Java 从网上下载文件的几种方式实例代码详解

废话不多说了，直接给大家贴代码了，具体代码如下所示；

package com.github.pandafang.tool;
import java.io.bufferedoutputstream;
import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.net.url;
import java.nio.channels.channels;
import java.nio.channels.filechannel;
import java.nio.channels.readablebytechannel;
import java.nio.file.files;
import java.nio.file.path;
import java.nio.file.paths;
import java.nio.file.standardcopyoption;
import org.apache.commons.io.fileutils;
/**
 * 文件工具类
 * @author panda fang
 * @date 2017-08-26
 * @version 1.0
 */
public class filetool {
  /**
   * 使用传统io stream 下载文件
   * @param url
   * @param savedir
   * @param filename
   */
  public static void download(string url, string savedir, string filename) {
    bufferedoutputstream bos = null;
    inputstream is = null;
    try {
      byte[] buff = new byte[8192];
      is = new url(url).openstream();
      file file = new file(savedir, filename);
      file.getparentfile().mkdirs();
      bos = new bufferedoutputstream(new fileoutputstream(file));
      int count = 0;
      while ( (count = is.read(buff)) != -1) {
        bos.write(buff, 0, count);
      }
    }
    catch (ioexception e) {
      e.printstacktrace();
    }
    finally {
      if (is != null) {
        try {
          is.close();
        } catch (ioexception e) {
          e.printstacktrace();
        }
      }
      if (bos != null) {
        try {
          bos.close();
        } catch (ioexception e) {
          e.printstacktrace();
        }
      }
    }
  }
  /**
   * 利用 commonio 库下载文件，依赖apache common io ，官网 https://commons.apache.org/proper/commons-io/
   * @param url
   * @param savedir
   * @param filename
   */
  public static void downloadbyapachecommonio(string url, string savedir, string filename) {
    try {
      fileutils.copyurltofile(new url(url), new file(savedir, filename));
    } catch (ioexception e) {
      e.printstacktrace();
    }
  }
  /**
   * 使用nio下载文件， 需要 jdk 1.4+
   * @param url
   * @param savedir
   * @param filename
   */
  public static void downloadbynio(string url, string savedir, string filename) {
    readablebytechannel rbc = null;
    fileoutputstream fos = null;
    filechannel foutc = null;
    try {
      rbc = channels.newchannel(new url(url).openstream());
      file file = new file(savedir, filename);
      file.getparentfile().mkdirs();
      fos = new fileoutputstream(file);
      foutc = fos.getchannel();
      foutc.transferfrom(rbc, 0, long.max_value);
    } catch (ioexception e) {
      e.printstacktrace();
    } finally {
      if (rbc != null) {
        try {
          rbc.close();
        } catch (ioexception e) {
          e.printstacktrace();
        }
      }
      if (foutc != null) {
        try {
          foutc.close();
        } catch (ioexception e) {
          e.printstacktrace();
        }
      }
    }
  }
  /**
   * 使用nio下载文件， 需要 jdk 1.7+
   * @param url
   * @param savedir
   * @param filename
   */
  public static void downloadbynio2(string url, string savedir, string filename) {
    try (inputstream ins = new url(url).openstream()) {
      path target = paths.get(savedir, filename);
      files.createdirectories(target.getparent());
      files.copy(ins, target, standardcopyoption.replace_existing);
    } catch (ioexception e) {
      e.printstacktrace();
    } 
  }
}

下载一个百度logo 测试一下

 public static void main(string[] args) {
    filetool.downloadbynio2("http://www.baidu.com/img/bd_logo1.png", "/home/panda/picture", "baidu_logo.png");
    system.out.println("done...");
  }

总结

以上所述是小编给大家介绍的java 从网上下载文件的几种方式实例代码详解，希望对大家有所帮助