Question 212747 in Json Question posted in
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How can I convert json with uppercased field names to object?

I have json

{
    "Person": {
        "PersonId": 122,
        "Name": "John",
        "Surname": "Doe",
        "age": 2
    }
}

I want to convert it to Java class

    public class Person {
        private String personId;
        private String name;
        private String surname;
        private int age;
        
        //getters,setters...
    }

And I don’t have permission to change this Person class.

What I already have tried is


    @Bean
    ObjectMapper objectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(new LowerCaseStrategy());
        return mapper;
    }

    public static class LowerCaseStrategy extends PropertyNamingStrategy.PropertyNamingStrategyBase {
        @Override
        public String translate(String input) {
            char[] chars = input.toCharArray();
            chars[0] = Character.toLowerCase(chars[0]);
            return new String(chars);
        }
    }

But it did not help.

Does anyone have an idea how this can be solved?

Tags:

2

Answers


  1. 0

    To convert the JSON with uppercased field names to the desired Java class, you can use the @JsonProperty annotation from Jackson library. Here’s how you can modify your Person class and ObjectMapper configuration to achieve the conversion:

    1. Modify the Person class to use the @JsonProperty annotation:
    public class Person {
    @JsonProperty("PersonId")
    private String personId;
    
    @JsonProperty("Name")
    private String name;
    
    @JsonProperty("Surname")
    private String surname;
    
    @JsonProperty("age")
    private int age;

    // Getters and setters...
}
    1. Remove the custom LowerCaseStrategy from your ObjectMapper configuration since the field names in your JSON are already in lowercase.
    @Bean
public ObjectMapper objectMapper() {
    return new ObjectMapper();
}

    Now, when you deserialize the JSON using the updated ObjectMapper, it will correctly map the fields with uppercased names to the corresponding fields in the Person class.

    For example:

    String jsonString = "{"Person":{"PersonId":122,"Name":"John","Surname":"Doe","age":2}}";

ObjectMapper objectMapper = new ObjectMapper();
Person person = objectMapper.readValue(jsonString, Person.class);

System.out.println(person.getPersonId()); // Output: 122
System.out.println(person.getName()); // Output: John
System.out.println(person.getSurname()); // Output: Doe
System.out.println(person.getAge()); // Output: 2

    With these changes, the JSON with uppercased field names will be correctly converted to the Java Person object.

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  2. 0

    You are almost there. The one error you made, is the direction in which the PropertyNamingStrategy applies: You are converting from Java name, to JSON name, not the other way around. So, this should work:

            @Override
        public String translate(String input) {
            char[] chars = input.toCharArray();
            chars[0] = Character.toUpperCase(chars[0]); // upper!
            return new String(chars);
        }

    Also, Jackson has PropertyNamingStrategies.UPPER_CAMEL_CASE which should do the thing you need without implementing your own.

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