How to convert json array to java hashmap using jackson

Question

I want to convert below json array to java hashmap using jackson and iterate the values like below:

Need output like this:

key  Value 
1    sql
2    android
3    mvc

JSON Sample: enter code here

{
    "menu": [
        {
            "1": "sql",
            "2": "android",
            "3": "mvc"
        }
    ]
}

It would be really appreciated if someone can share the code to achieve this.

Thanks for your help!

What if there are two elements in the array? A JSON array is not convertible to a HashMap. — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Mar 15, 2015 at 21:13

Stephen L. · Accepted Answer · 2015-03-15 21:35:23Z

2

Here is a solution that reveals the idea:

public class JacksonSerializer {

    public static final String INPUT = "{\n" +
            "    \"menu\": [\n" +
            "        {\n" +
            "            \"1\": \"sql\",\n" +
            "            \"2\": \"android\",\n" +
            "            \"3\": \"mvc\"\n" +
            "        }\n" +
            "    ]\n" +
            "}";

    public static class MenuItems {

        Map<String, String> menu = Maps.newHashMap();
    }


    public static class MenuItemsDeserializer extends JsonDeserializer<MenuItems> {


        @Override
        public MenuItems deserialize(org.codehaus.jackson.JsonParser jsonParser,
                                               DeserializationContext deserializationContext)
                throws IOException, JsonProcessingException {

            JsonNode node = jsonParser.getCodec().readTree(jsonParser);

            final JsonNode elems = node.getElements().next().getElements().next();
            final Map<String, String> map = Maps.newHashMap();
            final Iterator<Map.Entry<String, JsonNode>> it = elems.getFields();
            while (it.hasNext()) {
                final Map.Entry<String, JsonNode> entry = it.next();
                map.put(entry.getKey(), entry.getValue().asText());
            }                

            final MenuItems menuItems = new MenuItems();
            menuItems.menu = map;
            return menuItems;
        }
    }

    public static void main(final String[] args) throws IOException {

        ObjectMapper mapper = new ObjectMapper();
        SimpleModule module = new SimpleModule("SimpleModule",
                new Version(1,0,0,null));
        module.addDeserializer(MenuItems.class, new MenuItemsDeserializer());
        mapper.registerModule(module);

        MenuItems menuItems = mapper.readValue(INPUT, MenuItems.class);

    }
}

answered Mar 15, 2015 at 21:35

Stephen L.

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3 Comments

murman Over a year ago

Thanks Stephen! This idea really works :) Appreciated your help and thanks again!

murman Over a year ago

Hi Stephen! How this will work if two array comes from json request?

Stephen L. Over a year ago

Then you have to iterate over elements of your array and create a map.

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