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Http断点下载实简单讲解

发布时间:2017-05-25 23:54:35

Http文件下载的普通模式就不多说了,断点下载与普通模式不一样的是,断点下载的头信息里面增加了一个属性
RANGE: bytes=100000-
这里RANGE代表客户端要从那个位置开始下载

而服务器返回时和普通模式不同的是:
1:多了一个属性
Content-Range=bytes 100000-19999/20000
注意还有一些属性要设置,和普通模式一样,例如Content-Length属性
2:返回码为206

java代码:

@SuppressWarnings({ "unchecked" })
@RequestMapping(value = "/downOdex.do")
public ResponseEntity<String> downFile(
		@RequestParam(value="odexName")String odexName,
		HttpServletResponse response,
		HttpServletRequest request){
		InputStream inputStream = null;
		ServletOutputStream out = null;
    	try {
        File file = new File(OdexManage.odexFileBasePath + "\\\\" + odexName);
        int fSize = Integer.parseInt(String.valueOf(file.length()));  
        response.setCharacterEncoding("utf-8");
        response.setContentType("application/x-download");  
        response.setHeader("Accept-Ranges", "bytes");  
        response.setHeader("Content-Length", String.valueOf(fSize));  
        response.setHeader("Content-Disposition", "attachment;fileName=" + odexName);
        inputStream=new FileInputStream(OdexManage.odexFileBasePath + "\\\\" + odexName);
        long pos = 0;  
        if (null != request.getHeader("Range")) {
            // 断点续传
            response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);  
            try {  
                pos = Long.parseLong(request.getHeader("Range").replaceAll("bytes=", "")
				.replaceAll("-", ""));  
            } catch (NumberFormatException e) {
                pos = 0;  
            }  
        }  
        out = response.getOutputStream();  
        String contentRange = new StringBuffer("bytes ").append(pos+"").append("-")
		.append((fSize - 1)+"").append("/").append(fSize+"").toString();
        response.setHeader("Content-Range", contentRange);  
        inputStream.skip(pos);  
        byte[] buffer = new byte[1024*10];
        int length = 0;  
        while ((length = inputStream.read(buffer, 0, buffer.length)) != -1) {  
            out.write(buffer, 0, length);
	    <span style="font-family: Consolas;">Thread.sleep(</span><code class=
        "java value">100</code><code class="java plain">);</code>
        }
	    } catch (Exception e) {
		logger.error("ODEX软件下载异常:"+e);
		}finally{
         try {
        	 if(null != out) out.flush();
        	 if(null != out) out.close();
        	 if(null != inputStream) inputStream.close(); 
		} catch (IOException e) {
		}
	}
    return new ResponseEntity(null,HttpStatus.OK);
}

 其重点在于HTTP协议里面属性有一些不同的地方,还有就是InputStream跳过不需要读的文件,和注意关闭流。

 

摘自:您到ITEYE网站看 java小强 原创,谢谢!
http://cuisuqiang.iteye.com/

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