(Java) Download File from Dropbox (Streaming)

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Downloads a file from Dropbox, streaming it directly to a file in the filesystem.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris Java Libs for Android

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // A Dropbox access token should have been previously obtained.
    // Dropbox access tokens do not expire.
    // See Dropbox Access Token.

    CkRest rest = new CkRest();

    // Connect to Dropbox
    boolean success = rest.Connect("content.dropboxapi.com",443,true,true);
    if (success != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    // Add request headers.
    rest.AddHeader("Authorization","Bearer DROPBOX_ACCESS_TOKEN");

    // The download "parameters" are contained in JSON passed in an HTTP request header.
    // This is the JSON indicating the file to be downloaded:
    // { 
    //    "path": "/Homework/lit/hamlet.xml",
    // }

    CkJsonObject json = new CkJsonObject();
    json.AppendString("path","/Homework/lit/hamlet.xml");
    rest.AddHeader("Dropbox-API-Arg",json.emit());

    // Setup a file stream for the download
    CkStream fileStream = new CkStream();
    fileStream.put_SinkFile("qa_output/hamletFromDropbox.xml");

    // Indicate that the call to FullRequestNoBody should send the response body
    // to fileStream if the response status code is 200.
    // If a non-success response status code is received, then nothing
    // is streamed to the output file and the error response is returned by FullRequestNoBody.
    int expectedStatus = 200;
    rest.SetResponseBodyStream(expectedStatus,true,fileStream);

    String responseStr = rest.fullRequestNoBody("POST","/2/files/download");
    if (rest.get_LastMethodSuccess() != true) {
        System.out.println(rest.lastErrorText());
        return;
        }

    // When successful, Dropbox responds with a 200 response code.
    if (rest.get_ResponseStatusCode() != 200) {
        // Examine the request/response to see what happened.
        System.out.println("response status code = " + rest.get_ResponseStatusCode());
        System.out.println("response status text = " + rest.responseStatusText());
        System.out.println("response header: " + rest.responseHeader());
        System.out.println("response body (if any): " + responseStr);
        System.out.println("---");
        System.out.println("LastRequestStartLine: " + rest.lastRequestStartLine());
        System.out.println("LastRequestHeader: " + rest.lastRequestHeader());
        return;
        }

    // Information about the downloaded file is also available as JSON in a response header.
    // The "dropbox-api-result" response header contains the information.  For example:
    String apiResult = rest.responseHdrByName("dropbox-api-result");
    System.out.println(apiResult);

    // In this case, the pretty-formatted dropbox-api-result JSON looks like this:
    // { 
    //   "name": "hamlet.xml",
    //   "path_lower": "/homework/lit/hamlet.xml",
    //   "path_display": "/Homework/lit/hamlet.xml",
    //   "id": "id:74FkdeNuyKAAAAAAAAAAAQ",
    //   "client_modified": "2016-06-02T23:19:00Z",
    //   "server_modified": "2016-06-02T23:19:00Z",
    //   "rev": "9482db15f",
    //   "size": 279658
    // }

    // Load the JSON, pretty-print it, and demonstrate how to get some values...
    CkJsonObject jsonResult = new CkJsonObject();
    jsonResult.put_EmitCompact(false);
    jsonResult.Load(apiResult);
    // Show the JSON pretty-printed...
    System.out.println(jsonResult.emit());

    // Sample code to get data from the JSON response:
    int size = jsonResult.IntOf("size");
    System.out.println("size = " + size);

    String rev = jsonResult.stringOf("rev");
    System.out.println("rev = " + rev);

    String clientModified = jsonResult.stringOf("client_modified");
    CkDateTime ckdt = new CkDateTime();
    ckdt.SetFromTimestamp(clientModified);
    boolean bLocalTime = true;
    CkDtObj dt = ckdt.GetDtObj(bLocalTime);
    System.out.println(dt.get_Day() + "/" + dt.get_Month() + "/" + dt.get_Year() + " " + dt.get_Hour() + ":"
         + dt.get_Minute());
  }
}