ObjectMapper readValue

Question

I load a ressource file json with the text format

{
    \"sources\": [{
            \"prop1\": \"1\",
            \"prop2\": \"2\"

        },
        {
                 


        

Answer 1

First thing: Your JSON is invalid. There is a comma after the second object in the sources array. This has to be deleted.

Second: I think you didn't choose the right type for your result. What your JSON represents is a map which maps from string to an array of objects. So the type should be something like Map<String, Props[]> (Since you didn't provide the name of your class, I called it Props.

With these considerations you can construct a MapType by using ObjectMappers getTypeFactory() method and deserialize the value using the constructed type like shown below.

ObjectMapper mapper = new ObjectMapper();
TypeFactory typeFactory = mapper.getTypeFactory();
MapType mapType = typeFactory.constructMapType(HashMap.class, String.class, Props[].class);
Map<String, Props[]> map = mapper.readValue(s, mapType);

Answer 2

I actually voted for the other answer, but this is my idea, to create the classes and let jackson do the work :

public class ResourceTest {

    @Test
    public void test1() throws IOException {
        assertTrue(true);

        Resource resource = new Resource();

        resource.getRedirectrions().add(makeRedirectrion("rprop11", "rprop12"));
        resource.getRedirectrions().add(makeRedirectrion("rprop21", "rprop22"));

        resource.getSources().add(makeSource("sprop11","sprop12"));
        resource.getSources().add(makeSource("sprop21","sprop22"));

        String json = new ObjectMapper().writeValueAsString(resource);
        System.out.println(json);

        Resource resource1 = new ObjectMapper().readValue(json, Resource.class);
        System.out.println(resource1);
    }

    private Source makeSource(String prop1, String prop2) {
        Source source = new Source();
        source.setProp1(prop1);
        source.setProp2(prop2);
        return source;
    }

    private Redirectrion makeRedirectrion(String prop1, String prop2) {
        Redirectrion redirectrion = new Redirectrion();
        redirectrion.setProp1(prop1);
        redirectrion.setProp2(prop2);
        return redirectrion;
    }

}

Output is:

{"sources":[{"prop1":"sprop11","prop2":"sprop12"},{"prop1":"sprop21","prop2":"sprop22"}],"redirectrions":[{"prop1":"rprop11","prop2":"rprop12"},{"prop1":"rprop21","prop2":"rprop22"}]}
Resource{sources=[Source{prop1='sprop11', prop2='sprop12'}, Source{prop1='sprop21', prop2='sprop22'}], redirectrions=[Source{prop1='rprop11', prop2='rprop12'}, Source{prop1='rprop21', prop2='rprop22'}]}

Answer 3

In your case, I would write a custom JsonDeserializer. Haven't really tested the code, but I think the idea is clear:

    final MyClassDeserializer myClassDeserializer = new MyClassDeserializer();
    final SimpleModule deserializerModule = new SimpleModule();
    deserializerModule.addDeserializer(MyClass.class, myClassDeserializer);

    final ObjectMapper mapper = new ObjectMapper();
    mapper.registerModule(deserializerModule);

And the code for JsonDeserializer:

    public class MyClassDeserializer extends JsonDeserializer<MyClass> {

    @Override
    public MyClass deserialize(final JsonParser jsonParser, final DeserializationContext context)
            throws IOException {
        final JsonNode node = jsonParser.getCodec().readTree(jsonParser);
        final JsonNode sourcesNode = node.get("sources");
        if(node.isArray()) {
            final ArrayNode arrayNode = (ArrayNode) node;
            final Iterable<JsonNode> nodes = arrayNode::elements;
            final Set<Source> set = StreamSupport.stream(nodes.spliterator(), false)
                    .map(mapper)
                    .collect(Collectors.toSet());
            ...
        }

        ...
    }