Test.java

package jackson;


import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

import java.io.IOException;


public class Test {

    private static class Foo {
        @JsonProperty("bar")
        @JsonSerialize(using = BarToString.class)
        Bar bar;
    }

    static class Bar {
        String s = "";

        Bar(String s) {
            this.s = s;
        }
    }

    private static class BarToString extends JsonSerializer<Bar> {
        @Override
        public void serialize(Bar bar, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws
            IOException {
            jsonGenerator.writeString(bar.s);
        }
    }


    public static void main(String[] args) throws Exception {
        ObjectMapper objectMapper = new ObjectMapper();

        Foo foo = new Foo();
        foo.bar = new Bar("yyy");

        String json = objectMapper.writeValueAsString(foo);
        System.out.println(json); //{"bar":"yyy"}

        Foo fooDeserialized = objectMapper.readValue(json, Foo.class);
        System.out.println(fooDeserialized.bar.s); //yyy
    }
}