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/** 根据InputStream对应的字节数组读取InputStream长度,会将InputStream指针移动至InputStream尾,不利于后续读取,readInputStream(inputStream).length等同于inputStream.readAllBytes().length,readAllBytes从当前指针位置读取,读取后指针留在最后的位置 */
public byte[] readInputStream(InputStream inputStream) {
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int length;
try {
while ((length = inputStream.read(buffer)) != -1) {
outStream.write(buffer, 0, length);
}
} catch (IOException e) {
e.printStackTrace();
}
return outStream.toByteArray();
}
/** 一步到位方式,从InputStream指针当前位置起获取InputStream长度,且读取后不会改动InputStream指针位置,没有read指针从0开始 */
inputStream.available();
/** 扩展:从网络中读取InputStream后,可能因网络质量一次读取后InputStream长度为0,建议加入循环 */
int count = 0;
while (count == 0) {
count = inputStream.available();
}
/** 扩展:如果已知InputStream长度,InputStream指针在首部,可在当前指针位置,通过mark标记位置,参数为标记位无效前的已读字节长,已读的字节数超过此参数,标记位无效,reset也不能将指针返回此标记位,注意:已读字节长相对于mark标记位置开始,而非从InputStream的头部开始 */
inputStream.mark(count);
inputStream.reset();
/** 指针移动至当前指针1024个字节后 */
inputStream.read(new byte[1024]);
/** 更新:从网络中获取inputstream,并得到其长度时,如果网络阻塞,inputstream的available()会小于完整长度,甚至为0,推荐: */
URL url = null;
try {
url = new URL(urlString);
} catch (MalformedURLException e) {
e.printStackTrace();
}
HttpURLConnection httpURLConnection = null;
try {
httpURLConnection = (HttpURLConnection) url.openConnection();
} catch (IOException e) {
e.printStackTrace();
}
httpURLConnection.getContentLength();