JsonIgnore on Field vs JsonIgnore on getter of a field in Jackson

Question

What is the difference between JsonIgnore on Field vs JsonIgnore on a getter of a field in Jackson?

Answer 1

@JsonIgnore annotation is used to ignore fields from de-serialization and serialization, it can be put directly on the instance member or on its getter or its setter. The application of the annotation in any of these 3 points, leads to the total exclusion of the property from both the serialization and de-serialization processes (and this applies starting from Jackson 1.9; the version used in these examples is Jackson 2.4.3).

Note: Before version 1.9, this annotation worked purely on method-by-method (or field-by-field) basis; annotation on one method or field did not imply ignoring other methods or fields

Example

 import java.io.IOException;

 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.core.JsonParseException;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.ObjectMapper;

 class MyTestClass {

 private long id;
 private String name;
 private String notInterstingMember;
 private int anotherMember;
 private int forgetThisField;

 public long getId() {
    return this.id;
 }

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

 public String getName() {
     return this.name;
 }

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

 @JsonIgnore
 public String getNotInterstingMember() {
    return this.notInterstingMember;
 }

 public void setNotInterstingMember(String notInterstingMember) {
    this.notInterstingMember = notInterstingMember;
 }

 public int getAnotherMember() {
    return this.anotherMember;
 }

 public void setAnotherMember(int anotherMember) {
    this.anotherMember = anotherMember;
 }

 public int getForgetThisField() {
    return this.forgetThisField;
 }

 @JsonIgnore
 public void setForgetThisField(int forgetThisField) {
    this.forgetThisField = forgetThisField;
 }

 @Override
 public String toString() {
    return "MyTestClass [" + this.id + " , " +  this.name + ", " + this.notInterstingMember + ", " + this.anotherMember + ", " + this.forgetThisField + "]";
    }

  }

Output:

 {"id":1,"name":"Test program","anotherMember":100}
 MyTestClass [1 , Test program, null, 100, 0]

But still it is possible to change this behavior and make it asymmetric, for example to exclude a property only from the deserialization using the @JsonIgnore annotation together with another annotation called @JsonProperty.