Jackson JSON Deserialization with Root Element

Question

I am having a question with Jackson that I think should be simple to solve, but it is killing me.

Let's say I have a java POJO class that looks like this (assume Getters and Setters for me):

class User {     private String name;     private Integer age; } 

And I want to deserialize JSON that looks like this into a User object:

{   "user":     {       "name":"Sam Smith",       "age":1   } } 

Jackson is giving me issues because the User is not the first-level object in the JSON. I could obviously make a UserWrapper class that has a single User object and then deserialize using that but I know there must be a more elegant solution.

How should I do this?

Answer 1

edit: this solution only works for jackson < 2.0

For your case there is a simple solution:

• You need to annotate your model class with @JsonRootName(value = "user");
• You need to configure your mapper with om.configure(Feature.UNWRAP_ROOT_VALUE, true); (as for 1.9) and om.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true); (for version 2).

That's it!

---

@JsonRootName(value = "user") public static class User {     private String name;     private Integer age;      public String getName() {         return name;     }      public void setName(final String name) {         this.name = name;     }      public Integer getAge() {         return age;     }      public void setAge(final Integer age) {         this.age = age;     }      @Override     public String toString() {         return "User [name=" + name + ", age=" + age + "]";     }  }  ObjectMapper om = new ObjectMapper(); om.configure(Feature.UNWRAP_ROOT_VALUE, true); System.out.println(om.readValue("{  \"user\":    {      \"name\":\"Sam Smith\",      \"age\":1  }}", User.class)); 

this will print:

User [name=Sam Smith, age=1]