FileUtils

import org.apache.commons.io.IOUtils;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.util.Base64;
import static org.apache.commons.io.FileUtils.openOutputStream;
public class FileUtils {
  /**
   * 创建临时文件.
   *
   * @param inputStream
   *            输入文件流
   * @param name
   *            文件名
   * @param ext
   *            扩展名
   * @param tmpDirFile
   *            临时文件夹目录
   */
  public static File createTmpFile(InputStream inputStream, String name, String ext, File tmpDirFile)
      throws IOException {
    File resultFile = File.createTempFile(name, '.' + ext, tmpDirFile);
    resultFile.deleteOnExit();
    copyToFile(inputStream, resultFile);
    return resultFile;
  }
  private static void copyToFile(final InputStream source, final File destination) throws IOException {
    try (InputStream in = source; OutputStream out = openOutputStream(destination)) {
      IOUtils.copy(in, out);
    }
  }
  /**
   * 创建临时文件.
   *
   * @param inputStream
   *            输入文件流
   * @param name
   *            文件名
   * @param ext
   *            扩展名
   */
  public static File createTmpFile(InputStream inputStream, String name, String ext) throws IOException {
    return createTmpFile(inputStream, name, ext, Files.createTempDirectory("weixin-java-tools-temp").toFile());
  }
  /**
   * 文件流生成base64
   *
   * @param in
   *            文件流
   * @return base64编码
   */
  public static String imageToBase64ByStream(InputStream in) {
    byte[] data = null;
    // 读取图片字节数组
    try {
      data = new byte[in.available()];
      in.read(data);
      // 返回Base64编码过的字节数组字符串
      return Base64.getEncoder().encodeToString(data);
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      if (in != null) {
        try {
          in.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
    return null;
  }
}