Jackson JSON - Using @JsonIgnore and @JsonIgnoreProperties to ignore properties

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Following example shows how to use @JsonIgnore and @JsonIgnoreProperties annotations to ignore properties.

@JsonIgnore Example

@JsonIgnore can be used on fields or getters or setters to ignore individual properties.

public class Employee {
  private String name;
  private String dept;
  @JsonIgnore
  private String address;
    .............
}

public class ExampleMain {
  public static void main(String[] args) throws IOException {
      Employee employee = new Employee();
      employee.setName("Trish");
      employee.setDept("Admin");
      employee.setAddress("421 Moon Hill");

      //convert to json
      String jsonString = toJson(employee);
      System.out.println(jsonString);
      //convert to object;
      Employee e = toEmployee(jsonString);
      System.out.println(e);

      //address here will be ignore too
      String s = "{\"name\":\"Trish\",\"dept\":\"Admin\", \"address\":\"xyz Street\"}";
      System.out.println("JSON input: "+s);
      Employee e2 = toEmployee(s);
      System.out.println(e2);
  }

  private static Employee toEmployee(String jsonData) throws IOException {
      ObjectMapper om = new ObjectMapper();
      return om.readValue(jsonData, Employee.class);
  }

  private static String toJson(Employee employee) throws IOException {
      ObjectMapper om = new ObjectMapper();
      return om.writeValueAsString(employee);
  }
}

{"name":"Trish","dept":"Admin"}
Employee{name='Trish', dept='Admin', address='null'}
JSON input: {"name":"Trish","dept":"Admin", "address":"xyz Street"}
Employee{name='Trish', dept='Admin', address='null'}

@JsonIgnoreProperties Example

This annotation can be used to ignore multiple properties with one declaration:

@JsonIgnoreProperties({"dept", "address"})
public class Employee2 {
  private String name;
  private String dept;
  private String address;
    .............
}

public class ExampleMain2 {
  public static void main(String[] args) throws IOException {
      Employee2 employee = new Employee2();
      employee.setName("Trish");
      employee.setDept("Admin");
      employee.setAddress("421 Moon Hill");

      //convert to json
      String jsonString = toJson(employee);
      System.out.println(jsonString);
      //convert to object;
      Employee2 e = toEmployee(jsonString);
      System.out.println(e);

      //address/dept here will be ignored even they are in the source JSON
      String s = "{\"name\":\"Trish\",\"dept\":\"Admin\", \"address\":\"xyz Street\"}";
      System.out.println("JSON input: "+s);
      Employee2 e2 = toEmployee(s);
      System.out.println(e2);
  }

  private static Employee2 toEmployee(String jsonData) throws IOException {
      ObjectMapper om = new ObjectMapper();
      return om.readValue(jsonData, Employee2.class);
  }

  private static String toJson(Employee2 employee) throws IOException {
      ObjectMapper om = new ObjectMapper();
      return om.writeValueAsString(employee);
  }
}

{"name":"Trish"}
Employee{name='Trish', dept='null', address='null'}
JSON input: {"name":"Trish","dept":"Admin", "address":"xyz Street"}
Employee{name='Trish', dept='null', address='null'}

Ignoring Unknown Properties

@JsonIgnoreProperties#ignoreUnknown can be used to ignore a JSON property if is not defined in the POJO:

@JsonIgnoreProperties(ignoreUnknown = true)
public class Employee3 {
  private String name;
  private String dept;
  private String address;
    .............
}

public class ExampleMain3 {
  public static void main(String[] args) throws IOException {
      String jsonString = "{\"name\":\"Trish\",\"phone\":\"111-111-1111\"}";
      System.out.println(jsonString);
      //convert to object;
      Employee3 e = toEmployee(jsonString);
      System.out.println(e);
  }

  private static Employee3 toEmployee(String jsonData) throws IOException {
      ObjectMapper om = new ObjectMapper();
      return om.readValue(jsonData, Employee3.class);
  }
}

{"name":"Trish","phone":"111-111-1111"}
Employee{name='Trish', dept='null', address='null'}

Without `ignoreUnknown = true`, we will have following exception:

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "phone" (class com.logicbig.example.Employee3), not marked as ignorable (3 known properties: "name", "address", "dept"])
 at [Source: (String)"{"name":"Trish","phone":"111-111-1111"}"; line: 1, column: 26] (through reference chain: com.logicbig.example.Employee3["phone"])
	at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:60)
	at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:822)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:1152)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1567)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1545)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2992)
	at com.logicbig.example.ExampleMain3.toEmployee(ExampleMain3.java:18)
	at com.logicbig.example.ExampleMain3.main(ExampleMain3.java:12)