Why can't I unwrap the root node and deserialize an array of objects?

Question

Why am I not able to deserialize an array of objects by unwrapping the root node?

import java.io.IOException;
import java.util.Arrays;
import java.util.List         


        

Answer 1

Create an ObjectReader to configure the root name explicitly:

@Test
public void testUnwrapping() throws IOException {
    String json = "{\"customers\":[{\"email\":\"hello@world.com\"},{\"email\":\"john.doe@example.com\"}]}";
    ObjectReader objectReader = mapper.reader(new TypeReference>() {})
                                      .withRootName("customers");
    List customers = objectReader.readValue(json);
    assertThat(customers, contains(customer("hello@world.com"), customer("john.doe@example.com")));
}

(btw this is with Jackson 2.5, do you have a different version? I have DeserializationFeature rather than DeserializationConfig.Feature)

It seems that by using an object reader in this fashion, you don't need to globally configure the "unwrap root value" feature, nor use the @JsonRootName annotation.

Note also that you can directly request a List rather than going through an array- the type given to ObjectMapper.reader works just like the second parameter to ObjectMapper.readValue