Jersey/Jackson @JsonIgnore on setter

Question

i have an class with the following annotations:

class A {
public Map<String,List<String>> references;

@JsonProperty
public Map<String,List<String>> getReferences() {
...
}

@JsonIgnore
public void setReferences(Map<String,List<String>>) {
}
...
}
}

What I try is to ignore the json on deserialization. But it doesn't work. Always when JSON String arrives the Jackson lib fill the references attribute. If I use only the @JsonIgnore annotation the getter doesn't work. Are there any solutions for this problem?

Thanks

score 16 · Answer 1 · answered Feb 11 '13 at 23:59

I think there are two key pieces that should enable you to have "read-only collections" as desired. First, in addition to ignoring the setter, ensure that your field is also marked with @JsonIgnore:

class A {

  @JsonIgnore
  public Map<String,List<String>> references;

  @JsonProperty
  public Map<String,List<String>> getReferences() { ... }

  @JsonIgnore
  public void setReferences(Map<String,List<String>>) { ... }

}

Second, in order to prevent the getters from being used as setters, disable the USE_GETTERS_AS_SETTERS feature:

ObjectMapper mapper = new ObjectMapper();
mapper.disable(MapperFeature.USE_GETTERS_AS_SETTERS);

I foolishly ignored your first advice and doesn't marked the field as ignored, since it is private in my case. However, I needed to do that nevertheless, to get it working properly. Is this right or a misunderstanding on my side? If so, maybe it's worth pointing that out explicitly in your answer. — Tim Büthe, Nov 19 '14 at 10:13

score 16 · Answer 2 · answered Feb 13 '18 at 08:54

As of Jackson 2.6, there is a new and improved way to define read-only and write-only properties, using JsonProperty#access() annotation. This is recommended over use of separate JsonIgnore and JsonProperty annotations.

@JsonProperty(access = JsonProperty.Access.READ_ONLY)
public Map<String,List<String>> references;

Alexander Burakevych · Answer 3 · 2014-11-28T00:47:14.430

You have to make sure there is @JsonIgnore annotation on the field level as well as on the setter, and getter annotated with @JsonProperty.

public class Echo {

    @Null
    @JsonIgnore
    private String doNotDeserialise;

    private String echo;

    @JsonProperty
    public String getDoNotDeserialise() {
        return doNotDeserialise;
    }

    @JsonIgnore
    public void setDoNotDeserialise(String doNotDeserialise) {
        this.doNotDeserialise = doNotDeserialise;
    }

    public String getEcho() {
        return echo;
    }

    public void setEcho(String echo) {
        this.echo = echo;
    }
}

@Controller
public class EchoController {

@ResponseBody
@RequestMapping(value = "/echo", consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
    public Echo echo(@RequestBody @Valid Echo echo) {
        if (StringUtils.isEmpty(echo.getDoNotDeserialise())) {
            echo.setDoNotDeserialise("Value is set by the server, not by the client!");
        }

        return echo;
    }
}

If you submit a JSON request with a “doNotDeserialise” value set to something, when JSON is deserialised to an object it will be set to null (if not I put a validation constraint on the field so it will error out)
If you set the “doNotDeserialise” value to something on the server then it will be correctly serialised to JSON and pushed to the client

score 3 · Answer 4 · answered Apr 03 '15 at 23:27

I used @JsonIgnore on my getter and it didn't work and I couldn't configure the mapper (I was using Jackson Jaxrs providers). This worked for me:

@JsonIgnoreProperties(ignoreUnknown = true, value = { "actorsAsString",
    "writersAsString", "directorsAsString", "genresAsString" })

score 0 · Answer 5 · edited May 23 '17 at 11:54

0

I can only think of a non-jackson solution, to use a base class that does not have references for the mapping and then cast to the actual class:

// expect a B on an incoming request
class B {
// ...
}

// after the data is read, cast to A which will have empty references
class A extends B {
public Map<String,List<String>> references;
}

Why do you even send the References if you don't want them?

Or is the incoming data out of your hands and you just want to avoid the mapping exception telling you that jackson cannot find a property to set for incoming references? For that we use a base class which all of our Json model classes inherit:

public abstract class JsonObject {

    @JsonAnySetter
    public void handleUnknown(String key, Object value) {

        // for us we log an error if we can't map but you can skip that
        Log log = LogFactory.getLog(String.class);    
        log.error("Error mapping object of type: " + this.getClass().getName());    
        log.error("Could not map key: \"" + key + "\" and value: \"" + "\"" + value.toString() + "\"");

    }

Then in the POJO you add @JsonIgnoreProperties so that incoming properties will get forwarded to handleUnknown()

@JsonIgnoreProperties
class A extends JsonObject {
    // no references if you don't need them
}

edit

This SO Thread describes how to use Mixins. This might be the solution, if you want to keep your structure exactly as it is, but I have not tried it.

edited May 23 '17 at 11:54

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answered Sep 26 '12 at 06:17

Pete

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That's right. The incoming data is not really in our hands. But the clients sends always references attribute in correct format so handleUnknown will never be called. – guerilla Sep 26 '12 at 07:51
Ah, my bad, forgot a little pice of information. You need `@JsonIgnoreProperties` at the POJO if you want to ignore incoming data. I'll update my post. (PS: we use this to consume facebook's REST resource and all properties sent from facebook that are not contained in our POJO will just get logged and then we decide if we want to add them or not) – Pete Sep 26 '12 at 09:55
But references is in my POJO so it always matches to the setter – guerilla Sep 26 '12 at 16:11
But why do you keep References in your POJO if you don't need it? Found another solution that might be applicable if you really want to keep your exact structure: http://stackoverflow.com/questions/7421474/how-can-i-tell-jackson-to-ignore-a-property-for-which-i-dont-have-control-over – Pete Sep 26 '12 at 17:28
Thanks for the link. I've tried mixins before and it works not for me. The challenge is getting the references property to Read-only state. So that I can send information to the client but ignore incoming changes on this property – guerilla Sep 27 '12 at 04:41

Jersey/Jackson @JsonIgnore on setter

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