java下载网络文件的N种方式
通过java api下载网络文件的方法有很多，主要方式有以下几种：
1、使用 common-io库下载文件，需要引入commons-io-2.6.jar
public static void downloadByCommonIO(String url, String saveDir, String fileName) {
try {
FileUtils.copyURLToFile(new URL(url), new File(saveDir, fileName));
} catch (IOException e) {
e.printStackTrace();
}
}
2、使用NIO下载文件，需要 jdk 1.4+
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();
}
}
}
}
3、使用NIO下载文件，需要 jdk 1.7+
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();
}
}
4、使用传统io stream下载文件
public static void downloadByIO(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();
}
}
}
}
5、使用Byte Array获得stream下载文件
public static void downLoadFromUrl(String urlStr,String fileName,String savePath) throws IOException{
URL url = new URL(urlStr);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
// 设置超时间为5秒
conn.setConnectTimeout(5*1000);
// 防止屏蔽程序抓取而返回403错误
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
// 得到输入流
InputStream input = conn.getInputStream();
// 获取自己数组
byte[] getData = readInputStream(input);
// 文件保存位置
File saveDir = new File(savePath);
if(!saveDir.exists()){
saveDir.mkdir();
}
File file = new File(saveDir+File.separator+fileName);
FileOutputStream output = new FileOutputStream(file);
output.write(getData);
if(output!=null){
output.close();
}
if(input!=null){
input.close();
}
System.out.println("download success!!");
}
public static byte[] readInputStream(InputStream inputStream) throws IOException {
byte[] buffer = new byte[10240];
int len = 0;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
while((len = inputStream.read(buffer)) != -1) {
bos.write(buffer, 0, len);
}
bos.close();
return bos.toByteArray();
}
转载自：java下载网络文件的N种方式 - Jaywen - 博客园 (cnblogs.com)