OAuth call for a request token yields a 400 error

I want to obtain an Access Token is for my application using the Authorization Code it just acquired. I am using this code

DefaultHttpClient client = new DefaultHttpClient();
URI uri = new URIBuilder().setScheme("https")
        .setHost("www.linkedin.com")
        .setPath("/uas/oauth2/accessToken")
        .setParameter("grant_type", "authorization_code")
        .setParameter("code", code)
        .setParameter("redirect_uri", "http://localhost:9090/ConnectSocialMedia/callBack.jsp")
        .setParameter("client_id", CONSUMER_KEY_OPTION)
        .setParameter("client_secret", CONSUMER_SECRET_OPTION)
        .build();
HttpPost post = new HttpPost(uri);
post.setHeader("Content-Type", "application/x-www-form-urlencoded");
HttpResponse response2 = client.execute(post);
System.out.println("Final Response------------>"+response2);

But I am getting HTTP/1.1 400 Bad Request. What am I doing wrong?

Any help would be really appreciated!

Solution

You're adding the parameters to the token endpoint as query parameters in the URL but they should be passed in the POST parameters. You should use something like:

DefaultHttpClient client = new DefaultHttpClient();
URI uri = new URIBuilder().setScheme("https")
    .setHost("www.linkedin.com")
    .setPath("/uas/oauth2/accessToken")
    .build();

List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("grant_type", "authorization_code"));
nvps.add(new BasicNameValuePair("code", code));
nvps.add(new BasicNameValuePair("redirect_uri", "http://localhost:9090/ConnectSocialMedia/callBack.jsp"));
nvps.add(new BasicNameValuePair("client_id", CONSUMER_KEY_OPTION));
nvps.add(new BasicNameValuePair("client_secret", CONSUMER_SECRET_OPTION));

HttpPost post = new HttpPost(uri);
post.setEntity(new UrlEncodedFormEntity(nvps));
HttpResponse response2 = client.execute(post);
System.out.println("Final Response------------>"+response2);