Jackson JSON - Using @JsonProperty, @JsonSetter and @JsonGetter to rename property names

Using @JsonProperty

Following example shows how to use @JsonProperty annotation to rename properties. This annotation can be used on fields or getters or setters.

public class ExampleMain {
    public static void main(String[] args) throws IOException {
        Employee employee = new Employee();
        employee.setName("Trish");
        employee.setDept("Admin");

        //convert to json
        String jsonString = toJson(employee);
        System.out.println(jsonString);
        //convert to object
        Employee e = toEmployee(jsonString);
        System.out.println(e);
    }

    private static Employee toEmployee(String jsonData) throws IOException {
        ObjectMapper om = new ObjectMapper();
        return om.readValue(jsonData, Employee.class);
    }

    private static String toJson(Employee employee) throws IOException {
        ObjectMapper om = new ObjectMapper();
        return om.writeValueAsString(employee);
    }

    private static class Employee {
        @JsonProperty("employee-name")
        private String name;
        @JsonProperty("employee-dept")
        private String dept;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getDept() {
            return dept;
        }

        public void setDept(String dept) {
            this.dept = dept;
        }

        @Override
        public String toString() {
            return "Employee{" +
                    "name='" + name + '\'' +
                    ", dept='" + dept + '\'' +
                    '}';
        }
    }
}

{"employee-name":"Trish","employee-dept":"Admin"}
Employee{name='Trish', dept='Admin'}

Using @JsonGetter and @JsonSetter

@JsonGetter and @JsonSetter are old alternatives to @JsonProperty.

public class ExampleMain2 {
    public static void main(String[] args) throws IOException {
        Employee employee = new Employee();
        employee.setName("Trish");
        employee.setDept("Admin");

        //convert to json
        String jsonString = toJson(employee);
        System.out.println(jsonString);
        //convert to object
        Employee e = toEmployee(jsonString);
        System.out.println(e);
    }

    private static Employee toEmployee(String jsonData) throws IOException {
        ObjectMapper om = new ObjectMapper();
        return om.readValue(jsonData, Employee.class);
    }

    private static String toJson(Employee employee) throws IOException {
        ObjectMapper om = new ObjectMapper();
        return om.writeValueAsString(employee);
    }

    private static class Employee {
        private String name;
        private String dept;

        @JsonGetter("employee-name")
        public String getName() {
            return name;
        }

        @JsonSetter("employee-name")
        public void setName(String name) {
            this.name = name;
        }

        @JsonGetter("employee-dept")
        public String getDept() {
            return dept;
        }

        @JsonSetter("employee-dept")
        public void setDept(String dept) {
            this.dept = dept;
        }

        @Override
        public String toString() {
            return "Employee{" +
                    "name='" + name + '\'' +
                    ", dept='" + dept + '\'' +
                    '}';
        }
    }
}

{"employee-name":"Trish","employee-dept":"Admin"}
Employee{name='Trish', dept='Admin'}

Handling Nulls with @JsonSetter

Besides renaming , the annotation @JsonSetter can be used to specify how 'null' values in JSON should be mapped to Java properties. For example:

public class ExampleMain3 {
    public static void main(String[] args) throws IOException {
        String jsonString = "{\"name\":null}";
        System.out.println(jsonString);
        //convert to Person
        Person person = toPerson(jsonString);
        System.out.println(person);
    }

    private static Person toPerson(String jsonData) throws IOException {
        ObjectMapper om = new ObjectMapper();
        return om.readValue(jsonData, Person.class);
    }

    private static class Person {
        private String name;

        @JsonSetter(nulls = Nulls.AS_EMPTY)
        public void setName(String name) {
            this.name = name;
        }

        public String getName() {
            return name;
        }

        @Override
        public String toString() {
            return "Person{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }
}

{"name":null}
Person{name=''}

Without @JsonSetter (or with @JsonSetter but without any Nulls parameter) the output would be:

{"name":null}
Person{name='null'}

Other elements of Nulls enum are: SET, SKIP, FAIL, AS_EMPTY and DEFAULT.

Example Project

Dependencies and Technologies Used:

• jackson-databind 2.9.3: General data-binding functionality for Jackson: works on core streaming API.
• JDK 9
• Maven 3.3.9