.qrcode.QrConfig;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
import org.springframework.mock.web.MockMultipartFile;
import org.springframework.web.multipart.MultipartFile;

import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

/**
 *二維碼生成工具類
 */
public class QrCodeUtils {

    /**
     * 生成檔案型別的帶頭像二維碼 
     * @param urlPath  頭像連結路徑
     * @return  檔案型別
     */
     public static MultipartFile generate(String urlPath) {
        try {
            URL url = new URL(urlPath);
            URLConnection urlConnection = url.openConnection();
            HttpURLConnection connection;
            if (urlConnection instanceof HttpURLConnection) {
                connection = (HttpURLConnection) urlConnection;
            } else {
                System.out.println("請輸入 URL 地址");
                return null;
            }
            InputStream inputStream = connection.getInputStream();

            Image read = ImageIO.read(inputStream);
            Image im = read;
            System.out.println(im);
            QrConfig config = new QrConfig(300, 300);
            config.setImg(im);
            config.setErrorCorrection(ErrorCorrectionLevel.M);
            BufferedImage generate = QrCodeUtil.generate("http://www.baidu.com/", config);

            ByteArrayOutputStream bs = new ByteArrayOutputStream();
            ImageOutputStream imOut = ImageIO.createImageOutputStream(bs);

            ImageIO.write(generate, "jpg", imOut);

            InputStream is = new ByteArrayInputStream(bs.toByteArray());

            MockMultipartFile file = new MockMultipartFile("123", is);

            return file;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 測試  
     * 生成檔案型別後，再反向生成圖片，看有沒有問題
     * @param args
     */
     public static void main(String[] args) {

        try {
            URL url = new URL("http://file2.youboy.com/e/2014/8/29/81/252464s.jpg");
            URLConnection urlConnection = url.openConnection();
            HttpURLConnection connection;
            if (urlConnection instanceof HttpURLConnection) {
                connection = (HttpURLConnection) urlConnection;
            } else {
                System.out.println("請輸入 URL 地址");
                return;
            }
            InputStream inputStream = connection.getInputStream();

            Image read = ImageIO.read(inputStream);
            Image im = read;
            System.out.println(im);
            QrConfig config = new QrConfig(300, 300);
            config.setImg(im);
            config.setErrorCorrection(ErrorCorrectionLevel.M);
            BufferedImage generate = QrCodeUtil.generate("http://www.baidu.com/", config);

            ByteArrayOutputStream bs = new ByteArrayOutputStream();
            ImageOutputStream imOut = ImageIO.createImageOutputStream(bs);

            ImageIO.write(generate, "jpg", imOut);

            InputStream is = new ByteArrayInputStream(bs.toByteArray());

            MockMultipartFile file = new MockMultipartFile("123", is);
            InputStream fileInputStream = file.getInputStream();
            FileUtil.writeFromStream(fileInputStream,FileUtil.file("d:/qrco33de.jpg"));

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

    }

}