Should never call `set()` on setterless property during deserialization

[luca boncompagni]

Hi,

I have something like the following code:

@JsonIgnoreProperties(ignoreUnknown = true)
public class DataBean {

 private final String val;

 @JsonCreator
 public DataBean(@JsonProperty(value = "val") String val) {

                 this.val = val;

 }

 public String getVal() {
                 return val;

 }
 
 public List<String> getList(){
                 return new ArrayList<>();

 }


 @Override
 public String toString() {
                 return "DataBean [val=" + val + "]";

 }
 public static void main(String[] args) throws Exception {
                 ObjectMapper om = new ObjectMapper();

                 String json;

                 DataBean out;

                  json = "{\"list\":[\"11\"],\"val\":\"VAL2\"}";

                 out = om.readerFor(DataBean.class).readValue(json);

                 System.out.println("this is ko" + out);

 }
}

When I run the test I get: "java.lang.UnsupportedOperationException: Should never call `set()` on setterless property ('list')". If I modify the JSON, having the value of the constructor as first field, it runs OK. 

         json = "{\"val\":\"VAL2\",\"list\":[\"11\"]}";
         out = om.readerFor(DataBean.class).readValue(json);
         System.out.println("this is ok: " + out);

I know that I can solve it setting MapperFeature.USE_GETTERS_AS_SETTERS to false, but I can't. 

In order to solve the issue, I try the following orrible patch:

diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/impl/SetterlessProperty.java b/src/main/java/com/fasterxml/jackson/databind/deser/impl/SetterlessProperty.java

index 9c80e49..ca7ec85 100644

--- a/src/main/java/com/fasterxml/jackson/databind/deser/impl/SetterlessProperty.java

+++ b/src/main/java/com/fasterxml/jackson/databind/deser/impl/SetterlessProperty.java

@@ -3,6 +3,8 @@

 import java.io.IOException;

 import java.lang.annotation.Annotation;

 import java.lang.reflect.Method;

+import java.util.Collection;

+import java.util.List;

 

 import com.fasterxml.jackson.core.JsonParser;

 import com.fasterxml.jackson.core.JsonToken;

@@ -144,7 +146,21 @@

 

     @Override

     public final void set(Object instance, Object value) throws IOException {

-        throw new UnsupportedOperationException("Should never call `set()` on setterless property ('"+getName()+"')");

+    if(value instanceof Collection) {

+   

+    Collection<Object> collection = (Collection<Object>) value;

+ Collection<Object> toModify;

+    try {

+    toModify = (Collection<Object> )_getter.invoke(instance, (Object[]) null);

+    toModify.addAll(collection);

+    } catch (Exception e) {

+    _throwAsIOE((JsonParser)null, e);

+    return; // never gets here

+    }

+   

+    } else {

+    throw new UnsupportedOperationException("Should never call `set()` on setterless property ('"+getName()+"')");

+    }

     }

 

     @Override+    Collection<Object> collection = (Collection<Object>) value;

Is there any other way or patch to solve it?

Thanks,

Luca 

[Tatu Saloranta]

Hi there! I suggest you file a github issue for `jackson-databind`,
with all information from above.
I can't say if it is a bug without digging deeper, and right now it
may take a while for me to find time.
But once I have time I'll have a look and hopefully we can resolve the
issue, whatever it is.

-+ Tatu +-