how post file and string for HttpClient?

I use blow codes,post file and string ,but response error code 500.

Uri.Builder builder = new Uri.Builder();
              builder.path(AIRQ_POST_AIRQ);
              HttpPost post = new HttpPost(builder.build().toString());

              FileEntity imageEntity=new FileEntity(null,"multipart/form-data");

              StringEntity msgEntity = new StringEntity(msg,CharEncoding.UTF_8);
              StringEntity latEntity = new StringEntity(""+lat,CharEncoding.UTF_8);
              StringEntity lonEntity = new StringEntity(""+lon,CharEncoding.UTF_8);
              StringEntity typeEntity = new StringEntity(""+type,CharEncoding.UTF_8);
              StringEntity tagidEntity = new StringEntity(""+tagid,CharEncoding.UTF_8);
              StringEntity sourceEntit开发者_开发知识库y = new StringEntity(source,CharEncoding.UTF_8);

              post.setEntity(imageEntity);
              post.setEntity(msgEntity);
              post.setEntity(latEntity);
              post.setEntity(lonEntity);
              post.setEntity(typeEntity);
              post.setEntity(tagidEntity);
              post.setEntity(sourceEntity);

              sendAirQHttpTask(post,responseHandler);

The problem is at server side. As you can see here 500 means Internal Server Error.