JsonProperty.Access.READ_ONLY not work

[GTxx]

I want to disable one field deserialization, so first I add annotaion JsonProperty to the field, but it still throw exception in deserialization process.

Then I tried JsonIgnoreProperties, and annotate the class with specified field, jackson ignores the field and works as expected.

Below is the code:

// User.java
import com.fasterxml.jackson.annotation.JsonProperty;

import java.util.Arrays;
import java.util.List;

public class User {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @JsonProperty(access = JsonProperty.Access.READ_ONLY)
    public List<String> getRoles() {
        return Arrays.asList("admin", "monitor");
    }
}

// User1.java
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

import java.util.Arrays;
import java.util.List;

@JsonIgnoreProperties(value={ "roles" }, allowGetters=true)
public class User1 {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<String> getRoles() {
        return Arrays.asList("admin", "monitor");
    }
}

// AppTest.java
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;

import static org.junit.Assert.assertTrue;

public class AppTest {
    @Test
    public void test1() throws Exception {
        User user = new User();
        user.setName("foo");
        ObjectMapper objectMapper = new ObjectMapper();
        String result;
        result = objectMapper.writeValueAsString(user);
        // will throw exception
        User deserizeUser = objectMapper.readValue(result, User.class);
    }

    @Test
    public void test2() throws Exception {
        User1 user = new User1();
        user.setName("foo");
        ObjectMapper objectMapper = new ObjectMapper();
        String result = objectMapper.writeValueAsString(user);
        assertTrue(result.contains("roles"));
        // Ok
        User1 deserilizeUser = objectMapper.readValue(result, User1.class);
    }
}

The first testcase will throw exception and it's stacktrace is:

com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.UnsupportedOperationException) (through reference chain: kk.User["roles"]->java.util.Arrays$ArrayList[2])

	at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:388)
	at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:360)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:211)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:20)
	at com.fasterxml.jackson.databind.deser.impl.SetterlessProperty.deserializeAndSet(SetterlessProperty.java:130)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
	at kk.AppTest.test1(AppTest.java:26)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.UnsupportedOperationException
	at java.util.AbstractList.add(AbstractList.java:148)
	at java.util.AbstractList.add(AbstractList.java:108)
	at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:198)
	... 29 more

[wwwcomy]

Facing the same problem, in issue #935, seems only simple types were handled correctly.

I looked into the code, the issue was caused by some special logic for USE_GETTERS_AS_SETTERS, in BeanDeserializerFactory Line 565 (version 2.8.10):

if (propDef.hasSetter()) {
                JavaType propertyType = propDef.getSetter().getParameterType(0);
                prop = constructSettableProperty(ctxt, beanDesc, propDef, propertyType);
            } else if (propDef.hasField()) {
                JavaType propertyType = propDef.getField().getType();
                prop = constructSettableProperty(ctxt, beanDesc, propDef, propertyType);
            } else if (useGettersAsSetters && propDef.hasGetter()) {
                /* May also need to consider getters
                 * for Map/Collection properties; but with lowest precedence
                 */
                AnnotatedMethod getter = propDef.getGetter();
                // should only consider Collections and Maps, for now?
                Class<?> rawPropertyType = getter.getRawType();
                if (Collection.class.isAssignableFrom(rawPropertyType)
                        || Map.class.isAssignableFrom(rawPropertyType)) {
                    prop = constructSetterlessProperty(ctxt, beanDesc, propDef);
                }
            }

By default USE_GETTERS_AS_SETTERS is enabled, so, although the Collection member was defined Access as "READ_ONLY", still, it is set as a property in the builder instance.

My work around is using (for spring boot applications) spring.jackson.mapper.USE_GETTERS_AS_SETTERS=false

However, I'm not sure this behavior is a bug or not, @cowtowncoder please help to clarify.

[cowtowncoder]

Yes, it sounds like this might be due to conflict between "getter-as-setter" (only used for Collections) and READ_ONLY modifier. I agree in that READ_ONLY should work consistently and prevent assignment, as per Javadocs.
So this sounds like a bug.

[clamothe]

Is any solution available for this, besides disabling USE_GETTERS_AS_SETTERS across the whole object mapper?

[cowtowncoder]

@clamothe No progress as of yet, but I'll try to add a test to verify. I have worked on a few issues related to READ_ONLY setting, which is rather tricky to make work as expected under different usage scenarios.

[cowtowncoder]

Oh. I think this is dup of #1382. Closing -- will fix both, but since that was filed earlier I'll keep that.

[clamothe]

Thanks! I'll test against 2.9.4.

Update:
It works. I was able to remove my workaround and my test serialization/deserialization test still passes, which failed under 2.9.3.

Old workaround was:
@JsonIgnoreProperties(value="fieldName", allowGetters=true)

[cowtowncoder]

I just released 2.9.4 so it should now be available generally (for anyone else reading).