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Generating List<Something> from JSON with svenson

Often you’ll find yourself wanting to parse a JSON into a Java collection but want the values inside the collection to be of a specific type. Nothing easier than that.

import org.svenson.JSONParser;
…
// Getting a list containing your own type Something.
// Assume json to be a String containing the JSON dataset.
JSONParser parser = new JSONParser();
parser.addTypeHint("[]", Something.class);
List<Something> someThings = parser.parse(List.class, json);
// someThings will be a ArrayList instance by default. You can change
// that by changing the mappings for interfaces by calling
// org.svenson.JSONParser.setInterfaceMappings(Map<Class, Class>)

Parsing into a map is not much more complicated either

JSONParser jsonParser = new JSONParser();
jsonParser.addTypeHint(new RegExPathMatcher("\\.(f1|f2)"), Something.class);
Map<String,Object> someThings = jsonParser.parse(Map.class, json);

If we want to have our Something type for more than a single field, we need to setup a matcher. Here you see an example of a RegExPathMatcher that makes sure that both the keys “f1″ and “f2″ of the map we receive will be converted to Something, while all other fields are not.

If you want to convert all map properties to Something, the RegExPathMatcher would be like this

    … new RegExPathMatcher("\\..*") …

This would match every JSON path that starts with a property. If you don’t like RegularExpressions, or are on some kind of diet on them, you can also construct a more complex matcher tree from the compositable Matchers like this

JSONParser jsonParser = new JSONParser();
jsonParser.addTypeHint(new OrMatcher(
    new PrefixPathMatcher(".f1"),
    new PrefixPathMatcher(".f2")), Something.class);
Map<String,Object> someThings = jsonParser.parse(Map.class, json);

Update: Due to me fucking up both the Prefix-/Suffix- matchers as well as their tests, the last example will only really work with the current svenson trunk/future svenson 1.3.8


JsServ – Serverside Javascript and DOM emulation

I played around with some ideas about JavaScript on the server-side and came up with this little prototype. It’s a set a spring components that allow running the scripts in a website on the server side in case a user has no support for JavaScript or has disabled it.

The following diagram shows the way things work:

The parts of jsserv

The parts of jsserv

The DOMInterceptor intercepts the HTML output of other controller and initializes a dom state with it. The document itself is parsed into a DOM tree and the referenced scripts are loaded and executed. Additional patch scripts can be defined to alter the behaviour of other scripts.

The current version adds
<a class="eventHelper" href="/app/event?uuid=42">...</a>

Links around every element for which a onclick handler is registered. The links point to a DOMEvent Controller that triggers updates in the user’s DOM State.

A little example scripts implements a collapsable tree that changes the style classes of nested unordered lists. With the JsServ DOM Manipulation this works with JavaScript as well as without JavaScript on the client side.

While this code is only a rough sketch it promises a lot in terms of vastly reducing the amount of work for sites that must use javascript to get an optimal user experience but who cannot or want not to have a java-script only site. Although the link-as-click event method is rather limited, it is good enough to make a lot of DOM manipulations possible. Expressed only once in JavaScript. Running in it’s deluxe form for people with client-side JavaScript and in a basic form for people with the help of using server-side JavaScript. All is seamlessly integratable into all kinds of Controllers.

Links:

Dependencies:

Edit: code.google.com link added, update to 0.12

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