Jackson

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-core</artifactId>
  <version>2.9.6</version>
</dependency>

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-annotations</artifactId>
  <version>2.9.6</version>
</dependency>

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.9.6</version>
</dependency>

CBOR encoded data with Jackson

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-cbor</artifactId>
    <version>2.9.6</version>
</dependency>    

In order to read and write MessagePack encoded data

<dependency>
    <groupId>org.msgpack</groupId>
    <artifactId>jackson-dataformat-msgpack</artifactId>
    <version>0.8.16</version>
</dependency>

com.fasterxml.jackson.databind.ObjectMapper [databind has objectMapper]

ObjectMapper is because it maps JSON into Java Objects (deserialization), or Java Objects into JSON (serialization).

Add caption

Custom Deserializer 

 1. Create SimpleModule

 2.   Register   objectmapper.registerModule(module);

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;

public Car deserialize(JsonParser parser, DeserializationContext deserializer) 
throws IOException {

https://spin.atomicobject.com/2016/07/01/custom-serializer-jackson/

https://fasterxml.github.io/jackson-databind/javadoc/2.9/com/fasterxml/jackson/databind/module/SimpleModule.html

Custom Serializer

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;

  public void serialize(Car car, JsonGenerator jsonGenerator,
                          SerializerProvider serializerProvider)

JsonNode

com.fasterxml.jackson.databind.JsonNode is Jackson's tree model

ObjectMapper objectMapper = new ObjectMapper();

JsonNode jsonNode = objectMapper.readTree(json)

ObjectMapper objectMapper = new ObjectMapper();

JsonNode jsonNode = readJsonIntoJsonNode();

String json = objectMapper.writeValueAsString(jsonNode);

• Read + Write Annotations
• @JsonIgnore
•  is used to tell Jackson to ignore a certain property (field) of a Java object.

•  @JsonIgnore
      public long    personId = 0;

• @JsonIgnoreProperties

@JsonIgnoreProperties({"firstName", "lastName"})
public class PersonIgnoreProperties {

• @JsonIgnoreType   marks whole class as ignored

 @JsonIgnoreType
    public static class Address {
        public String streetName  = null;
        public String houseNumber = null;
        public String zipCode     = null;
        public String city        = null;
        public String country     = null;
    }

• @JsonAutoDetect  inculdes private properties

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY )
public class PersonAutoDetect {

    private long  personId = 123;
    public String name     = null;
 

}Read Annotations
• @JsonSetter  use it when property name is not same as field name in class

•    public long getPersonId() { return this.personId; }
      @JsonSetter("id")
      public void setPersonId(long personId) { this.personId = personId; }

• @JsonAnySetter
is used for calling unrecognized properties
• @JsonCreator
we must add the @JsonCreator annotation to the constructor. But that alone is not enough. We must also annotate the parameters of the constructor to tell Jackson which fields from the JSON object to pass to which constructor parameters.

@JsonCreator
    public PersonImmutable(
            @JsonProperty("id")  long id,
            @JsonProperty("name") String name  ) {

        this.id = id;
        this.name = name;
    }



• @JacksonInject
The Jackson annotation @JacksonInject is used to inject values into the parsed objects, instead of reading those values from the JSON
• @JsonDeserialize
The Jackson annotation @JsonDeserialize is used to specify a custom de-serializer class for a given field in a Java object.


• Write Annotations
1. @JsonInclude
• The Jackson annotation @JsonInclude tells Jackson only to include properties under certain circumstances. For instance, that properties should only be included if they are non-null, non-empty, or have non-default values. 
• 
  

• @JsonInclude(JsonInclude.Include.NON_EMPTY)
  public class PersonInclude {
  
      public long  personId = 0;
      public String name     = null;
  
  }

• @JsonGetter
same as setter except its getter
• @JsonAnyGetter
• @JsonPropertyOrder

• @JsonPropertyOrder({"name", "personId"})
  public class PersonPropertyOrder {
  
  

• @JsonRawValue


• @JsonValue
• @JsonSerialize tells to use custom serializer for a property

public class PersonSerializer {

    public long   personId = 0;
    public String name     = "John";

    @JsonSerialize(using = OptimizedBooleanSerializer.class)
    public boolean enabled = false;
}

Jackson Annotations

@JsonIdentityInfo allows to serialize a POJO by id but only when it is encountered second time during serialization.
 @JsonIdentityReference serialize the POJO by id the first time it is encountered.

package example;

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.JsonIdentityReference;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;

@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,
                  property = "id")
@JsonIdentityReference(alwaysAsId = true)
public class Student {}
}

https://www.logicbig.com/tutorials/misc/jackson/json-identity-reference.html

____________________________________________________________________________

@JsonIgnore instead is a member-level or method-level annotation, which expects that the properties to be excluded are marked one by one.


@JsonIgnore@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "reroute")
public Set getEmployee() {
   return this.employee;
}

@JsonIgnoreProperties is an annotation at the class level and it expects that the properties to be excluded would be explicitly indicated in the form of a list of strings.

@JsonPropertyOrder : Defines ordering to use while serializing

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonPropertyOrder({ "id", "doj", "employee"})
public class EmploymentDetails {

@JsonIgnoreProperties(value = {"employee"}, ignoreUnknown = true)
      @JsonPropertyOrder({ "id", "doj", "employee"})
public class EmploymentDetails {

______________________________________________________________________________

https://www.logicbig.com/tutorials/misc/jackson.html


@JsonIgnoreType can be used to ignore the whole class,

https://www.logicbig.com/tutorials/misc/jackson/json-ignore-type.html

@JacksonInject annotation is used to indicate that value of annotated property will be injected during deserialization.
This is useful if we want to add additional information which is not included in 

https://www.logicbig.com/tutorials/misc/jackson/jackson-inject.html

the source JSON.

@JsonAlias({"department", "employeeDept" })
private String dept;
_______________________________________________________________________________
 
@JsonCreator 

The @JsonCreator annotation can be used on constructors or factory methods for mapping incoming JSON properties to the constructor/factory method arguments. This annotation is used only during deserialization and can be particularly useful for immutable objects

https://spin.atomicobject.com/2016/07/01/custom-serializer-jackson/

https://www.logicbig.com/tutorials/misc/jackson/json-serialize-deserialize-converter.html