exapple with custom serializer for http://stackoverflow.com/questions/29540396/jackson-custom-serialization-getter

CustomSerializerTest.java

package makasprzak.stackoverflow;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
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 com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.util.Converter;
import org.fest.assertions.Assertions;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.runners.MockitoJUnitRunner;

import java.io.IOException;

import static makasprzak.stackoverflow.CustomSerializerTest.User.Builder.user;
import static org.fest.assertions.Assertions.assertThat;

@RunWith(MockitoJUnitRunner.class)
public class CustomSerializerTest {

   private final ObjectMapper objectMapper = new ObjectMapper();

   @Test
   public void shouldSerializeWithUpperCasedUsername() throws Exception {
      assertThat(objectMapper.writeValueAsString(user()
         .withId(1L)
         .withUsername("macias")
         .build())).contains("MACIAS").doesNotContain("macias");
   }

   @Test
   public void shouldSerializeWithLowerCasedUsername() throws Exception {
      assertThat(objectMapper.writeValueAsString(user()
         .withId(0L)
         .withUsername("macias")
         .build())).contains("macias").doesNotContain("MACIAS");
   }

   public static class UserSerializer extends JsonSerializer<User> {
      public static class UserWrapper {
         public Long id;
         public String username;
      }

      @Override
      public void serialize(User user, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
         UserWrapper userWrapper = new UserWrapper();
         userWrapper.id = user.getId();
         userWrapper.username = user.getId() % 2 == 0 ? user.getUsername() : user.getUsername().toUpperCase();
         serializerProvider.defaultSerializeValue(userWrapper,jsonGenerator);
      }


   }

   @JsonSerialize(using = UserSerializer.class)
   public static class User {
      private Long id;
      private String username;

      public Long getId() {
         return id;
      }

      public void setId(Long id) {
         this.id = id;
      }

      public String getUsername() {
         return username;
      }

      public void setUsername(String username) {
         this.username = username;
      }

      public static interface IdStep {
         UsernameStep withId(Long id);
      }

      public static interface UsernameStep {
         BuildStep withUsername(String username);
      }

      public static interface BuildStep {
         User build();
      }


      public static class Builder implements IdStep, UsernameStep, BuildStep {
         private Long id;
         private String username;

         private Builder() {
         }

         public static IdStep user() {
            return new Builder();
         }

         @Override
         public UsernameStep withId(Long id) {
            this.id = id;
            return this;
         }

         @Override
         public BuildStep withUsername(String username) {
            this.username = username;
            return this;
         }

         @Override
         public User build() {
            User user = new User();
            user.setId(this.id);
            user.setUsername(this.username);
            return user;
         }
      }
   }
}