Java 网络资源下载

通过Java 下载网络资源

1、通过url获取网络资源文件流

2、将文件流写入字节数组

3、将字节数组输出到客户端浏览器

4、这种方式文件名及扩展名根据URL自行定义

5、适用于图片 .xml .txt 等浏览器可直接解析的资源下载，其他资源可以直接根据URL进行下载

 

6、http client 下载方式

/**
	 * 图片另存为
	 * @param request
	 * @param response
	 */
	@RequestMapping("img_download")
	public void downloadHouseImg(HttpServletRequest request,HttpServletResponse resp){
		String url = request.getParameter("img_url");
		//获取网络图片
		InputStream content = null;
		//创建零时文件
		String timstamp = String.valueOf(System.currentTimeMillis());
		HttpClient httpclient = new DefaultHttpClient();
		Long contentLength = 0L;
		String[] fileName = url.substring(url.lastIndexOf("/") + 1).split("\\.");
		try{
		 	HttpGet httpget = new HttpGet(url);
            HttpResponse response = httpclient.execute(httpget);
            if(response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
	            HttpEntity entity = response.getEntity();
	            content = entity.getContent();
	            contentLength = entity.getContentLength();
            }
            byte[] buffer = new byte[contentLength.intValue()];
            content.read(buffer);
            // 清空response
            resp.reset();
            // 设置response的Header
            resp.addHeader("Content-Disposition", "attachment;filename=" + fileName[0]+fileName[1]);
            resp.addHeader("Content-Length", "" + buffer.length);
            resp.setContentType("application/octet-stream");
            OutputStream toClient = new BufferedOutputStream(resp.getOutputStream());
            toClient.write(buffer);
            toClient.flush();
            toClient.close();
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			httpclient.getConnectionManager().shutdown();
		}
	}

 7、进过测试  httpclient下载方式，图片会平凡出现不完整问题  提供以下流下载方法

public void downloadHouseImg(HttpServletRequest request,HttpServletResponse resp){
		String url = request.getParameter("img_url");
		String[] fileName = url.substring(url.lastIndexOf("/") + 1).split("\\.");
		//获取网络图片
		InputStream content = null;
		String timstamp = String.valueOf(System.currentTimeMillis());
		HttpClient httpclient = new DefaultHttpClient();
		Long contentLength = 0L;
		try{
			URL img = new URL(url);
			InputStream imgis = img.openStream();
            resp.reset();
            if(fileName != null && fileName.length >= 2){
            	resp.addHeader("Content-Disposition", "attachment;filename=" + fileName[0] + "." + fileName[1]);
            }else{
            	resp.addHeader("Content-Disposition", "attachment;filename=" + timstamp+".png");
            }
            resp.setContentType("application/octet-stream");
            OutputStream ots = resp.getOutputStream();
            int size = 0;
            byte[] buffer = new byte[8192];
            while((size = imgis.read(buffer)) != -1){
            	ots.write(buffer,0,size);
            }
            ots.flush();
            ots.close();
            imgis.close();
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			httpclient.getConnectionManager().shutdown();
		}
	}