CODEWITHSUNDEEP
javajsonjackson
Ted
Ted

Reputation: 20184

Serializing with Jackson (JSON) - getting "No serializer found"?

I get the an exception when trying to serialize a very simple object using Jackson. The error:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class MyPackage.TestA and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) )

Below is the simple class and code to serialize.

Can anyone tell my why I get this error?

public class TestA {
    String SomeString = "asd";
}

TestA testA = new TestA();
ObjectMapper om = new ObjectMapper();
try {
    String testAString = om.writeValueAsString(testA); // error here!

    TestA newTestA = om.readValue(testAString, TestA.class);
} catch (JsonGenerationException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (JsonMappingException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

Upvotes: 388

Views: 615208

Answers (24)

hiten
hiten

Reputation: 61

Add this in your application properties file

spring.jackson.serialization.FAIL_ON_EMPTY_BEANS=false

Upvotes: 6

Sumit Jadiya
Sumit Jadiya

Reputation: 767

Adding a getter/setter solved this problem for me. either manually add getter/setter or use Lombok annotations @Getter/@Setter/@Data for the same.

Upvotes: 4

Sham Fiorin
Sham Fiorin

Reputation: 539

I solved with @Getter from lombok

Upvotes: 4

j.xavier.atero
j.xavier.atero

Reputation: 584

For me, the problem was the annotation @RestResource(exported = false) from the import org.springframework.data.rest.core.annotation.RestResource. Which I forgot to remove.

Also, I got the same error when I forgot to add the class annotation @XmlRootElement from the import javax.xml.bind.annotation.XmlRootElement.

Upvotes: 0

Nakesh
Nakesh

Reputation: 576

Jackson uses getters and setters serialization./deserialization. So add getter and setter in your model class.

Upvotes: 11

Andriy Kryvtsun
Andriy Kryvtsun

Reputation: 3354

If you use Lomdok libraray (https://projectlombok.org/) then add @Data (https://projectlombok.org/features/Data) annotation to your data object class.

Upvotes: 0

Günay Gültekin
Günay Gültekin

Reputation: 4803

Add a

getter

and a

setter

and the problem is solved.

Upvotes: 165

saba
saba

Reputation: 498

in spring boot 2.2.5

after adding getter and setter

i added @JsonIgnore on top of the field.

Upvotes: 0

Vanita Dhotre
Vanita Dhotre

Reputation: 31

I just had only getters , after adding setters too , problems resolved.

Upvotes: 2

Satya Prakash
Satya Prakash

Reputation: 15

adding setter and getter will also solve the issue as it fixed for me. For Ex:

public class TestA {
    String SomeString = "asd";

    public String getSomeString () {        return SomeString ;     }

    public void setSomeString (String SS ) {        SomeString = SS ;   } 
}

Upvotes: 1

raveendra_bikkina
raveendra_bikkina

Reputation: 51

Please use this at class level for the bean:

@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler","fieldHandler"})

Upvotes: 2

Programmer Bruce
Programmer Bruce

Reputation: 66973

As already described, the default configuration of an ObjectMapper instance is to only access properties that are public fields or have public getters/setters. An alternative to changing the class definition to make a field public or to provide a public getter/setter is to specify (to the underlying VisibilityChecker) a different property visibility rule. Jackson 1.9 provides the ObjectMapper.setVisibility() convenience method for doing so. For the example in the original question, I'd likely configure this as

myObjectMapper.setVisibility(JsonMethod.FIELD, Visibility.ANY);

For Jackson >2.0:

myObjectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);

For more information and details on related configuration options, I recommend reviewing the JavaDocs on ObjectMapper.setVisibility().

Upvotes: 474

Janus
Janus

Reputation: 79

SpringBoot2.0 ，I resolve it by follow code:

@Bean public ObjectMapper objectMapper() {
 return new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);}

Upvotes: 7

Santhosh Kumar
Santhosh Kumar

Reputation: 31

Here are the three options:

  1. Data/class that's been accessed needs to be public
  2. If not public, add getters & setters
  3. Or add @JsonIgnore("context")

Upvotes: 3

georger
georger

Reputation: 1678

I found at least three ways of doing this:

  1. Add public getters on your entity that you try to serialize;
  2. Add an annotation at the top of the entity, if you don't want public getters. This will change the default for Jackson from Visbility=DEFAULT to @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY) where any access modifiers are accepted;
  3. Change your ObjectMapper globally by setting objectMapperInstance.setVisibility(JsonMethod.FIELD, Visibility.ANY);. This should be avoided if you don't need this functionality globally.

Choose based on your needs.

Upvotes: 5

Pavan Kumar
Pavan Kumar

Reputation: 4820

I had the same problem for a child class where I had control, object mapper was in a common module and was inaccessible. I solved it by adding this annotation for my child class whose object was to be serialized.

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)

Upvotes: 11

yellow
yellow

Reputation: 455

Though I added getters and setters I was getting the same error. Later I found a bug, that is by Sonar's advice I cgahnged the getters and setters as protected which was causing the issue. Once I fixed that it worked as exppected.

Upvotes: 0

Chris
Chris

Reputation: 23181

For Jackson to serialize that class, the SomeString field needs to either be public (right now it's package level isolation) or you need to define getter and setter methods for it.

Upvotes: 93

LEMUEL ADANE
LEMUEL ADANE

Reputation: 8836

For Oracle Java applications, add this after the ObjectMapper instantiation: 

mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);

Upvotes: 3

Sanchit Singhania
Sanchit Singhania

Reputation: 527

The problem may be because you have declared variable as private. If you change it to public, it works.

Better option is to use getter and setter methods for it.

This will solve the issue!

Upvotes: 3

Martín C
Martín C

Reputation: 1077

The problem in my case was Jackson was trying to serialize an empty object with no attributes nor methods.

As suggested in the exception I added the following line to avoid failure on empty beans:

For Jackson 1.9

myObjectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);

For Jackson 2.X

myObjectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);

You can find a simple example on jackson disable fail_on_empty_beans

Upvotes: 43

N. berouain
N. berouain

Reputation: 1321

I had a similar problem with lazy loading via the hibernate proxy object. Got around it by annotating the class having lazy loaded private properties with:

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})

Upvotes: 5

ZiglioUK
ZiglioUK

Reputation: 2610

If you can edit the class containing that object, I usually just add the annotation

import com.fasterxml.jackson.annotation.JsonIgnore;

@JsonIgnore 
NonSerializeableClass obj;

Upvotes: 9

patrics
patrics

Reputation: 788

This error is also thrown if you forget to add the .build() method onto your return status.

return Response.status(Status.OK);         // fails
return Response.status(Status.OK).build(); // works

I got the following error without build() method:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class com.sun.jersey.core.spi.factory.ResponseBuilderImpl

Upvotes: 8

Related Questions