//application.properties中设置:(file.path=static/qrfile/)
//保存到static文件夹下的qrfile目录
@Value("${file.path}")
private String path;

//文件路径
String path = System.getProperty("java.class.path");
int firstIndex = path.lastIndexOf(System.getProperty("path.separator")) + 1;
int lastIndex = path.lastIndexOf(File.separator) + 1;
path = path.substring(firstIndex, lastIndex) + this.path+pathId;
path = URLDecoder.decode(path, "utf-8");

//在相应路径下创建文件,若没有此目录或文件自动创建
File outputFile = new File(path+".png");
if (!outputFile.exists()) {
    outputFile.createNewFile();
}

//文件写入
FileOutputStream out = new FileOutputStream(filePath + fileName);
out.write(file);
out.flush();
out.close();