Ignoring new fields on JSON objects using Jackson

Question

This question already has an answer here:

• Jackson with JSON: Unrecognized field, not marked as ignorable 32 answers

I'm using Jackson JSON library to convert some JSON objects to POJO classes on an android application. The problem is, the JSON objects might change and have new fields added while the application is published, but currently it will break even when a simple String field is added, which can safely be ignored.

Is there any way to tell Jackson to ignore newly added fields? (e.g. non-existing on the POJO objects)? A global ignore would be great.

Answer 1

Up to date and complete answer with Jackson 2

---

Using Annotation

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class MyMappingClass {

}

See JsonIgnoreProperties on Jackson online documentation.

Using Configuration

Less intrusive than annotation.

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

ObjectReader objectReader = objectMapper.reader(MyMappingClass.class);
MyMappingClass myMappingClass = objectReader.readValue(json);

See FAIL_ON_UNKNOWN_PROPERTIES on Jackson online documentation.

Answer 2

For whom are using Spring Boot, you can configure the default behaviour of Jackson by using the Jackson2ObjectMapperBuilder.

For example :

@Bean
public Jackson2ObjectMapperBuilder configureObjectMapper() {
    Jackson2ObjectMapperBuilder oMapper = new Jackson2ObjectMapperBuilder();
    oMapper.failOnUnknownProperties(false);
    return oMapper;
}

Then you can autowire the ObjectMapper everywhere you need it (by default, this object mapper will also be used for http content conversion).

Answer 3

I'm using jackson-xxx 2.8.5.Maven Dependency like:

<dependencies>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.8.5</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.8.5</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.8.5</version>
    </dependency>

</dependencies>

First,If you want ignore unknown properties globally.you can config ObjectMapper.
Like below:

ObjectMapper objectMapper = new ObjectMapper();

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

If you want ignore some class,you can add annotation @JsonIgnoreProperties(ignoreUnknown = true) on your class like:

@JsonIgnoreProperties(ignoreUnknown = true)
public class E1 {

    private String t1;

    public String getT1() {
        return t1;
    }

    public void setT1(String t1) {
        this.t1 = t1;
    }
}

Answer 4

Jackson provides an annotation that can be used on class level (JsonIgnoreProperties).

Add the following to the top of your class (not to individual methods):

@JsonIgnoreProperties(ignoreUnknown = true)
public class Foo {
    ...
}

Depending on the jackson version you are using you would have to use a different import in the current version it is:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

in older versions it has been:

import org.codehaus.jackson.annotate.JsonIgnoreProperties;

Answer 5

You can annotate the specific property in your POJO with @JsonIgnore.

Answer 6

it can be achieved 2 ways:

1. Mark the POJO to ignore unknown properties

   @JsonIgnoreProperties(ignoreUnknown = true)
   

2. Configure ObjectMapper that serializes/De-serializes the POJO/json as below:

   ObjectMapper mapper =new ObjectMapper();            
   // for Jackson version 1.X        
   mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
   // for Jackson version 2.X
   mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)