如何提高BufferedInputStream的转换速度？-灵析社区
momo小弟对io流很陌生,请问大佬下面的代码怎么优化？图片5Mb的时候要等8sm,怎么提高加载速度？ try { URL url = new URL(imageUrl); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setRequestMethod("GET"); connection.setConnectTimeout(5000); BufferedInputStream bis = new BufferedInputStream(connection.getInputStream()); ByteArrayOutputStream baos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len; while ((len = bis.read(buffer)) != -1) { baos.write(buffer, 0, len); } OutputStream outputStream = response.getOutputStream(); response.setContentType("image/jpg"); outputStream.write(baos.toByteArray()); outputStream.flush(); outputStream.close(); } catch (Exception e) { e.printStackTrace(); }
中年复健狗你的问题主要有这么几处：
1. 从HTTP读取到的数据，等待 全部读取完放在了内存中，等待耗时，文件很大并发时可能会内存溢出
2. 阻塞读取，将数据全部存"buffer"过程中，"response"一直在等待，什么也没做，可以边读边写
3. HTTP请求连接未复用，建议使用"OK-http"等库复用连接
4. 资源未释放，"response"会等待超时，且内存会泄露
方案1：
原始流复制，这里的"buffer"越大，效率越快，但是注意内存占用
HttpURLConnection connection = null;
try {
URL url = new URL(imageUrl);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(5000);
try(InputStream bis = new BufferedInputStream(connection.getInputStream());
OutputStream out = response.getOutputStream()) {
response.setContentType("image/jpg");
// buffer 越大，效率越快
byte[] buffer = new byte[1024];
int len;
while ((len = bis.read(buffer)) != -1) {
out.write(buffer, 0, len);
out.flush();
}
}
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if(null != connection){
connection.disconnect();
}
}
方案2:
使用一些三方库的COPY工具类
HttpURLConnection connection = null;
try {
URL url = new URL(imageUrl);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(5000);
try(InputStream bis = new BufferedInputStream(connection.getInputStream());
OutputStream out = response.getOutputStream()) {
response.setContentType("image/jpg");
IoUtil.copy(bis, out);
}
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if(null != connection){
connection.disconnect();
}
}
方案3：
使用NIO非阻塞传输，同样缓冲区越大，效率越快
HttpURLConnection connection = null;
try {
URL url = new URL(imageUrl);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(5000);
try (ReadableByteChannel in = Channels.newChannel(new BufferedInputStream(connection.getInputStream()));
WritableByteChannel out = Channels.newChannel(response.getOutputStream())) {
response.setContentType("image/jpg");
ByteBuffer byteBuffer = ByteBuffer.allocate(8192);
while (in.read(byteBuffer) != -1) {
// 写转读
byteBuffer.flip();
out.write(byteBuffer);
byteBuffer.clear();
}
}
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if (null != connection) {
connection.disconnect();
}
}