java 下载网络图片保存为文件

    
    private String downloadPicture(String urlList) throws Exception {
        //文件后缀 从最后一个点开始截取
        String suffix = urlList.substring(urlList.lastIndexOf("."), urlList.length());
        String pathRoot = System.getProperty("java.io.tmpdir") + "uploadCache/";
        File file = new File(pathRoot);
        if (!file.exists()) {
            file.mkdir();
        }
        URL url;
        url = new URL(urlList);
        DataInputStream dataInputStream = new DataInputStream(url.openStream());
        String imageName = pathRoot + UUID.randomUUID().toString().replaceAll("-", "") + suffix;
        FileOutputStream fileOutputStream = new FileOutputStream(new File(imageName));
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int length;
        while ((length = dataInputStream.read(buffer)) > 0) {
            output.write(buffer, 0, length);
        }
        fileOutputStream.write(output.toByteArray());
        dataInputStream.close();
        fileOutputStream.close();
        return imageName;
    }