前言：通过浏览器请求文件流进行文件下载这里就不说了，网上有很多例子，这里主要是记录一下工作中的另一个场景，一个服务器通过HTTPClient向另一个服务请求文件流，在内存中进行业务逻辑处理，并不需要下载到本地，当然，如果你想要下载本地也是可以的，把文件流写到本地磁盘就可以了，也可以写到文件系统中。废话不多说。
一，服务器传输的是普通的文件流，没有经过压缩
服务器：
@RequestMapping(value = "/getCommonFile", method = RequestMethod.POST) ???public void getFile(HttpServletResponse response) { ???????BufferedInputStream buffInputStream = null; ???????OutputStream outputStream = null; ???????try { ???????????buffInputStream = new BufferedInputStream(new FileInputStream(new File("D:\\testFile\\test.txt"))); ???????????outputStream = response.getOutputStream(); ???????????byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些 ???????????int len = 0; ???????????while((len = buffInputStream.read(buff)) > 0) { ???????????????//把文件流写入到response的输出流中，供请求端请求 ???????????????outputStream.write(buff, 0, len); ???????????????outputStream.flush(); ???????????} ???????} catch (FileNotFoundException e) { ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????if(buffInputStream != null) { ???????????????????buffInputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????????try { ???????????????if(outputStream != null) { ???????????????????outputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???}客户端：
public void getCommonFile() throws IOException { ???????//从服务器请求文件流，具体代码就不贴了 ???????CloseableHttpResponse response = HttpSender.toPost(FILE_URL, null); ???????InputStream inputStream = response.getEntity().getContent(); ???????ByteArrayOutputStream byteArray = new ByteArrayOutputStream(); ???????byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些 ???????int len = 0; ???????while((len = inputStream.read(buff)) > 0) { ???????????//把从服务端读取的文件流保存到ByteArrayOutputSteam中 ???????????byteArray.write(buff, 0, len); ???????????byteArray.flush(); ???????} ???????inputStream.close(); ???????response.close(); ???????BufferedReader bufferedReader = new BufferedReader( ???????????????new InputStreamReader(new ByteArrayInputStream(byteArray.toByteArray()), "utf-8")); ???????String line = null; ???????while((line = bufferedReader.readLine()) != null) { ???????????System.out.println(line); ???????}二，服务器传输的是压缩的文件流（直接读取的压缩文件）
@RequestMapping(value = "/getZipFile", method = RequestMethod.POST) ???public void getZipFile(HttpServletResponse response) { ???????BufferedInputStream buffInputStream = null; ???????OutputStream outputStream = null; ???????try { ???????????buffInputStream = new BufferedInputStream(new FileInputStream(new File("D:\\testFile\\test.gz"))); ???????????outputStream = response.getOutputStream(); ???????????byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些 ???????????int len = 0; ???????????while((len = buffInputStream.read(buff)) > 0) { ???????????????//把文件流写入到response的输出流中，供请求端请求 ???????????????outputStream.write(buff, 0, len); ???????????????outputStream.flush(); ???????????} ???????} catch (FileNotFoundException e) { ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????if(buffInputStream != null) { ???????????????????buffInputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????????try { ???????????????if(outputStream != null) { ???????????????????outputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???}客户端：
public void getZipFile() throws IOException { ???????//从服务器请求文件流，具体代码就不贴了 ???????CloseableHttpResponse response = HttpSender.toPost(FILE_URL, null); ???????InputStream inputStream = response.getEntity().getContent(); ???????ByteArrayOutputStream byteArray = new ByteArrayOutputStream(); ???????byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些 ???????int len = 0; ???????while((len = inputStream.read(buff)) > 0) { ???????????//把从服务端读取的文件流保存到ByteArrayOutputSteam中 ???????????byteArray.write(buff, 0, len); ???????????byteArray.flush(); ???????} ???????inputStream.close(); ???????response.close(); ???????//GZIPInputstream解压文件，然后读取文件 ???????BufferedReader bufferedReader = new BufferedReader( ???????????????new InputStreamReader(new GZIPInputStream( ???????????????????????new ByteArrayInputStream(byteArray.toByteArray())), "utf-8")); ???????String line = null; ???????while((line = bufferedReader.readLine()) != null) { ???????????System.out.println(line); ???????} ???}三，服务器传输的是压缩的文件流（直接读取的普通文件，然后在内存中将文件流进行压缩）
