stream_todd.java

package com.siddhantkushwaha.server;

import com.siddhantkushwaha.todd.GDrive;
import org.springframework.http.*;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;

import java.io.*;
import java.util.List;

@RestController
public class GDriveController {

    private static final GDrive gDrive = new GDrive();

    @GetMapping("/file/{fileId}")
    public ResponseEntity<StreamingResponseBody> func(@PathVariable String fileId, @RequestHeader() HttpHeaders requestHeaders) throws FileNotFoundException {

        long size = gDrive.getSize(fileId);
        System.out.printf("********************* Total Content Length - %s *********************", size);

        List<HttpRange> ranges = requestHeaders.getRange();
        long start = 0, end = size - 1;
        if (!ranges.isEmpty()) {
            start = ranges.get(0).getRangeStart(size);
            end = ranges.get(0).getRangeEnd(size);
        }

        System.out.printf("********************* Range: bytes=%s-%s *********************", start, end);

        InputStream inputStream = gDrive.downloadAsInputStream(fileId, start, end);

        /*
            // ***** writeFile writes data from inputSteam to outStream only when requested by client ******
            fun writeFile(ist: InputStream, fos: OutputStream) {
                // write in 2MB chunks, this can be changed
                val buffer = ByteArray(1024 * 1024 * 2)
                var bufferLength = ist.read(buffer)
                while (bufferLength > 0) {
                    println("Writing..")
                    fos.write(buffer, 0, bufferLength)
                    fos.flush()
                    bufferLength = ist.read(buffer)
                }
            }
        */
        StreamingResponseBody srb = outputStream -> Util.Companion.writeFile(inputStream, outputStream);

        HttpHeaders httpHeaders = new HttpHeaders();
        long contentLength = (end - start) + 1;
        httpHeaders.setContentLength(contentLength);
        httpHeaders.set("Content-Range", String.format("bytes %d-%d/%d", start, end, size));

        return new ResponseEntity<>(srb, httpHeaders, HttpStatus.PARTIAL_CONTENT);
    }
}