How to "capture" Webservice (XML) data in Java SE?

Question

I am a layman in the subject webservice and need to capture the data of a webservice that returns some little information.

The webservice is this: http://www.geoplugin.net/extras/location.gp?lat=-27.8161100&long=-50.3261100&format=xml

I found a lot of information on the internet but only for Java EE and in very complex ways.

Answer 1

You’ll need to focus in two ways which I will describe soon. From what I understand you want to make a request to a URL and get and interpret the answer, which in this case is the XML you showed. Also, you want to do this in Java.

I’m starting from the assumption that you still have nothing to do this task, so I’m going to split the answer into two parts: Requesting the URL and Reading and interpreting the response XML.

Making a request in Java

To get XML you will need to make a request for the URL http://www.geoplugin.net/extras/location.gp passing three parameters via GET. The parameters are:

• lat;
• long;
• format;

Passing the parameters and making the request, you will get the answer. The code snippet below shows how to make the request in Java:

private String fazRequest() throws IOException {
    String latitude = "-27.8161100";
    String longitude = "-50.3261100";
    String format = "xml";
    URL url = new URL("http://www.geoplugin.net/extras/location.gp");

    StringBuilder urlParametros = new StringBuilder();
    urlParametros.append("lat=").append(latitude);
    urlParametros.append("&long=").append(longitude);
    urlParametros.append("&format=").append(format);

    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.setDoOutput(true);
    DataOutputStream wr = new DataOutputStream(conn.getOutputStream());
    wr.writeBytes(urlParametros.toString());
    wr.flush();
    wr.close();

    BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String inputLine;
    StringBuilder response = new StringBuilder();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();

    return response.toString();
}

I leave the task of understanding all the above code to you. But basically, it makes a GET request to the URL by passing the necessary parameters to get the answer. The answer is read, converted to String and returned by the method.

Making the parse of XML

With the answer obtained by the previous method, we now need to interpret (parse) this answer. For this, we will use the GIFT to read and get the texts that are in XML. See below how to do this:

private void parseXML(String xml) throws ParserConfigurationException, SAXException, IOException {
    InputSource is = new InputSource(new StringReader(xml));
    DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
    Document doc = dBuilder.parse(is);
    
    doc.getDocumentElement().normalize();
    String lugar = doc.getElementsByTagName("geoplugin_place").item(0).getTextContent();
    System.out.println(lugar);
    
    String regiao = doc.getElementsByTagName("geoplugin_region").item(0).getTextContent();
    System.out.println(regiao);
    
    String pais = doc.getElementsByTagName("geoplugin_countryCode").item(0).getTextContent();
    System.out.println(pais);
}

I also leave the code above for you to study its details. What is important to know is how the XML structure works (including tag repetition) so you can develop more robust code.

Concluding...

The codes above were made only as an educational example. I didn’t care about validations, exception handling or other scenarios that XML might contain. I just made a snippet of code specifically for your problem and for you to understand how Java meets what you asked for.

Below are some links that can help in your journey:

• Reading XML Data into a DOM;
• Making requests froms Java;

Answer 2

Daew Giovani Raci Paganini checks the webservice consumption explained by Caelum also this one from netbeansClient 1: Java Class in Java SE Application. Good learning!!!