RESPONDING TO FORMS - HTTP Programming Recipes for Java Bots - page 252

+ boundary);
An OutputStream object is obtained and we construct a new FormUtility
object. Notice that a boundary is specified on the constructor to the FormUtility ob-
ject. This tells the FormUtility object that this is going to be a multipart response.
Additionally, the user id and password are added to the form. The names “uid” and “pwd”
are the names of the <input> tags that the user would normally enter their user id and
password into.
OutputStream os = http.getOutputStream();
// Construct a form.
FormUtility form = new FormUtility(os, boundary);
form.add("uid", uid);
form.add("pwd", pwd);
Next, the actual file is added to the form. This version of the add method of the
FormUtility class takes care of all that is necessary to transmit the file. Finally, the
complete method is called to complete building the form.
form.add("uploadedfile", file);
form.complete();
Next, the InputStream is obtained and the request is transmitted. The
InputStream object is immediately closed; we do not care about the response from the
upload page.
// Perform the upload.
InputStream is = http.getInputStream();
is.close();
This recipe can be adapted to any case where you need to upload a file. The
FormUtility class, used by this recipe, is a short utility class that was introduced ear-
lier in this chapter.
Summary
Forms are a very common part of many web sites. Most bot programs will have to deal
with forms. Forms can be transmitted to the web server in three ways: HTTP GET , HTTP
POST and multipart POST .
A form can be sent back to the web server using the HTTP GET method. HTTP GET
places all of the name-value pairs from the form's data onto the URL. When a web site uses
HTTP GET for a form, the user can see all of their input on the URL line of the browser.
A form can also be sent back to the web server using the HTTP POST method. HTTP
POST sends the data as part of the HTTP packet, and it is not visible to the user. Because
the data does not all need to fit onto a URL, much larger amounts of data can be sent with
HTTP POST .