AutoJackson

Annotations to avoid manually adding Jackson annotaions to your model classes to facilitate JSON serialization and deserialization.

Annotations

@AutoJackson

Annotation placed on interfaces to automatically generate the needed deserializers and classes needed to create concrete instances of those interfaces. An AutoJackson.Type can be given to the annotation when more than one class needs to implement a given interface.

@AutoJacksonTypeClass

When needing to have multiple concrete implementation of an interface, the class passed into the AutoJackson.Type needs to have an accessor annotated with this annotation. This is required to know which method will return the Class definition for the interface that matches the enumeration value for the class passed in to the AutoJackson.Type.

See the usage below for an example

@Named

Annotation placed on methods of the interface to expliclty controll the JSON key used for that item. If not provided a method in the form of getSuperItem() is expected, and would default to superItem.

Usage after applying annotations

AutoJacksonSetup.Java

After all the classes have been annotated and compiled an additional class is created to avoid the boiler plate of adding each of the Jackson deserializers to the ObjectMapper used for deserializtion.

ObjectMapper objectMapper = ...
AutoJacksonSetup.configureObjectMapper( objectMapper );

Using the configuration avoids having to add each custom deserializer manually, such as:

ObjectMapper objectMapper = ...
SimpleModule deserialzationModule = new SimpleModule();
deserialzationModule.addDeserializer(Fraggle.class, new Fraggle_AutoJacksonDeserializer());
deserialzationModule.addDeserializer(Muppet.class, new Muppet_AutoJacksonDeserializer());
deserialzationModule.addDeserializer(SillyCreature.class, new SillyCreature_AutoJacksonDeserializer());
objectMapper.registerModule(deserialzationModule);

Example

Given the example JSON document:

{
  "fraggles" : [
    {
      "name" : "BOOBER",
      "hairColour" : "blue",
      "hat" : true,
      "job" : {
        "occupation" : "Actor",
        "daysWorked" : 0
      }
    },
    {
      "name" : "WEMBLEY",
      "hairColour" : "yellow",
      "hat" : false
    }
  ]
}

Rather than using the full Jackson annotations for the JSON processing AutoJackson can be used to simplify your models.

 

 

FraggleList.java - Standard Jackson Annotations

public class FraggleList {
    private static final String FRAGGLES_KEY = "fraggles";

    @JsonProperty(value = FRAGGLES_KEY, required = true)
    private final List<Fraggle> fraggles;

    public FraggleList(@JsonProperty(value = FRAGGLES_KEY, required = true) List<Fraggle> fraggles) {
        this.fraggles = fraggles;
    }

    public List<Fraggle> getFraggles() {
        return this.fraggles;
    }
}

FraggleList.java - AutoJackson Annotations

@AutoJackson
public interface FraggleList {
    List<Fraggle> getFraggles();
}

 

 

Fraggle.java - Standard Jackson Annotations

@JsonTypeInfo(use = Id.NAME,
        include = JsonTypeInfo.As.PROPERTY,
        property = "name") // not compile time checked
@JsonSubTypes({
        @Type(value = Wembley.class, name = "WEMBLEY"), // not compile time checked
        @Type(value = Boober.class, name = "BOOBER")    // not compile time checked
})
public abstract class Fraggle {
    protected static final String HAIR_COLOUR_KEY = "hairColour";
    protected static final String HAT_KEY = "hat";
    protected static final String JOB_KEY = "job";

    @JsonProperty(value = HAIR_COLOUR_KEY, required = true)
    private final String hairColour;

    @JsonProperty(value = HAT_KEY, required = true)
    private final Boolean wearsHats;

    @JsonProperty(value = JOB_KEY)
    private final Optional<Job> job;

    protected Fraggle(String hairColour, Boolean wearsHats, Optional<Job> job) {
        this.hairColour = hairColour;
        this.wearsHats = wearsHats;
        this.job = job;
    }

    @JsonIgnore
    public abstract FraggleName getFraggleName();

    public String getHairColour() {
        return this.hairColour;
    }

    public Boolean wearsHats() {
        return this.wearsHats;
    }

    public Optional<Job> getJob() {
        return this.job;
    }

    public enum FraggleName {
        WEMBLEY, BOOBER
    }
}

Fraggle.java - AutoJackson Annotations

@AutoJackson
public interface Fraggle {
    FraggleName getName();
    String getHairColour();
    @Named("hat") Boolean wearsHats();
    Optional<Job> getJob();
    
    enum FraggleName {
        WEMBLEY(Wembley.class),
        BOOBER(Boober.class),

        private final Class<? extends Fraggle> fraggleClass;

        FraggleName(Class<? extends Fraggle> fraggleClass) {
            this.fraggleClass = fraggleClass;
        }

        @AutoJacksonTypeClass
        public Class<? extends Fraggle> getFraggleClass() {
            return fraggleClass;
        }
    }
}

 

 

Job.java - Standard Jackson Annotations

public class Job {
    private static final String OCCUPATION_KEY = "occupation";
    private static final String DAYS_WORKED_KEY = "daysWorked";

    @JsonProperty(value = OCCUPATION_KEY, required = true)
    private final String occupation;

    @JsonProperty(value = DAYS_WORKED_KEY, required = true)
    private final int daysWorked;

    public Job(@JsonProperty(value = OCCUPATION_KEY, required = true) String occupation,
               @JsonProperty(value = DAYS_WORKED_KEY, required = true) int daysWorked) {
        this.occupation = occupation;
        this.daysWorked = daysWorked;
    }

    public String getOccupation() {
        return this.occupation;
    }

    public int getDaysWorked() {
        return this.daysWorked;
    }
}

Job.java - AutoJackson Annotations

@AutoJackson
public interface Job {
    String getOccupation();
    int getDaysWorked();
}

 

 

Wembley.java - Standard Jackson Annotations

public class Wembley extends Fraggle {
    public Wembley(@JsonProperty(value = HAIR_COLOUR_KEY, required = true) String hairColour,
                   @JsonProperty(value = HAT_KEY, required = true) Boolean wearsHats,
                   @JsonProperty(value = JOB_KEY) Optional<Job> job) {
        super(hairColour, wearsHats, job);
    }

    @Override
    public FraggleName getFraggleName() {
        return FraggleName.WEMBLEY;
    }
}

Wembley.java - AutoJackson Annotations

@AutoJackson
public interface Wembley { }

 

 

Boober.java - Standard Jackson Annotations

public class Boober extends Fraggle {
    public Boober(@JsonProperty(value = HAIR_COLOUR_KEY, required = true) String hairColour,
                  @JsonProperty(value = HAT_KEY, required = true) Boolean wearsHats,
                  @JsonProperty(value = JOB_KEY) Optional<Job> job) {
        super(hairColour, wearsHats, job);
    }

    @Override
    public FraggleName getFraggleName() {
        return FraggleName.BOOBER;
    }
}

Boober.java - AutoJackson Annotations

@AutoJackson
public interface Boober { }

 

Additional Examples

See the packaged example models for a more complex example.

---

Getting Autojackson

The autojackson-processor package contains the annotations and processor code that must be included.

With Maven:

<dependency>
    <groupId>com.github.peckb1</groupId>
    <artifactId>autojackson-processor</artifactId>
    <version>1.1.1</version>
</dependency>

With Gradle:

compile 'com.github.peckb1:autojackson-processor:1.1.1'

Snapshots of the development version are available in Sonatype's snapshots repository.