import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class HttpDownload {
  public static void main(String[] args) {
    String url = "http://localhost:8081/dev/导入模板.xlsx";
    HttpDownload.download(url, "导入模板.xlsx", "D:\\");
  }

  /**
   * 根据http地址下载.
   * 
   * @param httpUrl  下载地址
   * @param fileName 文件名
   * @param savePath 保存路径
   */
  public static void download(String httpUrl, String fileName, String savePath) {
    // 转换为utf8,防止中文路径无法下载
    httpUrl = toUtf8(httpUrl);

    URL url = null;
    HttpURLConnection conn = null;
    InputStream inputStream = null;
    FileOutputStream fos = null;

    try {
      url = new URL(httpUrl);
      conn = (HttpURLConnection) url.openConnection();
      conn.setConnectTimeout(10 * 1000); // 设置超时时间为10秒
      inputStream = conn.getInputStream(); // 获得下载下来的输入流

      // 将输入流转换为字节数组
      byte[] byteData = readInputStream(inputStream);

      // 文件保存位置
      File saveDir = new File(savePath);
      if (!saveDir.exists()) {
        saveDir.mkdir();
      }

      File file = new File(saveDir + File.separator + fileName);
      fos = new FileOutputStream(file);
      fos.write(byteData);
    } catch (MalformedURLException mue) {
      mue.printStackTrace();
    } catch (FileNotFoundException fnfe) {
      fnfe.printStackTrace();
    } catch (IOException ioe) {
      ioe.printStackTrace();
    } finally {
      if (fos != null) {
        try {
          fos.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (inputStream != null) {
        try {
          inputStream.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

    System.out.println("下载完成");
  }

  /**
   * 读取输入流为字节数组.
   * 
   * @param inputStream 待读取流
   * @return
   */
  public static byte[] readInputStream(InputStream inputStream) {
    byte[] buffer = new byte[1024];
    int len = 0;
    ByteArrayOutputStream bos = new ByteArrayOutputStream();

    try {
      while ((len = inputStream.read(buffer)) != -1) {
        bos.write(buffer, 0, len);
      }
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      if (bos != null) {
        try {
          bos.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

    return bos.toByteArray();
  }

  /**
   * 转换为utf8编码.
   * 
   * @param s 待转换字符串
   * @return
   */
  public static String toUtf8(String s) {
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < s.length(); i++) {
      char c = s.charAt(i);
      if (c >= 0 && c <= 255) {
        sb.append(c);
      } else {
        byte[] b;
        try {
          b = String.valueOf(c).getBytes("utf-8");
        } catch (Exception ex) {
          System.out.println(ex);
          b = new byte[0];
        }
        for (int j = 0; j < b.length; j++) {
          int k = b[j];
          if (k < 0) {
            k += 256;
          }
          sb.append("%" + Integer.toHexString(k).toUpperCase());
        }
      }
    }
    return sb.toString();
  }
}