Spring boot jackson - deserializes Json with root name - json

Question

I have the below Json
{
"user": {
"name": "Ram",
"age": 27
}
}
which I want to de-serialize into an instance of the class
public class User {
private String name;
private int age;
// getters & setters
}
For this, I have used #JsonRootName on class name and something like below
#Configuration
public class JacksonConfig {
#Bean
public Jackson2ObjectMapperBuilder jacksonBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.featuresToEnable(DeserializationFeature.UNWRAP_ROOT_VALUE);
return builder;
}
}
But it did not work as expected. If I send something like below, it worked.
{
"name": "Ram",
"age": 27
}
But I want to get the json de-serialized with root name. Can any one please suggest?
I want to spring boot way of doing this.

Answer 1

#JsonRootName is a good start. Use this annotation on User class and then enable UNWRAP_ROOT_VALUE deserialization feature by adding:
spring.jackson.deserialization.UNWRAP_ROOT_VALUE=true
to your application.properties.
Read more about customizing Jackson mapper in Spring Boot Reference

Answer 2

Using ObjectMapper you can resolve this issue easily. Here's what you have to do :
- Annotate User class as given below
#JsonRootName("user")
public class User {
private String name;
private int age;
// getters & setters
}
Create CustomJsonMapper class
public class CustomJsonMapper extends ObjectMapper {
private DeserializationFeature deserializationFeature;
public void setDeserializationFeature (DeserializationFeature deserializationFeature) {
this.deserializationFeature = deserializationFeature;
enable(this.deserializationFeature);
}
}
Equivalent Spring configuration
<bean id="objectMapper" class=" com.cognizant.tranzform.notification.constant.CustomJsonMapper">
<property name="deserializationFeature" ref="deserializationFeature"/>
</bean>
<bean id="deserializationFeature" class="com.fasterxml.jackson.databind.DeserializationFeature"
factory-method="valueOf">
<constructor-arg>
<value>UNWRAP_ROOT_VALUE</value>
</constructor-arg>
</bean>
Using following code you can test
ApplicationContext context = new ClassPathXmlApplicationContext(
"applicationContext.xml");
ObjectMapper objectMapper = (ObjectMapper) context
.getBean("objectMapper");
String json = "{\"user\":{ \"name\": \"Ram\",\"age\": 27}}";
User user = objectMapper.readValue(json, User.class);