How to convert json into POJO in java using jackson

jackson, java, json, pojo, spring

Solution

What I did was this: I created a new class that holds a Person object and Dog object, these classes needs to be static ( I found it here ). Here are the classes:

public static class MyNewClass{
    private Person person;
    private Dog dog;
    ... // two constructors and getters and setters

 public static class Person{
     private String id;
     ... // two constructors and getters and setters
 }
 public static class Dog{
     private String dateOfBirth;
     private String price;
     ... // two constructors and getters and setters
  }
}

Now my code looks like this:

    JsonNode tree = mapper.readTree(jsonString);
    Iterator<JsonNode> iter = tree.path("data").getElements();
    while (iter.hasNext()){
        JsonNode node = iter.next();
        Person person = mapper.readValue(node.path("Person"), Person.class);
        Dog dog = mapper.readValue(node.path("Dog"), Dog.class);
        MyNewClass myNewClass = new MyNewClass(person , dog);
        ... //Do something with it
    }

I still want to do it without creating these two objects ( Person and Dog ) - That'a good enough for now - but if someone have an idea - I would like to here!

Thanks.

Problem

I'm using spring 3.1.2 and I need to parse a json object into POJO. This is the json that I need to parse: ``` { "Person" : { "id" : "2" }, "Dog" : { "dateOfBirth" : "2012-08-20 00:00:00", "price" : "10.00" } } ``` I need to convert this json object (which is combined from two objects) into one POJO, here it is: ``` public class MyClass{ public MyClass(){} public MyClass(String personsId, TimeStamp dogsDateOfBirth, BigDecimal dogsPrice){ .... // assign each parameter to the appropriate field } private String personsId; private TimeStamp dogsDateOfBirth; private BigDecimal dogsPrice; //... Getters and Setters for each field } ``` For that matter I used `ObjectMapper mapper = new ObjectMapper();` Now since I have several json objects my code looks like this: ``` String json = ... ;// A json with several objects as above JsonNode tree = mapper.readTree(json); Iterator<JsonNode> iter = tree.path("data").getElements(); while (iter.hasNext()){ JsonNode node = iter.next(); MyClass myClass = mapper.readValue(node, MyClass.class); ... // do something with myClass object } ``` When I run this - I get the following exception: ``` org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class ...MyClass]: can not instantiate from JSON object (need to add/enable type information?) ``` I tried to create a simple POJO - `Person`: ``` public class Person{ private String id; public Person(){} public Person(String id){ this.id = id; } ... // Getter and Setter } ``` and do the following: ``` Person person = mapper.readValue(node.path("Person"), Person.class); ``` I get this (same) exception: ``` org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class ...Person]: can not instantiate from JSON object (need to add/enable type information?) ``` I tried to read some about the type information - but couldn't understand how it can help me here. How can I convert this json into my POJO? Thanks.

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