java InputStream 复制

tika 是一个解析文档的工具箱，可以自己判别文档种类，再用合适的jar包 解析对应的文档

今天遇到一个需求，把网络上的文件内容解析成数据。

写爬虫，解析页面，对页面进行处理，解析出文件的url

接着就是文件下载到本地，对照tika 的demo 解析数据

可是文件下载到本地占用硬盘空间不说还会消耗磁盘io

既然需要数据只要在内存中处理就好了

使用

inputStream in =response.getEntity

用Tika 解析文件属性和正文，但是tika 分两步解析数据，任何一步都会改变inputStream

解决办法一：

inputStream的复制

ByteArrayOutputStream baos = new ByteArrayOutputStream();

		// Fake code simulating the copy
		// You can generally do better with nio if you need...
		// And please, unlike me, do something about the Exceptions :D
		byte[] buffer = new byte[1024];
		int len;
		while ((len = entity.read(buffer)) > -1 ) {
		    baos.write(buffer, 0, len);
		}
		baos.flush();

		// Open new InputStreams using the recorded bytes
		// Can be repeated as many times as you wish
		InputStream is1 = new ByteArrayInputStream(baos.toByteArray()); 
		InputStream is2 = new ByteArrayInputStream(baos.toByteArray());

第二种：包装inputStream 防止被关闭

InputStream is = null; is = getStream(); //obtain the stream CloseShieldInputStream csis = new CloseShieldInputStream(is); // call the bad function that does things it shouldn't badFunction(csis); // happiness follows: do something with the original input stream is.read();