如何从URL读取JSON数据到XPage Java Bean

Question

I get that typically this is something better done with Client Side JavaScript. However CSJS is not ideal in this situation for other reasons.

BUT if I have a Java object inside XPages. A managed bean maybe or whatever. Is it possible to read in JSON information to the object for parsing purposes? In theory I'd want to process the data and use it in a TypeAhead for an editbox control.

The reason I'm interested in this rather then using the more tradition domino object model is the speed of getting the entries. I'm wondering if a view thats using the great "startkey" parameter is faster then something like getAllEntriesByKey().

For instance this view: http://xpagescheatsheet.com/fakenames.nsf/1fcbbeb633d9fdb3852576480057a7dc?ReadViewEntries&outputformat=JSON&StartKey=Fav

To to sum up I'm look to see if it's possible to injest the data from that link into a Java Object from XPages. the key could be anything... doesn't have to be "Fav".

Thank you!

Answer 1

There are 2 parts to the question:

1. How to read data from an URL. Here Oliver provided the hint: use the Apache HTTP client (the libraries are in XPages)

2. How to turn that JSON into a Java object. Here I would use Google GSON and a matching object. The Apache HTTP client gives you access to an input stream for the body. Something like

   SomeClass createFromJson(InputStream in) { Gson gson = new GsonBuilder().create(); SomeClass sc = gson.fromJson(in, SomeClass.class); return sc; }

Answer 2

I definitely support the way Stefan suggests - and I do that myself.

If you wrap Gson in a plugin you need to take care of security and permissions. I have just recently written an article about exactly this (with Gson as the example)

However, if you do not want to add extra libraries to your application then you can also use the built-in JSON functionality (in package: com.ibm.commons.util.io.json) to obtain the same - though not in the same elegant way.

Here is a small example:

JsonJavaFactory factory = JsonJavaFactory.instanceEx;
Object jsonObjs;
try {
    String url = "http://.....";
    jsonObjs = JsonParser.fromJson(factory, new BufferedReader(new InputStreamReader(new URL(url).openStream())));
    for (Iterator<Object> val = factory.iterateArrayValues(jsonObjs); val.hasNext();) {
        JsonJavaObject obj = (JsonJavaObject) val.next();
        Double idNum = (Double) obj.getJsonProperty("id");
        String id = Integer.toString(idNum.intValue());
        if (StringUtil.isNotEmpty(id)) {
            String name = (String) obj.getJsonProperty("name");
            // Do something with id and name...
        }
    }
} catch (JsonException e) {
    e.printStackTrace();
} catch (MalformedURLException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();

/John