Customize Serialization Output with @JsonValue

Jackson

The @JsonValue annotation is used to indicate that a method in a class should be used for serialization. When you apply this annotation to a method, Jackson will invoke that method to determine how the object should be represented in the JSON output.

Using @JsonValue

To utilize the @JsonValue annotation with a Person class, follow these steps:

  • Create a method in your Person class that should be used for serialization. This method should return your desired format representing of the object.
  • Annotate the method with @JsonValue.

    class Person {

        private Long id;
        private String name;
        private String dateOfBirth;

        @JsonValue
        public String toJson() {
            return "ID: " + id + ", Name: " + name;
        }
    }

In this example, the Person class has a method named toJson, which is annotated with @JsonValue. When serializing a Person object, Jackson will invoke this method to determine the custom representation.

    Person person = new Person(1L, "Alice", "1990-01-15");
    ObjectMapper objectMapper = new ObjectMapper();
    String customFormat = objectMapper.writeValueAsString(person);
    System.out.println("Serialized Person: " + customFormat);

Output:

Serialized Person: "ID: 1, Name: Alice"

When to Use @JsonValue

The @JsonValue annotation is particularly useful in the following scenarios:

  • Custom Serialization Logic: When you need to apply custom serialization logic to an object. This is handy when the default serialization of the object doesn’t meet your requirements.
  • Simplifying JSON Output: When you want to simplify the JSON output by directly mapping an object to a simple value without wrapping it in an additional JSON object.

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