Serializing with Jackson (JSON) - getting "No serializer found"?
JavaJsonJacksonJava Problem Overview
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();
}
Java Solutions
Solution 1 - Java
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()
.
Solution 2 - Java
Add a > getter
and a
> setter
and the problem is solved.
Solution 3 - Java
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.
Solution 4 - Java
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 https://stackoverflow.com/questions/15261456/jackson-disable-fail-on-empty-beans
Solution 5 - Java
If you can edit the class containing that object, I usually just add the annotation
import com.fasterxml.jackson.annotation.JsonIgnore;
@JsonIgnore
NonSerializeableClass obj;
Solution 6 - Java
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)
Solution 7 - Java
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
Solution 8 - Java
SpringBoot2.0 ,I resolve it by follow code:
@Bean public ObjectMapper objectMapper() {
return new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);}
Solution 9 - Java
Jackson uses getters and setters serialization./deserialization. So add getter and setter in your model class.
Solution 10 - Java
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"})
Solution 11 - Java
For Oracle Java applications, add this after the ObjectMapper
instantiation:
mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
Solution 12 - Java
I found at least three ways of doing this:
- Add
public getters
on your entity that you try to serialize; - Add an annotation at the top of the entity, if you don't want
public getters
. This will change the default for Jackson fromVisbility=DEFAULT
to@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
where any access modifiers are accepted; - Change your
ObjectMapper
globally by settingobjectMapperInstance.setVisibility(JsonMethod.FIELD, Visibility.ANY);
. This should be avoided if you don't need this functionality globally.
Choose based on your needs.
Solution 13 - Java
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!
Solution 14 - Java
Here are the three options:
- Data/class that's been accessed needs to be
public
- If not
public
, add getters & setters - Or add
@JsonIgnore("context")
Solution 15 - Java
Please use this at class level for the bean:
@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler","fieldHandler"})
Solution 16 - Java
I just had only getters , after adding setters too , problems resolved.
Solution 17 - Java
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 ; }
}
Solution 18 - Java
in spring boot 2.2.5
after adding getter and setter
i added @JsonIgnore on top of the field.
Solution 19 - Java
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.
Solution 20 - Java
If you use Lomdok libraray (https://projectlombok.org/) then add @Data
(https://projectlombok.org/features/Data) annotation to your data object class.