How to use HttpURLConnection to send serialized object to a Servlet from Java class?

Question

I want to send a serialized object from a Java class to a servlet where the servlet should retrieve and save the object as a file. I'm aware that I have to use HttpURLConnection to make a POST request to a servlet, but I don't know whether the below code is correct.

private static HttpURLConnection urlCon;
private static ObjectOutputStream out;

public static void main(String[] args) {

    Names names = new Names();
    names.setName("ABC");
    names.setPlace("Bangalore");
    URL url;
    try {
        url = new URL("http://localhost:6080/HttpClientSerializable/HttpPostServlet");
    try {
        out = (ObjectOutputStream) urlCon.getOutputStream();
        out.writeObject(names);
        urlCon = (HttpURLConnection) url.openConnection();
        urlCon.setRequestMethod("POST");
        urlCon.setDoOutput(true);
        out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        } catch (MalformedURLException e1) {
            e1.printStackTrace();
        }
}

And in the servlet, I have the following code:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ObjectInputStream in = new ObjectInputStream(request.getInputStream());
        try {
            names = (Names) in.readObject();

        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        in.close();
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("C:/Documents and Settings/RAGASTH/Desktop/Names"));
        out.writeObject(names);
        out.close();

    }

What should I do to make it work? Also, I want the servlet to send back the object it receives as response.

Any help would be appreciated. Thanks!

Answer 1

You would need to

• Make sure the Names class implements java.io.Serializable marker interface.

• Create an ObjectOutputStream from the servlet's outputstream as follows:

   out = new ObjectOutputStream(urlCon.getOutputStream()); 

• On the receiver side, once you read the object from the servlet's inputstream and persist in the file, write it back to the response's output stream as follows:

   out = new ObjectOutputStream(response.getOutputStream()); out.writeObject(names); out.close(); 

On the sender's side:

Names names = new Names();
names.setName("ABC");
names.setPlace("Bangalore");
URL url;
try {
    url = new URL("http://localhost:6080/HttpClientSerializable/HttpPostServlet");
    urlCon = (HttpURLConnection) url.openConnection();

    urlCon.setDoOutput(true); // to be able to write.
    urlCon.setDoInput(true); // to be able to read.

    out = new ObjectOutputStream(urlCon.getOutputStream());
    out.writeObject(names);
    out.close();

    ObjectInputStream ois = new ObjectInputStream(urlCon.getInputStream());
    names = (Names) ois.readObject();
    ois.close();
} catch (IOException e) {
    e.printStackTrace();
}
catch (MalformedURLException e1) {
    e1.printStackTrace();
}

On the receiver's side:

ObjectInputStream in = new ObjectInputStream(request.getInputStream());
try {
    names = (Names) in.readObject();
} catch (ClassNotFoundException e) {
    e.printStackTrace();
}
in.close();
ObjectOutputStream out = new ObjectOutputStream(
    new FileOutputStream("C:/Documents and Settings/RAGASTH/Desktop/Names"));
out.writeObject(names);
out.close();

ObjectOutputStream oos = new ObjectOutputStream(response.getOutputStream());
oos.writeObject(names);
oos.close();