@RequestMapping(value = "/getCommontToZipFile", method = RequestMethod.POST) ???public void getCommontToZipFile(HttpServletRequest request, HttpServletResponse response) { ???????BufferedInputStream buffInputStream = null; ???????OutputStream outputStream = null; ???????GZIPOutputStream zipOut = null; ???????try { ???????????outputStream = response.getOutputStream(); ???????????buffInputStream = new BufferedInputStream(new FileInputStream(new File("D:\\testFile\\test.txt"))); ???????????ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); ???????????//压缩文件 ???????????zipOut = new GZIPOutputStream(byteArrayOutputStream); ???????????byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些 ???????????int len = 0; ???????????while((len = buffInputStream.read(buff)) > 0) { ???????????????//把文件流写入到byteArrayOutputStream里面 ???????????????zipOut.write(buff, 0, len); ???????????????zipOut.flush(); ???????????} ???????????outputStream.write(byteArrayOutputStream.toByteArray()); ???????} catch (FileNotFoundException e) { ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????if(buffInputStream != null) { ???????????????????buffInputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????????try { ???????????????if(outputStream != null) { ???????????????????outputStream.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????????try { ???????????????if(zipOut != null) { ???????????????????zipOut.close(); ???????????????} ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???}客户端：
和第二种情况的客户端代码一样，就 不贴代码了
四，把多个压缩文件流 写在一个byteArray中
服务端：
@RequestMapping(value = "/getMultiZipFile", method = RequestMethod.POST) ???public void getMultiZipFile(HttpServletRequest request, HttpServletResponse response) { ???????ByteArrayOutputStream byteArray = new ByteArrayOutputStream(); ???????List<File> files = new ArrayList<File>(); ???????File file = new File("D:\\testFile\\test1.gz"); ???????files.add(file); ???????file = new File("D:\\testFile\\test2.gz"); ???????files.add(file); ???????for(File file1 : files) { ???????????readDetailDataToByteArray(byteArray, file1); ???????} ???} ???public static void readDetailDataToByteArray(ByteArrayOutputStream byteArray, File file) { ???????BufferedInputStream bufferedInputStream = null; ???????try { ???????????bufferedInputStream = new BufferedInputStream(new FileInputStream(file)); ???????????byte[] b = new byte[1024*1024]; ???????????int j; ???????????while ((j = bufferedInputStream.read(b)) > 0) { ???????????????byteArray.write(b, 0, j); ???????????????byteArray.flush(); ???????????} ???????} catch (FileNotFoundException e) { ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????try { ???????????????if(bufferedInputStream != null) { ???????????????????bufferedInputStream.close(); ???????????????} ???????????} catch (Exception e) { ???????????} ???????} ???}客户端：
和第二种情况的客户端代码一样，就 不贴代码了
public void getZipFile() throws IOException {
???//从服务器请求文件流，具体代码就不贴了
CloseableHttpResponse response = HttpSender.toPost(FILE_URL, null);
???InputStream inputStream = response.getEntity().getContent();
???ByteArrayOutputStream byteArray = new ByteArrayOutputStream();
???byte[] buff = new byte[1024*1024]; //如果是稍微大的文件，这里配置的大一些
int len = 0;
???while((len = inputStream.read(buff)) > 0) {
???????//把从服务端读取的文件流保存到ByteArrayOutputSteam中
byteArray.write(buff, 0, len);
???????byteArray.flush();
???}
???inputStream.close();
???response.close();
???//GZIPInputstream解压文件，然后读取文件
BufferedReader bufferedReader = new BufferedReader(
???????????new InputStreamReader(new GZIPInputStream(
???????????????????new ByteArrayInputStream(byteArray.toByteArray())), "utf-8"));
???String line = null;
???while((line = bufferedReader.readLine()) != null) {
???????System.out.println(line);
???}
}通过httpClient请求文件流（普通文件和压缩文件）示例
原文地址：https://www.cnblogs.com/jianyong-long/p/9693061.html