I use Groovy a lot. It’s simple and easy to use, runs on JVM and saves me from Java verbosity. I also like the fact that it’s dynamic.
I use it with a simple Servlet to return data to JavaScript AJAX requests. I like to keep the server side very simple, so I don’t create a lot of POJOs and I’m using HashMaps instead. Groovy has few convenient methods that makes it easy to work with Maps.
I do convert the maps into JSON when returning results to a browser. I don’t use anything fancy, just a couple lines of Groovy code to do that.
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| class JsonMap { | |
| def toJSON(elements, depth = 0) { | |
| def json = "" | |
| depth.times { json += "\t" } | |
| json += "{" | |
| elements.each { key, value -> | |
| json += "\"$key\":" | |
| json += jsonValue(value, depth) | |
| json += ", " | |
| } | |
| json = (elements.size() > 0) ? json.substring(0, json.length() - 2) : json | |
| json += "}" | |
| json | |
| } | |
| private def jsonValue(element, depth) { | |
| if (element instanceof Map) { | |
| return "\n" + toJSON(element, depth + 1) | |
| } | |
| if (element instanceof List) { | |
| def list = "[" | |
| element.each { elementFromList -> | |
| list += jsonValue(elementFromList, depth) | |
| list += ", " | |
| } | |
| list = (element.size() > 0) ? list.substring(0, list.length() - 2) : list | |
| list += "]" | |
| return list | |
| } | |
| (element instanceof String) ? "\"$element\"": element?.toString() | |
| } | |
| } | |
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| class MapToJsonTests extends GroovyTestCase { | |
| private final def mapper = new JsonMap() | |
| void test_convertMapWithListsOfMapsIntoJSON() { | |
| def map = ["a": "a", "b": [["b": "a"], 'd', [12, 12, "e"], ["r": 12]]] | |
| def expected = '''{"a":"a", "b":[ | |
| \t{"b":"a"}, "d", ["12", "12", "e"], | |
| \t{"r":"12"}]}''' | |
| def result = mapper.toJSON(map) | |
| assert expected == result | |
| } | |
| } |
With this code there is quite a bit of assumptions though:
- it will only work for Map
- it assumes Strings are used as Map Keys
- it will convert Maps, Lists and Objects
- when it meets Object it will call .toString() on it to get it’s value
- it will try to format it with tabs and new lines a bit, so it’s more pleasant for the eye and human readable
Hope it would be useful for you. Greg
Greg Gigon's wEbLOG 