How can I See the content of a MultipartForm request?

Question

I am using Apache HTTPClient 4. I am doing very normal multipart stuff like this:

val entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
entity.addPart("filename", new FileBody(new File(fileName), "application/zip").asInstanceOf[ContentBody])
entity.addPart("shared", new StringBody(sharedValue, "text/plain", Charset.forName("UTF-8")));

val post = new HttpPost(uploadUrl);
post.setEntity(entity);

I want to see the contents of the entity (or post, whatever) before I send it. However, that specific method is not implemented:

entity.getContent() // not defined for MultipartEntity

How can I see what I am posting?

Answer 1

Following would help for sure:

ByteArrayOutputStream content = new ByteArrayOutputStream();
httpEntity.writeTo(content);
logger.info("Calling "+url+" with data: "+content.toString());

The above has a fix in comparison to the first answer, there is no need to pass any parameter to ByteArrayOutputStream constructor.

Answer 2

Use the org.apache.http.entity.mime.MultipartEntity writeTo(java.io.OutputStream) method to write the content to an java.io.OutputStream, and then convert that stream to a String or byte[]:

// import java.io.ByteArrayOutputStream;
// import org.apache.http.entity.mime.MultipartEntity;
// ...
// MultipartEntity entity = ...;
// ...

ByteArrayOutputStream out = new ByteArrayOutputStream(entity.getContentLength());

// write content to stream
entity.writeTo(out);

// either convert stream to string
String string = out.toString();

// or convert stream to bytes
byte[] bytes = out.toByteArray();

Note: this only works for multipart entities small enough to be read into memory, and smaller than 2Gb which is the maximum size of a byte array in Java.