将 InputStream 写入 HttpServletResponse [英] Write an InputStream to an HttpServletResponse

问题描述

我有一个要写入 HttpServletResponse 的 InputStream.有这个方法，由于使用byte[]

I have an InputStream that I want written to a HttpServletResponse. There's this approach, which takes too long due to the use of byte[]

InputStream is = getInputStream();
int contentLength = getContentLength();

byte[] data = new byte[contentLength];
is.read(data);

//response here is the HttpServletResponse object
response.setContentLength(contentLength);
response.write(data);

我想知道在速度和效率方面什么可能是最好的方法.

I was wondering what could possibly be the best way to do it, in terms of speed and efficiency.

推荐答案

只需在块中写入，而不是先将其完全复制到 Java 的内存中.下面的基本示例将其写入 10KB 的块中.通过这种方式，您最终只会使用 10KB 的一致内存，而不是完整的内容长度.此外，最终用户将更快地开始获取部分内容.

Just write in blocks instead of copying it entirely into Java's memory first. The below basic example writes it in blocks of 10KB. This way you end up with a consistent memory usage of only 10KB instead of the complete content length. Also the enduser will start getting parts of the content much sooner.

response.setContentLength(getContentLength());
byte[] buffer = new byte[10240];

try (
    InputStream input = getInputStream();
    OutputStream output = response.getOutputStream();
) {
    for (int length = 0; (length = input.read(buffer)) > 0;) {
        output.write(buffer, 0, length);
    }
}

<小时>

就性能而言，您可以使用 NIO Channels 和一个直接分配的 ByteBuffer.在一些自定义实用程序类中创建以下实用程序/助手方法，例如Utils:

public static long stream(InputStream input, OutputStream output) throws IOException {
    try (
        ReadableByteChannel inputChannel = Channels.newChannel(input);
        WritableByteChannel outputChannel = Channels.newChannel(output);
    ) {
        ByteBuffer buffer = ByteBuffer.allocateDirect(10240);
        long size = 0;

        while (inputChannel.read(buffer) != -1) {
            buffer.flip();
            size += outputChannel.write(buffer);
            buffer.clear();
        }

        return size;
    }
}

然后你使用如下:

response.setContentLength(getContentLength());
Utils.stream(getInputStream(), response.getOutputStream());

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